Rapid-onset rash in child
Our patient’s pruritic rash was spreading throughout his trunk and arms. An acute infection 10 days earlier shed light on the diagnosis.
Diagnosis: Guttate psoriasis
A diagnosis of guttate psoriasis was made based on the physical exam findings and the preceding group A beta-hemolytic streptococcal infection.
This condition affects approximately 2% of all patients with psoriasis; it is characterized by the acute onset of multiple erythematosquamous papules and small plaques that look like droplets (“gutta”).1 It tends to affect children and young adults and typically occurs following an acute infection (eg, streptococcal pharyngitis).2,3 In this case, a rapid strep test and throat culture positive for group A Streptococcus supported the diagnosis.
Although this particular phenotype of psoriasis is usually associated with streptococcal infection and mainly occurs in patients with the HLA-Cw6+ allele, the specific immunologic response that causes these skin lesions is poorly understood.4 Antigenic similarities between streptococcal proteins and keratinocyte antigens might explain why the condition is triggered by streptococcal infections.5
Pityriasis rosea and tinea corporis are part of the differential
The differential includes skin conditions such as pityriasis rosea, tinea corporis, varicella, and insect bites.
Pityriasis rosea can manifest as a papulosquamous eruption, but it has an inward-facing scale, called a collarette. The “Christmas tree” pattern on the back that is preceded by a solitary 2- to 10-cm oval, pink, scaly herald patch (in 17%-50% of cases) is key to the diagnosis.6 (For more information, see “Rash on trunk and upper arms.”)
Continue to: Tinea corporis...
