When the patient presents with a rash of two or more parts of the body with onset over days, the morphology is key. Is it urticarial? eczematous? Maculopapular? Pustular?
|Morphology||Typical Causes||Reference Page|
|Maculopapular||Drug Eruption, Measles|
|Papulosquamous||Guttate Psoriasis, Secondary Syphilis, Pityriasis Rosea||Papulosquamous|
|Pustular||Bacterial folliculitis, Hot Tub Folliculitis, Agep||Pustules Follicular, Non-follicular|
|Eczematous||Allergic Contact Dermatitis||Eczematous|
|Vesicular||Insect Bites , Chickenpox||Vesicles|
|Papular, Inflammatory||Insect Bites , Viral exanthem||Papules, Red, Acute|
|Mucous Membrane Inv.||Stevens Johnson Syndrome, TEN|
Viral exanthem--Small, diffuse inflammatory papules.
Drug eruption--Classic macuopapular. Good history of a new drug.
Urticaria The key question here is do the lesions move from location to location in less than 24 hours?--yes for urticaria.
Hypersensitivity Reaction--hives vs drug eruption. This 16 year old boy had just started minocycline. The urticarial reaction started within 2 hours of taking the first pill.
Stevens Johnson Syndrome
Erythema Multiforme True target lesions as shown here are uncommon.
Vasculitis Purpuric lesions imply a vasculitis.
Pityriasis rosea Note the herald patch on the left shoulder.
Secondary Syphilis Any involvement of the palms and soles should make one consider secondary syphilis.
The above, plus
Graft versus host disease
Lymphocyte recovery syndrome
Neutrophilic eccrine hidradenitis/chemotherapy induced eccrine squamous syringometaplasia