Diagnosis: Guttate psoriasis
We diagnosed guttate psoriasis in this patient based on her history and physical exam, a throat culture that was positive for group A beta-hemolytic streptococci, and blood work that showed an elevated antistreptolysin O titer. Further confirmation was obtained via punch biopsy.
Guttate psoriasis is a fairly uncommon form of psoriasis, affecting approximately 2% of patients with psoriasis.1 It is characterized by the abrupt onset of pruritic, salmon-pink 1- to 10-mm drop-like lesions with fine scale that may spread to the face, but spare the palms and soles. It’s uncommon for this sub-type of psoriasis to involve the nails.
Guttate psoriasis affects individuals younger than 30 years of age; there appears to be no gender predilection.2 The rash usually appears 2 to 3 weeks after an upper respiratory group A beta-hemolytic streptococci infection. Although less common, there have also been reports of guttate psoriasis associated with perianal streptococcal disease.2
While the pathophysiology is unclear, recent evidence suggests that a genetic autoimmune-mediated reaction to a recent streptococcal infection in immunologically susceptible hosts is at work. It’s thought that T-cell stimulation from a streptococcal superantigen is responsible for the acute cutaneous eruption. Various human leukocyte antigens, including HLA-Bw17, HLA-B13, and HLA-Cw6, have been identified and appear to confer a genetic predisposition to the development of guttate psoriasis.3