DISCUSSION
This child's rash was diagnosed as guttate psoriasis. Dermatophytosis and ringworm are different terms for the same disease, a superficial fungal infection that she might well have contracted from the kitten. But a negative KOH finding and nonresponse to topical antifungal cream means these diagnoses are unlikely. Nummular eczema could easily have been the correct diagnosis, but it is unlikely to manifest so rapidly, and with so many lesions.
Treatment The tendency to develop guttate psoriasis is primarily related to two factors: (1) a family history of psoriasis and (2) recent streptococcal infection (of whatever type) as an immunologic trigger in a genetically-susceptible patient. Guttate psoriasis tends to appear on children far more often than on adults and can be fairly itchy and florid, as in this case. Adults or children with pre-existing psoriasis vulgaris can present with new lesions manifesting in part with a guttate morphology along with their usual plaques, but the typical patient with guttate psoriasis only has the droplike lesions.
The worrisome part of guttate psoriasis is its tendency to progress into permanent psoriasis vulgaris, which happens in up to two-thirds of cases. Therefore, the standard of care has become prompt treatment with topical corticosteroid cream, such as triamcinolone 0.025%, for the itching and an oral antibiotic to eradicate any residual streptoccocal infection. Phototherapy with narrow-band UVB is often necessary, though it is somewhat impractical because it requires two to three office visits a week. The best thing primary care providers can do for these patients is to institute treatment but begin the referral process early on.
This condition is almost invariably misdiagnosed as "ringworm" by the nondermatology clinician, and certainly new kittens are a common source of a rather aggressive form of dermatophytosis caused by Microsporum canis. KOH testing is helpful in differentiating between this and psoriasis, but occasionally biopsy proves necessary. JAAPA
Joe Monroe practices at the Dawkins Dermatology Clinic, Oklahoma City, and is the department editor for Dermatology Digest. The author has indicated no relationships to disclose relating to the content of this article.