Rash Decisions

December 31, 2006

This 2 1/2-year-old boypresents for evaluation ofan asymptomatic, nonpruritic,nonblanchable rashthat is primarily confined tohis cheeks. There is someerythema on the extensorsurfaces of the proximalextremities. The motherreports that the child hadan upper respiratory illnessabout 3 days earlier, withcough and a slight fever.He took no medication forthat illness. Because thesymptoms were so mild,she had not brought thechild in for medical attention.The rash appearedafter the fever and coughresolved. The child isotherwise healthy and hetakes no medication.

Your patient's rashlooks like this . . .This 2 1/2-year-old boypresents for evaluation ofan asymptomatic, nonpruritic,nonblanchable rashthat is primarily confined tohis cheeks. There is someerythema on the extensorsurfaces of the proximalextremities. The motherreports that the child hadan upper respiratory illnessabout 3 days earlier, withcough and a slight fever.He took no medication forthat illness. Because thesymptoms were so mild,she had not brought thechild in for medical attention.The rash appearedafter the fever and coughresolved. The child isotherwise healthy and hetakes no medication.Which of thefollowing morphologiccategories does thispatient's rash mostclosely resemble?MACULES
Discolored lesions not elevatedabove or depressedbelow skin surfacePAPULES
Raised bumps PUSTULES
Blisters of variable sizefilled with pus, and thereforecloudyVESICULOBULLOUS
Small, circumscribedepidermal elevations DERMATOMAL ORLINEAR LESIONS
Grouped, flat red lesionsassociated with unilateraldermatomal distributionPLAQUE
Broad elevation, shapedlike a plateau; frequentlyformed by confluence ofpapulesThis rash ismacular.The lesion is neitherelevated nor depressedrelative to the surroundinguninvolved skin. Thus, thispatient's rash is macular.Which picture below most closely matches the general color of the patient's rash?HYP0PIGMENTED MACULEERYTHEMATOUS MACULEHYPERPIGMENTED MACULEBLUE MACULEThe child in this case has an erythematous macular rash. The Table below displays the most likely causes of erythematousmacules in children.Match the features of this patient's rash with specific characteristics listed. Use the checkboxes to mark off theclosest diagnostic contenders.The child in this case history has aviral exanthem. This is Fifth disease, caused byparvovirus B19. The confluent lesions thattypically develop on the face may make thechild look like he or she has been slapped. Theeruption (which may or may not be pruritic) inthis self-limited condition may wax and wanefor several weeks.The 6 conditionspictured are theprimary differentialdiagnosticconsiderations.Atopic dermatitis canaffect the cheeks in children;however, the diagnosiswas ruled out in thiscase for several reasons.Atopic rashes are usuallyapparent in the first year oflife; also, one would expectmore scale and, possibly,more pruritus--especiallyon the extremities. Also,the absence of flexuralinvolvement of the extremitiesargues against thisdiagnosis.Drug reaction is a possibility,except that this childhas no history to supportthis diagnosis.Seborrhea usually affectsthe paranasal areas, eyelidand eyebrow regions; itdoes not commonly occuron the face of youngchildren.Candida infections areusually more inflammatory,more scaly, and bettercircumscribed than a viralexanthem.Contact dermatitis is adiagnostic possibility, butone would expect morescale and pruritus.Nummular eczema hasa ringed appearance; itsmorphology rules it out asa diagnostic contender inthis case.