Blistering Rash
Rapid Review
- Differentials
- Febrile
- Varicella
- Hand-foot-and-mouth disease
- Necrotizing fasciitis
- Disseminated gonococcal disease
- Purpura fulminans
- Disseminated intravascular coagulopathy (DIC)
- Staph Scalded Skin Syndrome (SSSS)
- Toxic Epidermal Necrolysis (TEN)
- Afebrile
- Bullous pemphigoid
- Pemphigus vulgaris
- Contact dermatitis
- Herpes zoster
- Dyshidrotic eczema
- Burns
- Febrile
- History
- Recent new medications
- Rapid vs gradual onset
- Physical Exam
- Diffuse or localized
- Localized suggests contact dermatitis, herpes zoster, eczema, or coxsackie virus
- Abnormal Vitals (tachycardia, hypotension)
- Consider meningitis, DIC, endocarditis
- Palpable vs Non-palpable
- Non-palpable suggests thrombocytopenia or DIC
- Positive Nikolsky sign
- Consider pemphigus vulgaris, SSSS, TEN
- Diffuse or localized
- Work-up
- Labs
- CBC, BMP, blood/urine cultures
- Skin biopsy
- If suspect SJS/TEN
- PCR of DNA of vesicular fluid
- If suspect varicella-zoster
- Labs
Pearls
- Elderly patients presenting with a blistering rash should be considered for pemphigous vulgaris or bullous pemphigoid.
- Always be on the lookout for end-organ dysfunction in these patients, which may be suggestive of steven-johnson syndrome or toxic epidermal necrolysis.
Erythematous Rash
Rapid Review
- Differentials
- Positive Nikolsky sign
- Staph Scalded Skin Syndrome
- Toxic Epidermal Necrolysis
- Negative Nikolsky sign
- Drug reaction w/ eosinophilia and systemic symptoms (DRESS)
- Kawasaki
- Scarlet fever
- Anaphylaxis
- Angioedema
- Scombroid
- Positive Nikolsky sign
- History
- Fever/chills
- Recent new food/drug exposure
- History of allergies
- Physical Exam
- Nikolsky sign
- Narrows differential (see above)
- Mucosal involvement
- Consider angioedema, Kawasaki
- Nikolsky sign
- Work-up
- CBC, BMP,
- Skin biopsy
- If suspect EM/SJS/TEN
Pearls
- Be wary of the “false Nikolsky sign”, which is elicited by pulling the peripheral remnants of a blister that has already ruptured. This commonly occurs in bullous pemphigoid and is not representative of a true positive Nikolsky sign.
- Always consider infectious etiologies (ex.cellulitis, MRSA, SSSS) inpatients presenting with diffuse erythematous rashes.
Maculopapular Rash
Rapid Review
- Differentials
- Central distribution
- Viral exanthem
- Lyme disease
- Drug reaction
- Pityriasis
- Peripheral distribution
- Steven Johnson Syndrome (SJS)
- Erythema multiforme
- Meningococcemia
- Rocky mountain spotted fever
- Syphilis
- Lyme disease
- Scabies
- Eczema
- Psoriasis
- Central distribution
- History
- Fever/chills
- Outdoor exposures
- Recent viral infection
- Recent new medication
- Physical Exam
- Central vs Peripheral
- Narrow differentials
- Targetoid
- Suggests erythema multiforme or lyme disease
- Scaling
- Consider scabies, tinea, psoriasis
- Central vs Peripheral
- Work-up
- CBC, BMP,
- Skin biopsy
- If suspect EM/SJS/TEN
- Serologic testing for Lyme
Pearls
- Most cases of maculopapular rashes can be diagnosed with a careful history and physical exam.
- Maculopapular drug eruptions often occur between 4 and 21 days of initiation of the medication.
Deep Dive
Petechial Rash
Rapid Review
- Differentials
- Febrile
- Meningococcemia
- Disseminated gonococcal infection
- Henoch-Schlonein purpura
- Rocky mountain spotted fever
- Endocarditis
- Disseminated intravascular coagulopathy (DIC)
- Thrombotic Thrombocytopenic Purpura (TTP)
- Hemolytic Uremic Syndrome (HUS)
- Afebrile
- Autoimmune vasculitis
- Idiopathic thrombocytopenic purpura (ITP)
- Febrile
- History
- Fever
- Food exposure
- Recent vaccines
- Chronic illness
- Physical Exam
- Abnormal Vitals (tachycardia, hypotension)
- Consider meningitis, DIC, endocarditis
- Palpable vs Non-palpable
- Non-palpable suggests thrombocytopenia or DIC
- Abnormal Vitals (tachycardia, hypotension)
- Work-up
- Labs
- CBC, Coagulation studies, D-dimer, fibrinogen level, CMP, blood cultures (if febrile/toxic)
- Labs
Pearls
- Facial petechiae is often benign and doesn’t necessitate a work-up unless history is concerning for assault/non-accidental trauma.
- Any fever associated with a petechial rash warrants an extensive work-up and evaluation.
Deep Dive
Emergency Medicine Physician Assistant. Duke University Graduate. Army National Guard PA/Combat Medic. Former Paramedic. Devoted to learning and sharing evidence-based medicine.