A Young Male with a Rash of Scales

11-year-old Mike is brought in for a scaly rash that started several days ago. He had a sore throat last week and was treated for “Strep throat” based on a rapid strep test and confirmed by a positive culture. He has not had any skin problems in the past other than dandruff.

The family history and Mike’s past medical history are non- contributory. His main concern is this unsightly, but asymptomatic rash.

A closer look shows the tear-drop shaped scales are symmetrical on his trunk and proximal extremities.

A closer look shows the tear-drop shaped scales are symmetrical on his trunk and proximal extremities.

On closer inspection, we see that the rash consists of 0.5mm-1mm ovoid-to-slightly-round papulosquamous lesions with a silvery scale. The scale is quite adherent and attempts to scrape the lesions result in punctate bleeding.

We have an adherent silvery scale; we have an antecedent upper respiratory infection with documented group A Streptococcus. Could it be: Seborrheic dermatitis Onychomycosis Squamous cell carcinoma Nummular eczema Lichen planus Lichen simplex chronicus Mycosis fungoides? Or, perhaps, this is a near perfect story for a diagnosis other than one listed above.

Answer: Guttate psoriasis. Most often occurs in children and young adults (less than 30 years of age).The silvery scale with punctate bleeding (Auspitz sign) is a tip off. Remember there is a spectrum of disease for psoriasis, so guttate psoriasis is not predictive of extensive disease.

Most often seen in persons younger than 30 years of age. Preceding strep infections (including perianal strep) are reported commonly. Viral infections can trigger the rash. It is thought that specific streptococcal proliferative factor effects the keratinocytes…the Koebner phenomenon - an isomorphic response to trauma? Rash follows within 2 to 3 weeks of infection. May be first appearance of psoriasis in a previously unaffected person or exacerbation of existing disease.

Triggers to consider: Upper respiratory infections. Streptococcal infections other than tonsillitis. Stress injury to the skin. Certain drugs (eg, antimalarials, ß-blockers). Guttate psoriasis often comes on quite suddenly. More common (including recurrence) in patients with weakened immunity: Autoimmune disorders (including rheumatoid arthritis), AIDS, chemotherapy for cancer

Treatment: Topicals are the preferred treatment for guttate psoriasis (eg, steroid cream,vitamin D and coal tar applications) Patients often find it tedious to apply to multiple small lesions. If topical treatment fails, refer to dermatologist for phototherapy. Phototherapy with ultraviolet light B (UVB) or PUVA (psoralen/ultraviolet light A) has proven very effective. Systemic agents are prescribed only rarely and in severe cases. A short course of a systemic agent may lead to rapid and prolonged clearing.