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Rash with Fever: Differential Diagnosis & Urgency Assessment

Fever + rash = broad differential; pattern recognition guides urgency.

Emergent (Hours Matter)

Meningococcemia: Petechial/purpuric rash, hypotension, altered mental status → EMERGENCY
Toxic Shock Syndrome: Diffuse erythroderma, desquamation, multi-organ failure
Rocky Mountain Spotted Fever: Centrifugal petechial rash (wrists/ankles → trunk), tick exposure
Kawasaki Disease: Fever ≥5d + polymorphous rash, conjunctivitis, oral changes, extremity changes, lymphadenopathy

Common Infectious Exanthems

Non-Infectious

Drug eruption (morbilliform, DRESS, SJS/TEN)
Autoimmune (SLE malar, vasculitis palpable purpura)
Kawasaki (above)

Action Plan

Assess ABCs, hemodynamics
Blanchable vs. non-blanchable (petechiae/purpura = urgent)
Mucosal involvement? (SJS/TEN, Kawasaki)
Travel, contacts, medications, immunization status
Labs: CBC, CRP, cultures, serologies, biopsy if needed

Non-blanching rash + fever = medical emergency until proven otherwise.

Skin Conditions - Related Articles

Disease	Rash Pattern	Key Features
Measles	Maculopapular, cephalocaudal, confluent	Koplik spots, 3 Cs, high fever
Varicella	Vesicles on erythematous base (dew drops), crops	Centripetal, pruritic, all stages
Rubella	Fine pink, face → trunk, fades fast	Postauricular lymphadenopathy
Scarlet Fever	Sandpaper, circumoral pallor, strawberry tongue	GAS pharyngitis, Pastia's lines
Roseola	Rose-pink, trunk → extremities, AFTER fever breaks	High fever 3–5d, then rash
Enteroviruses	Varied (HFMD, herpangina, Boston exanthem)	Summer/fall, mild systemic