Rash — Medicine Library

Quick guide

Diagnostic approach

Focused clinical evaluation, including comprehensive skin examination
CBC
CMP
See “Diagnostics for rash.”

Routine laboratory studies are seldom required for rashes that appear benign, but are necessary in severely ill patients.

Management checklist

Don PPE.
Isolate patients with fever and petechial rash and use droplet precautions.
For life-threatening rash, establish IV and consult dermatology urgently.
Supportive care for symptom relief
Manage the underlying cause.
Admit patients with vital sign abnormalities, systemic infection or syndrome, electrolyte abnormalities, inability to maintain PO intake.

Red flag features

Fever
Severely ill appearance
Hypotension
Severe pain
Mucosal lesions
Extremes of age
History of immunosuppression
Recently initiated medication

Life-threatening causes

Toxic epidermal necrolysis
Stevens-Johnson syndrome
Necrotizing fasciitis
Meningococcal septicemia
Toxic shock syndrome
Disseminated intravascular coagulation
Anaphylaxis
Rocky Mountain spotted fever
DRESS
Pemphigus vulgaris

Summary

Rash is a common presenting symptom with many different causes. A systematic approach is necessary to identify life-threatening conditions and reach a definitive diagnosis. Initial management steps include evaluating for red flags for a life-threatening rash and characterizing the rash based on its basic morphology, e.g., petechial or purpuric, erythematous, maculopapular, annular, or vesiculobullous. The cause of rash can often be identified clinically, but specific testing may be required based on the presumptive diagnosis. Management is specific to the condition. Although most rashes can affect individuals of any age, some are more common in childhood (e.g., pediatric viral exanthems).

For details on rashes or lesions due to localized infection, see “Overview of skin and soft tissue infections.”

Etiology

Petechial and purpuric rashes

Febrile or severely ill patients

Palpable lesion
- Meningococcal septicemia
- Disseminated gonococcal infection
- Acute bacterial endocarditis
- Rocky Mountain spotted fever (RMSF)
- IgA vasculitis
Nonpalpable lesion
- Thrombotic thrombocytopenic purpura (TTP)
- Purpura fulminans
- Acute leukemia [3]

Afebrile patients

Palpable lesion: vasculitis
Nonpalpable lesion: idiopathic thrombocytopenia (ITP)

Purpura in IgA vasculitis Purpura Petechial bleeding due to thrombocytopenia

Erythematous rashes

Febrile or severely ill patients

Positive
Nikolsky sign
- Staphylococcal scalded skin syndrome (SSSS)
- Stevens-Johnson syndrome (SJS)
- Toxic epidermal necrolysis (TEN)
Negative
Nikolsky sign
- Toxic shock syndrome (TSS)
- Kawasaki disease
- Scarlet fever

Afebrile patients

Positive Nikolsky sign: Toxic epidermal necrolysis
Negative
Nikolsky sign
- Anaphylaxis
- Histamine fish poisoning
- Medication flushing syndrome, e.g., vancomycin, niacin
- Alcohol flush reaction

Vancomycin flushing reaction

Maculopapular rashes

Febrile or severely ill patients

Central distribution
- Measles
- Viral exanthem
- Lyme disease
- Drug reaction with eosinophilia and systemic symptoms (DRESS syndrome)
Peripheral distribution
- Erythema multiforme
- Meningococcal septicemia
- RMSF
- Syphilis
- Lyme disease

Afebrile patients

Central distribution
- Drug reaction
- Pityriasis rosea
Peripheral distribution
- Scabies
- Atopic dermatitis
- Bed bugs [4]

Measles

Vesiculobullous rashes

See “Overview of blistering skin diseases.”

Febrile or severely ill patients

Diffuse distribution
- Varicella
- Disseminated intravascular coagulation (DIC)
- Disseminated gonococcal infection
- Smallpox
Localized distribution
- Necrotizing fasciitis
- Hand foot and mouth disease

Afebrile patients

Diffuse distribution
- Bullous pemphigoid
- Pemphigus vulgaris
Localized distribution
- Herpes zoster
- Contact dermatitis
- Burns
- Dyshidrotic eczema

Chickenpox

Annular skin lesions [5]

Tinea infections
Nummular dermatitis
Erythema marginatum
Erythema multiforme
Fixed drug eruption
Granuloma annulare
Subacute cutaneous lupus erythematosus

Tinea corporis

Skin plaques and scaling lesions [6]

Psoriasis
Seborrheic dermatitis
Cutaneous lichen planus
Pityriasis rubra pilaris
Mycosis fungoides
Erythroderma
Tinea infections
See also “Differential diagnosis of scaling.”

Psoriasis

Urticaria [7]

See also “Type I hypersensitivity reaction.”

Acute (< 6 weeks): viral infection, drug reactions, or food allergens
Chronic (
≥ 6 weeks)
- Spontaneous urticaria
- Chronic inducible urticaria

Urticaria

Childhood rashes [8][9]

See also “Differential diagnosis of infectious rashes in childhood.”

Infectious rashes in children

Common causes

Roseola infantum
Pityriasis rosea
Scarlet fever
Erythema infectiosum
Hand foot and mouth disease
Nonbullous impetigo
Atopic dermatitis
Contact dermatitis
Exanthematous cutaneous reaction [10][11]
Scabies
Tinea infections

Less common causes

Varicella zoster (chickenpox)
Measles
Rubella
Erysipelas
SSSS
SJS/TEN
Acute generalized exanthematous pustulosis
DRESS
RMSF

**Purpura in IgA vasculitis**
Photograph of the leg of an 18-year-old male patient
Multiple well-defined erythematous skin lesions (purpura) are visible. Some purpura have coalesced to form ecchymoses. Examination revealed the purpura to be palpable and nonblanchable.
The tetrad of purpura, arthritis, abdominal pain, and kidney impairment is typical of IgA vasculitis. Histopathology is required to confirm the diagnosis of IgA vasculitis.

Source: “Purpura” by Hektor, Wikimedia Commons, licensed under CC BY-SA 3.0.

**Purpura**
Bluish-red, round or oval maculae (approx. 0.2 mm–1 cm in diameter) are distributed over the right lower leg. There is also an irregularly shaped macula of the same color lateral to the patella (approx. 4 × 2 cm in diameter).
This appearance is characteristic of purpura.

Source: © IMPP

**Petechial bleeding due to thrombocytopenia**
The lower leg displays numerous red spots, each about the size of a pinhead, that do not blanch or disappear when pressed. These are indicative of petechial hemorrhages related to thrombocytopenia.

Source: © IMPP

**Vancomycin flushing reaction**
Erythema of the skin is visible, especially on the patient's cheeks and nose. This symptom usually resolves within minutes after treatment. Vancomycin flushing reaction is not a true allergic reaction, but rather a rate-dependent hypersensitivity reaction. It can be avoided by slow infusion.

Source: “Figure 1, in: Red Man Syndrome with Oral Vancomycin: A Case Report” by Fray Arroyo-Mercado, Aleksandr Khudyakov, Gurasees S. Chawla, Onix Cantres-Fonseca, and Isabel M. McFarlane, American Journal of Medical Case Reports, licensed under CC BY 4.0.

**Measles**
Dark red, large maculopapular, partially confluent exanthema on patient's back.
Combined with the characteristic clinical features, this finding indicates measles.

Source: Courtesy of Dr. Gary M. White, MD

**Chickenpox**
Chest of a child
Multiple vesicles filled with clear fluid on an erythematous base are visible.
This clinical finding is called "dewdrops on a rose petal," and it is classically seen in varicella (chickenpox).

Source: Courtesy of Dr. Gary M. White, MD

**Tinea corporis**
A round, well demarcated erythematous lesion with central scaling is visible. The border is raised with several pustules visible.
These features are characteristic of tinea corporis.

Source: "ID#: 2938", CDC/ Dr. Lucille K. Georg, Centers for Disease Control and Prevention (CDC) licensed under Public Domain

**Psoriasis**
Well-demarcated erythematosquamous plaques and silver-white scaling are visible over the extensor side of both lower legs.
These findings are characteristic of psoriasis.

Source: © IMPP

**Urticaria**
Erythematous, confluent plaques typical of urticaria that cover most of the skin on the antecubital fossa and the ventral side of the forearm.

Source: “EMminor2010” by James Heilmann, MD, Wikimedia Commons, licensed under CC BY-SA 3.0.

**Infectious rashes in children**
Many infectious diseases in children present with a rash (exanthem). The distribution and morphological characteristics of the exanthem allow the diseases to be differentiated from one another.

Measles: Patients present with a dark red, erythematous, maculopapular, partially confluent exanthem, which spreads from behind the ears to the rest of the body.

Scarlet fever: Patients present with a fine, light red rash with sandpaper-like texture. The exanthem begins on the neck or trunk and disseminates to the whole body. Cheeks may be flushed with perioral pallor. In flexural areas (e.g., axilla and groin), the rash may be more pronounced and linear petechiae (Pastia lines) may be present.

Rubella (German measles): Patients typically present with a nonconfluent, pink, maculopapular exanthem, which begins on the face and spreads to the trunk and extremities.

Erythema infectiosum (fifth disease): A confluent, maculopapular rash appears only in ¼ of patients. It may take on a lace-like, reticular appearance over time. Additionally, patients present with diffuse redness of the face with perioral sparing (slapped-cheek rash).

Roseola infantum (sixth disease): 3-7 days of high fever are followed by a sudden decrease in temperature and development of a patchy, blanching rose-pink maculopapular rash. The rash originates on the trunk, and may spread to the face and extremities.

Varicella (chickenpox): The exanthem affects the whole body, typically spreading to the scalp as well. Various stages of the rash occur simultaneously, which leads to the characteristic clinical finding known as “starry sky.”

© AMBOSS

Initial management

Approach [1][2][12]

Don PPE as appropriate, e.g., contact precautions.
Isolate patients with fever and petechial rash and escalate PPE to droplet precautions.
Identify patients with
red flags for a life-threatening rash.
- Initiate continuous monitoring and place IV access in severely ill patients.
- Consult dermatology urgently.
Initiate treatment for life-threatening causes of rash immediately.
Perform a focused clinical evaluation.
Narrow the differential diagnosis based on the morphology of the rash (see “Etiology”).
Obtain appropriate diagnostic testing.
Begin supportive and definitive treatment.

Fever and petechial rash may indicate meningococcal septicemia.

Red flags for a life-threatening rash [2]

Fever
Severely ill appearance, e.g., lethargy, cyanosis, mottled extremities, hypoventilation or hyperventilation
Hypotension
Mucosal lesions
Severe pain
Extremes of age
History of immunosuppression
Recently initiated medication

Life-threatening causes of rash

Pemphigus vulgaris
SJS/TEN
DRESS
TSS
Meningococcal septicemia
RMSF
Necrotizing fasciitis

Disposition [4]

Admit patients with any of the following:

Hypotension
High fever or hypothermia
Systemic infection or underlying condition requiring inpatient management
Significant fluid and electrolyte abnormalities
Inability to maintain oral intake

Clinical evaluation

The differential diagnosis of a rash can be quickly narrowed using basic morphology and associated clinical findings. [1][2]

Focused history [2][8][12]

Rash characteristics

Onset
Duration
Progression

Associated symptoms

Fever
Pruritus
Pain at rash site
Arthralgias

Exposures

New medications
Recent travel
Occupation
Change in personal care products
Sexual history
Sick contacts
Recent bites

Focused examination [2][4][12]

General physical examination

Overall condition, e.g., mental status and vital signs
Lung auscultation
Cardiac auscultation
Lymphadenopathy

Skin examination

See “Primary skin lesions” and “Secondary skin lesions” for describing and documenting rashes.

Rash morphology
- Petechiae or purpura
- Erythema
- Maculopapular rash
- Vesiculobullous rash
Lesion characteristics
- Palpable or nonpalpable
- Blanchable
- Positive or negative Nikolsky sign

Always have the patient disrobe and ensure that the entire body is examined, including mucus membranes and genitalia.

Diagnosis

Laboratory studies [4][12]

Routine laboratory studies are seldom required for rashes that appear benign, but are necessary in severely ill patients.

CBC
- Thrombocytopenia, e.g., in vasculitis
- Leukocytosis suggests infection or severe inflammatory disease.
CMP
- Electrolyte and acid-base abnormalities suggest severe disease.
- Abnormal LFTs may indicate hepatitis, e.g., in severe drug reactions.
Serology,
antibody, and
antigen testing

Rapid strep test: often positive in scarlet fever

EBV serology: positive in infectious mononucleosis

Monospot test: positive in infectious mononucleosis, but may be false positive

VDRL or FTA-ABS: diagnostic for syphilis

Rickettsia antibody panels

Lyme antibody testing

ANCA: for suspected autoimmune conditions, e.g., eosinophilic granulomatosis with polyangiitis
Cultures: CSF for meningococcal septicemia, blood cultures for endocarditis

Dermatologic studies

Punch biopsy: for uncertain diagnosis or suspected autoimmune condition
Tzanck smear: in vesicular lesions; diagnostic for pemphigus vulgaris, HSV infection, and chickenpox
Vesicle or pustule cultures: for suspected bacterial, fungal, or viral infections
Patch test: for suspected contact dermatitis, allergic dermatitis
KOH prep: for suspected fungal infections

Petechial and purpuric rashes

The lesions of a petechial or purpuric rash do not blanch when pressure is applied.

Common causes of petechial and purpuric rashes [2][3][13]
	Images	Distinguishing features	Diagnostic findings	Management
Meningococcal septicemia		Palpable rash Fever Symptoms of meningitis [3]	Positive CSF and/or blood cultures	Immediate stabilization for meningitis, isolation precautions Immediate empiric antibiotics for bacterial meningitis See “Management of meningitis.”
Acute bacterial endocarditis		Palpable rash High fever Malaise, fatigue Splinter hemorrhages Janeway lesions Osler nodes Cardiac murmur	Valve lesion on echocardiogram Positive blood cultures	Empiric antibiotic therapy for infective endocarditis See “Management of infective endocarditis.”
RMSF		Palpable rash Fever Headaches Myalgias	Clinical diagnosis supported by laboratory studies [14]	Immediate empiric antibiotic therapy See “Treatment” in “RMSF.”
Disseminated gonococcal infection		Palpable rash Fever Arthralgias Petechiae that progress to pustules	Positive culture from blood, urethral, cervix, and/or skin lesion	Antibiotic therapy for gonorrhea See “Management of gonorrhea.”
IgA vasculitis		Palpable rash Fever Arthralgias Abdominal pain	Clinical diagnosis supported by laboratory studies Findings indicating nephritis	Fluid therapy Glucocorticoids, IVIg See “Treatment of IgA vasculitis.”
TTP		Nonpalpable rash Fever Altered mental status Signs of hemolytic anemia	CBC: ↓ platelets, ↓ hemoglobin Coagulation studies: normal pTT Urinalysis: hematuria, proteinuria	Hematology consult Plasma exchange See “Treatment of TTP.”
ITP		Nonpalpable rash No fever Mild mucosal or cutaneous bleeding	Thrombocytopenia	Glucocorticoids, IVIg See “Treatment of ITP.”
Vasculitic syndromes		Palpable rash Patients are often afebrile and appear well.	Thrombocytopenia ↑ ESR and CRP	Immunosuppressive therapy See “Vasculitides.”

Unexplained purpura in a child, especially on the trunk, ears, or face, may indicate child abuse. [3]

**Purpura in Waterhouse-Friderichsen syndrome**
Purple nonblanching macules of various sizes, consistent with purpura (larger macules) and petechiae (smaller macules), are visible.
These findings are consistent with purpura in Waterhouse-Friderichsen syndrome.

Source: © IMPP

**Osler nodes**
There are multiple raised nodular lesions on the palm and palmar aspects of the first and second digits. The lesions appear dark brown, indicating subcutaneous hemorrhages.
This is the typical appearance of Osler nodes.

Source: “Osler Nodules Hand” by Roberto J. Galindo, Wikimedia Commons, licensed under CC BY-SA 4.0.

**Janeway lesions**
Multiple erythematous macules are visible on the thenar eminence and the base of the thumb.
These Janeway lesions are typically caused by septic microembolisms secondary to infective endocarditis.

Source: “Janeway lesion” by Warfieldian, Wikimedia Commons, licensed under CC BY-SA 4.0.

**Rocky Mountain spotted fever rash**
Multiple, partly confluent, macules are visible on this patient's forearm.
This rash is suggestive of Rocky Mountain spotted fever (RMSF), a tick-borne disease caused by Rickettsia rickettsii bacteria. The distal extremities are usually affected first; the rash then spreads toward the proximal extremities and the trunk (the face, however, is usually spared).

Source: "ID#: 1962", CDC, Centers for Disease Control and Prevention licensed under Public Domain

**Skin lesion in disseminated gonococcal infection**
Source: "ID#: 2848", CDC/Dr. Thomas F. Sellers, Public Health Image Library (PHIL) licensed under Public Domain

**Cryoglobulinemic vasculitis**
Multiple, partially confluent, round circular maculae (purpura) can be seen on both lower legs and thighs.
This is a common cutaneous symptom of cryoglobulinemic vasculitis.

Source: © IMPP

Diffuse erythematous rashes

Erythematous rashes manifest as diffuse redness that blanches with pressure.

Common causes of erythematous rashes [2][4]
	Images	Distinguishing features	Diagnostic findings	Management
SSSS		Fever Patient appears severely ill. Tender rash, later bullous Positive Nikolsky sign	Leukocytosis Findings of organ failure on CMP Positive blood cultures and/or cultures from the suspected source of infection	Fluid therapy Empiric antibiotics See “Management of SSSS.”
TEN and SJS [15]		Fever is common. Patient appears severely ill. Mucus membrane involvement Evolves to bullous rash over 5–7 days Positive Nikolsky sign Designation depends on body surface area involvement: < 10%: SJS 10–30%: SJS/TEN > 30%: TEN	Leukocytosis Findings of organ failure on CMP Characteristic features on skin biopsy	Discontinue offending medications. Initiate burn management. Consider transfer to a burn center. See “Treatment of SJS and TEN.”
TSS		Fever Signs of shock Nonexudative mucosal inflammation Negative Nikolsky sign Desquamation occurs after several days.	Diagnostic findings of sepsis	Immediate hemodynamic support Empiric antibiotic therapy for TSS See “Management of TSS.”
Scarlet fever rash		Fever Malaise Sore throat Negative Nikolsky sign Fine papules	Positive rapid strep test Throat culture	Empiric antibiotics See “Management of scarlet fever.”
Anaphylaxis		Features of anaphylaxis No fever Negative Nikolsky sign	Clinical diagnosis Elevated serum tryptase	IV or IM epinephrine IV fluid resuscitation See “Management of anaphylaxis.”
Histamine fish poisoning [16]		History of ingesting dark-meat fish No fever Pruritus and urticaria Burning sensation in mouth Negative Nikolsky sign	Clinical diagnosis	Antihistamines Epinephrine (if symptoms are severe) See “Histamine fish poisoning.”
Flushing reaction [17][18]		Previous exposure to alcohol or a triggering drug, e.g., vancomycin, niacin No fever Negative Nikolsky sign Pruritus	Clinical diagnosis	Antihistamines Discontinue or slow infusion of triggering medication.

**Staphylococcal scalded skin syndrome**
Perioral, cervical and axillary reddening of the skin is visible, resulting in a scalded appearance on this child's face. In some areas, the superficial epidermal layer is detached (e.g., on the chin). On the right side of the neck, several flaccid blisters can be seen. The lips appear dry, with several rhagades in the corners of the mouth.

Source: Courtesy of Dr. Gary M. White, MD

**Toxic epidermal necrolysis (TEN)**
The trunk and arm show generalized, widespread, extensive necrosis with purple and red erythema, as well as yellow-white exudation. Spots of hemorrhagic, subepidermal tissue can also be seen.
These characteristic findings are distinctive for TEN, a severe form of Stevens-Johnson syndrome (SJS).

Source: “Figure 89: Extensive epidermal necrolysis; in : Atlas of Pediatric HIV Infection” by Regina E. Oladokun; Rannakoe J. Lehloenya; Carol Hlela et al., Openbooks, licensed under CC BY-ND 4.0.

© Massachusetts Medical Society. All rights reserved. AMBOSS SE, exclusive licensee.

**Skin manifestations in scarlet fever**
The typical scarlet-colored, fine, maculopapular exanthem of scarlet fever is seen on the right arm. Flushed cheeks and perioral pallor are also evident.

Source: “Scarlet Fever” by Badobadop, Wikimedia Commons, licensed under CC BY-SA 3.0. Modifications: Pixelated eyes.

**Urticaria (hives)**
Multiple annular, erythematous, well-demarcated, slightly elevated plaques are visible.
This appearance is consistent with urticaria. Urticaria appears soon after exposure to an antigen and disappears within a few hours. The lesions are caused by mast-cell degranulation in the superficial dermis.

Our great thanks to Milena Koreng for kindly providing this image.

Maculopapular rashes

The mixture of flat and raised discolored areas that define a maculopapular rash may also be the early stage of a petechial, purpuric, or vesiculobullous rash.

Common causes of maculopapular rashes [2][4]
	Images	Distinguishing features	Diagnostic findings	Management
Measles		Prodrome of fever and malaise “3 Cs”: cough, coryza, and conjunctivitis Blanching rash Koplik spots	Positive measles serology and/or PCR	Respiratory and contact isolation Supportive therapy Vitamin A supplementation See “Management of measles.”
Kawasaki disease		Fever Cervical lymphadenopathy Conjunctival injection Strawberry tongue Peripheral edema	↑ Inflammatory markers Variable ECG changes	IVIg Aspirin See “Management of Kawasaki disease.”
Secondary syphilis		Diffuse reddish-brown or copper lesions on the trunk and extremities Potentially fever and/or malaise Occurs weeks to months after resolution of the initial chancre	Positive nontreponemal tests, e.g., RPR, VDRL Positive treponemal tests, e.g., FTA-ABS	Antibiotics for syphilis See “Treatment of syphilis.”
Viral exanthem		Variable presentation Typically nonpruritic Does not desquamate	Typically a clinical diagnosis	See “Infectious rashes in childhood.”
Cutaneous drug reactions [10][11]		Usually pruritic Begin on the trunk and spread to the extremities Symmetrical distribution	Clinical diagnosis	Discontinue inciting medication. Antihistamines
Scabies		Elongated papules Typically affects interdigital folds, intertriginous areas, and wrists Pruritic	Dermoscopic visualization of mites, larvae, ova, or mite feces	Scabicidal agents See “Treatment of scabies.”
Atopic dermatitis		Dry, scaly rash Infants: cheeks, scalp, extensor areas Children and adults: antecubital fossa, extensor areas Intense pruritus	Clinical diagnosis	Topical emollients Topical corticosteroids See “Treatment of atopic dermatitis.”
Pityriasis rosea	Pityriasis rosea may appear as an annular lesion or in a maculopapular distribution; see “Annular skin lesions.”

Meningococcal septicemia, RMSF, and Stevens-Johnson syndrome are life-threatening conditions that may also cause a maculopapular rash.

**Typical findings in Kawasaki disease**
(A) Bilateral, nonpurulent conjunctivitis
(B) Stomatitis with bright red lips
(C) Erythema and edema of the hands
(D) Erythema and edema of the feet
(E) Truncal rash
(F) Cervical lymphadenopathy
(G) Ultrasound of an enlarged cervical lymph node: increased perfusion
(H) Desquamation of fingertips
(I) Deep grooves in the nail (Beau lines)

Source: “Figure 2, in: Kawasaki Disease” by C. M. Hedrich, A. Schnabel, T. Hospach, Frontiers in Pediatrics, licensed under CC BY 4.0.

**Maculopapular rash in secondary syphilis**
An erythematous maculopapular rash with scaling is visible on the left palm.
A rash with this appearance typical for secondary syphilis.

Source: © IMPP

**Viral exanthema**
Photograph of the back of a young child:
This child shows a generalized, macular, pale, and fine-spotted rash. In this case, the child presented with signs and symptoms of a cold. The physical findings together with the history indicate the presence of a nonspecific virus exanthema, most commonly triggered by enteroviruses.

© AMBOSS

**Drug eruption (1/2)**
Ventral upper body of a patient presenting with a pruritic rash following the administration of amoxicillin
A diffuse rash composed of several fine erythematous papules is visible. This rash, known as a morbilliform rash because it resembles the rash seen in measles, is typical of a drug reaction.

© AMBOSS

**Drug eruption (2/2)**
Dorsal upper body of a patient presenting with a pruritic rash following the administration of amoxicillin
A diffuse rash composed of several fine erythematous papules is visible. This rash, known as a morbilliform rash because it resembles the rash seen in measles, is typical of a drug reaction.

© AMBOSS

**Scabies skin lesions**
Multiple erythematous papules (partially excoriated) are visible in the interdigital folds and on the dorsal aspect of the hand and fingers.

© AMBOSS

**Scabies**
Multiple papules with excoriation are visible on this patient's trunk, esp around the umbilicus, around which the skin appears lichenified.
These findings together with pruritus are suggestive of scabies.

© AMBOSS

**Atopic dermatitis**
Erythema and excoriations on the wrist of the left hand.

Source: © IMPP

Vesiculobullous rashes

Vesiculobullous rashes are composed of multiple fluid-filled lesions caused by a disorder of the epidermal-dermal junction.

Common causes of vesiculobullous rashes [2][4]
	Images	Distinguishing features	Diagnostic findings	Management
Varicella		Prodrome of fever, malaise, pharyngitis Macules, papules, and vesicles, simultaneously Spares hands and feet	Clinical diagnosis Positive PCR	Antihistamines Antiviral therapy for VZV infection (only for patients at high risk) See “Treatment for chickenpox.”
Shingles		Grouped vesicles with a dermatomal distribution Severely painful Most common in adults 50–70 years of age	Clinical diagnosis Positive PCR	Respiratory and contact isolation Early and mild: oral antiviral therapy for herpes zoster Severe: IV acyclovir See “Management of shingles.”
Necrotizing fasciitis [19]		Fever Patient appears severely ill Erythema of underlying skin Pain out of proportion to findings	Diagnostic findings of sepsis Positive tissue and fluid cultures	Emergent surgical debridement Empiric antibiotic therapy for skin and soft tissue infections See “Treatment” in “Necrotizing soft tissue infections.”
Hand, foot, and mouth disease [20]		Fever Malaise and anorexia Rash primarily on the hands and feet Painful oral ulcers	Clinical diagnosis	Supportive care for symptom relief
Bullous pemphigoid [21][22]		Diffuse large and tense vesicles Pruritic Prodrome of papular or urticarial lesions Negative Nikolsky sign	Positive serology, immunofluorescence assay, and/or histopathology	Mild: topical corticosteroids Severe: systemic corticosteroids See “Bullous pemphigoid.”
Pemphigus vulgaris [21][22]		Small flaccid and superficial bullae Ruptured bullae coalesce into large erosions. Oral lesions are common. Painful but not pruritic Positive Nikolsky sign	Positive serology, immunofluorescence assay, and/or histopathology	IV fluid resuscitation Wound care similar to burn management Systemic corticosteroids See “Pemphigus vulgaris.”
Bullous impetigo		Large thin-walled bullae Thin serous crust after rupture Most commonly affects the trunk and extremities Negative Nikolsky sign	Clinical diagnosis	Antibiotic therapy See “Management of impetigo.”
Contact dermatitis		History of exposure to a possible offending agent Distinct rash borders Pruritic	Clinical diagnosis Patch testing (if the diagnosis is uncertain)	Mild: topical corticosteroids Severe: systemic corticosteroids See “Contact dermatitis” for details.

See also “Autoimmune blistering diseases” and “Skin and soft tissue infections.”

Disseminated gonococcal infection, acute generalized exanthematous pustulosis, and smallpox may have a vesiculobullous appearance.

**Shingles**
Asymmetrical, red, vesicular lesion in the area of the right scapula, indicating reactivation of varicella-zoster virus (VZV).

Source: © IMPP

**Necrotizing fasciitis**
Posterolateral aspect of the left thigh, gluteal region, and popliteal fossa
There is significant diffuse edema and erythema across the entire visible region, with well-defined areas of necrosis, desquamation, and hemorrhagic bullae.
These features are strongly suggestive of necrotizing fasciitis, a rapidly progressive infection of the skin, subcutaneous tissue, and superficial and deep fascia that requires urgent debridement.

Source: “Figure 1, in: Late diagnosed necrotizing fasciitis as a cause of multiorgan dysfunction syndrome: A case report” by Smuszkiewicz P, Trojanowska I, Tomczak H, BMC Cases Journal, licensed under CC BY 2.0.

**Hand foot and mouth disease**
Source: “Hand foot and mouth disease” by Gzzz, Wikimedia Commons, licensed under CC BY-SA 4.0.

**Bullous pemphigoid**
Multiforme lesions and serous fluid-filled blisters of various sizes are visible over the entire anterior aspect of the patient's body. Marked erythema is also present.
These findings are consistent with bullous pemphigoid.

Source: © IMPP

**Pemphigus vulgaris**
Multiple ruptured blisters with surrounding erythema are visible. A single intact blister can be seen in the center of the image.
This finding is suggestive of pemphigus vulgaris, but histopathology is required to confirm the diagnosis.

Source: Courtesy of Dr. Gary M. White, MD

**Bullous impetigo**
Multiple vesicles, some of which have already ruptured and formed brown crusts, are visible on the gluteal region of this infant. The lesions in bullous impetigo are easily confused with the polymorphic rash of secondary syphilis.

Source: "ID#: 5154", CDC, Centers for Disease Control and Prevention licensed under Public Domain

**Allergic contact dermatitis**
Upper body of a man presenting with a severely pruritic rash after getting a henna tattoo on the right arm
An erythematous papulovesicular rash is visible over the chest and arms. The rash is most severe around the henna tattoo, which appears markedly erythematous.
This is the typical appearance of allergic contact dermatitis.

Source: © IMPP

Annular skin lesions

Overview of annular skin lesions
	Images	Etiology	Location	Characteristics
Erythema migrans		Early localized Lyme disease (Borrelia burgdorferi)	At the site of the tick bite	Slowly expanding red ring around the tick bite with a central clearing Painless Pruritic (rarely) Self-resolving within 3–4 weeks
Tinea corporis		Dermatophyte infection (Trichophyton rubrum)	Face Arms and legs Trunk	Centrifugally expanding round erythematous plaques with a central clearing Raised border with scales Pruritic
Erythema marginatum		Acute rheumatic fever	Trunk and extremities Spares the face	Centrifugally expanding pink or light red rash with a well-defined outer border and a central clearing Painless Nonpruritic
Nummular dermatitis		Immunological hypersensitivity reaction due to xerosis and damage to the epidermal lipid barrier	Extremities	Well-demarcated coin-shaped lesions Severely pruritic Scabbing
Granuloma annulare		Idiopathic	Localized form (more common): especially palms and soles Generalized form (rare): involves trunk and extremities	Palpable ring-shaped plaques that can be red, pink, violet, or skin-colored with a firm border and central clearing Hypopigmented or hyperpigmented in darker skin tones Pruritic Self-resolving within 2 years
Urticaria		Cutaneous mast cell activation and degranulation due to: Infection Type I hypersensitivity reaction Pseudoallergic reaction	Generalized involvement of the skin	Raised, well-demarcated, erythematous plaques (wheals) Round, oval, or serpiginous Pruritic Transient (disappear within 24 hours)
Erythema multiforme (EM)		Type IV hypersensitivity reaction to: Infection (most common): e.g., HSV, Mycoplasma pneumonia, fungal Drugs: e.g., barbiturates, phenytoin, NSAIDs, beta-lactam antibiotics, sulfonamides Immunizations: e.g., diphtheria, tetanus, influenza, HBV	Symmetrical distribution Backs of hands and feet first May affect the entire body EM minor: no involvement of mucous membranes EM major: mucosal involvement (oral, ocular, genital ulcers)	Initially manifest as erythematous macules, then as papules and vesicles, and finally, as target lesions May be asymptomatic or manifest with pruritus and/or painful burning Self-resolving within a month
Fixed drug eruption		Hypersensitivity reaction to specific drugs (e.g., antibiotics, NSAIDs, acetaminophen, barbiturates, anticonvulsants)	Most commonly involves oral mucosa, trunk, hands, and/or genitals Recurs in the same location on reexposure to the drug	Well-defined, round or oval, erythematous lesion that is usually solitary May develop vesicles or blisters Pruritic and/or burning
Pityriasis rosea		Idiopathic Viral (HHV 6 and 7)	Herald patch: typically on the trunk Secondary eruption: trunk and extremities	Herald patch (a few days to a few weeks before generalized rash) Secondary eruption Oval, salmon-colored papules and plaques Scaly collarette Christmas tree appearance (oriented along Langer lines) Both may be pruritic Self-resolving within 6–12 weeks
Discoid lupus		Genetic predisposition: HLA-DR2 and HLA-DR3 Hormonal factors (hyperestrogenic states) Environmental factors (e.g., tobacco smoking, UV light exposure)	Head Face Neck	Well-defined, erythematous scaly plaques Evolve into atrophic, disfiguring scars

**Erythema migrans in stage-I Lyme disease**
A large, primary lesion with circular erythema and central clearing on the posterior side of the right upper arm is visible.
This clinical picture is typical of erythema migrans (stage-I Lyme disease).
Illustration: Bull's eye sign

Source: "ID#: 9875", CDC/ James Gathany, Centers for Disease Control and Prevention (CDC) licensed under Public Domain

**Erythema migrans**
A round, homogeneous area of erythema with a diameter of approx. 14 cm can be seen on the right shoulder of this patient diagnosed with Lyme disease.
The circular expanding lesion forming around a tick bite is highly suggestive of erythema migrans, which is characteristic of Lyme disease.

Source: "ID#: 14482", Centers for Disease Control and Prevention licensed under Public Domain

**Tinea corporis (ringworm)**
Four round, erythematous plaques with central clearing and raised, scaly borders are visible on this patient's arm.

Source: © IMPP

**Erythema marginatum**
Left upper arm of a child diagnosed with acute rheumatic fever (ARF)
Erythematous plaques with areas of central clearing are visible on the ventral aspect of the forearm.
This is characteristic of erythema marginatum, the characteristic annular erythema occuring in 10% of attacks of acute rheumatic fever in children, caused by group A streptococcus.

Source: “Erythema marginatum” by Adsie, Wikimedia Commons, licensed under CC BY-SA 4.0. Modifications: image has been cropped.

**Nummular eczema**
Upper ankle region with a round, red-brown, scaly plaque.
Nummular eczema is usually associated with severe pruritus. Tinea corporis should be considered as a differential diagnosis.

Source: Courtesy of Dr. Gary M. White, MD

**Granuloma annulare**
Photograph of the dorsum of the hand
Ring-shaped lesions are visible over the 2^nd and 4^th knuckles.
On closer inspection, each ring is composed of multiple non-scaly mildly erythematous papules and nodules, some of which are skin-colored.
Each lesion has a central clearing.
These non-scaly annular lesions are characteristic of granuloma annulare, an idiopathic, benign, non-contagious cutaneous lesion.

Source: © IMPP

**Localized granuloma annulare**
Hypopigmented, nonscaly papules are visible on the patient's chin. The lesions coalesce to form arciform or annular patterns.
These lesions are characteristic of granuloma annulare. The absence of scaling distinguishes this feature from tinea corporis.

Source: “Figure 16, in: Clinical Manifestations of Sarcoidosis and Granulomatous Disorders” by Suchibrata Das, IntechOpen, licensed under CC BY 3.0.

**Target lesions in erythema multiforme**
Multiple well-defined lesions can be seen on the back of the hand. The lesions consist of concentric rings with an outer erythematous zone, a paler intermediate zone, and a darker violaceous center, consistent with target lesions. Some of the lesions show central blistering.
This presentation is typical of erythema multiforme.

Source: © IMPP

**Erythema multiforme**
Multiple circular lesions with a central papule and raised edges (also called “target lesions”), surrounded by a lighter edematous area, are visible on the anterior aspect of the thighs.
This is the typical appearance of erythema multiforme.

Source: Courtesy of Dr. Gary M. White, MD

**Fixed drug eruption**
Multiple, heterogeneous, and mostly bullous lesions with characteristic, slight erythematous rims around a hyperpigmented center are visible.
While blisters and/or ulcerations of the damaged skin may not always occur, the rest of the highlighted findings are still suspicious for a fixed drug eruption.

Source: “Figure 94 c: Classic round pigmented {...}; in: Atlas of Pediatric HIV Infection” by Regina E. Oladokun; Rannakoe J. Lehloenya; Carol Hlela et al., Openbooks, licensed under CC BY-ND 4.0.

**Pityriasis rosea**
A secondary rash after primary plaque formation (not shown) can be seen on the back of this patient. The secondary eruption of pityriasis rosea is usually episodic and distributed along Langer lines.

Source: © IMPP

**Herald patch (mother patch) in pityriasis rosea**
The primary plaque (located on the trunk) in this image is the initial and largest lesion in pityriasis rosea. The surface shows irregular scaling.

Source: "ID#: 5506", CDC/ Dr. Sellars, Centers for Disease Control and Prevention (CDC) licensed under Public Domain

**Discoid lupus erythematosus**
Multiple annular (discoid), sharply demarcated, erythematous plaques, 0.5–3 cm in diameter with central atrophy and scaling are visible underneath the right ear. Additional scaly plaques are located on the lobe, helix, and antihelix of the ear.
These are the characteristic features of discoid lupus erythematosus (DLE), a chronic, scarring variant of cutaneous lupus erythematosus. DLE lesions are typically pruritic and have a propensity to first appear on the face and neck.

Source: © IMPP

**Discoid systemic lupus erythematosus**
Back of a patient with Takayasu arteritis
Several annular (discoid), sharply-demarcated, erythematous lesions can be seen. The center of the lesions appears atrophic.
These are characteristic features of discoid systemic lupus erythematosus.

Source: “Figure 1, in: Takayasu’s Arteritis with Systemic Lupus Erythematosus: A Rare Association” by Dhrubajyoti Bandyopadhyay, Vijayan Ganesan, Debarati Bhar, Diptak Bhowmick, Sibnarayan Sasmal, Cankatika Choudhury, Sabyasachi Mukhopadhyay, Adrija Hajra, Manas Layek, Partha Sarathi Karmakar, Hindawi, licensed under CC BY 3.0.

Mimics

Skin nodules [23][24]

A skin nodule is an elevated cystic or solid lesion > 1 cm in diameter.

Sebaceous hyperplasia
Epidermal inclusion cysts
Dermatofibroma
Acrochordon
Rheumatoid nodules
Nonmelanoma skin cancer
Chancre
Leprosy

Rheumatoid cutaneous nodules

Cutaneous ulcers [25]

Cutaneous ulcers are rounded or irregularly shaped discontinuities in the skin caused by loss of the epidermis and some portion of the dermis.

Chronic venous disease
Peripheral artery disease
Collagen vascular disease
Vasculitides
Pyoderma gangrenosum
Necrobiosis lipoidica
Decubitus ulcer

Advanced chronic venous insufficiency

**Rheumatoid cutaneous nodules**
A nodule is visible in the palm of this patient's hand.
This appearance is typical of rheumatoid nodules in rheumatoid arthritis.

Created by: Dr. Thomas Rath, Münster. Modifications to original image: Image slightly lightened.

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