Understanding Guttate Psoriasis

Guttate psoriasis refers to a distinctive, acute clinical presentation of an eruption characterized by small, droplike, 1-10 mm in diameter, salmon-pink papules, usually with a fine scale. The word guttate comes from the Latin word gutta, meaning drop. This type of psoriasis primarily occurs on the trunk and the proximal extremities, but it may have a generalized distribution.
It is most common in individuals younger than 30 years with a history of upper respiratory infection secondary to group A beta-hemolytic streptococci (eg, Streptococcus pyogenes) often precedes the eruption by 2-3 weeks. Although recurrent episodes may occur, especially those due to pharyngeal carriage of streptococci, isolated bouts are known to occur.
The sudden appearance of the papular lesions may be either the first manifestation of psoriasis in a previously unaffected individual or an acute exacerbation of long-standing plaque psoriasis. On the other hand, guttate psoriasis may be chronic and unrelated to a streptococcal infection.
The exact pathophysiologic mechanism is undetermined. The disease is believed to result from an immune reaction triggered by a previous streptococcal infection. T lymphocytes and cytokines are believed to cause the characteristic inflammatory changes appreciated on histopathologic examination of lesional skin samples. An autoimmune phenomenon has also been postulated because some streptococcal products and components have been found to cross-react with normal human epidermis. Electron microscopic studies have shown that mast cell degranulation is an early and constant feature in the evolution of guttate psoriatic lesions.