Atrophying pityriasis versicolor as an idiosyncratic T cell-mediated response to Malassezia: A case series.

BACKGROUND: Atrophying pityriasis versicolor (PV), first described in 1971, is a rare variant in which lesions appear atrophic. OBJECTIVE: We sought to determine the pathophysiology of atrophying PV. METHODS: A retrospective chart review identified 6 cases of atrophying PV. In all cases, routine light microscopy, an elastic tissue stain, and immunohistochemical assessment for the expression of CD3, CD4, CD8, GATA3 and CXCR3 was performed. RESULTS: All cases demonstrated hyperkeratosis with intracorneal infiltration by pathogenic hyphal forms as well as epidermal attenuation and papillary dermal elastolysis. A supervening, mild-to-moderate, superficial lymphocytic infiltrate was noted and characterized by a focal CD8[+] T cell-mediated interface dermatitis along with a mixed T-cell infiltrate composed of GATA3[+] and CXCR3[+] T cells. LIMITATIONS: Small sample size and the loss of some patients to follow-up. CONCLUSION: Atrophying PV represents the sequelae of a mixed helper T-cell (TH1 and TH2) idiosyncratic immune response to Malassezia and can present as a protracted dermatosis that may clinically mimic an atypical lymphocytic infiltrate. TH1 cytokines can recruit histiocytes, a source of elastases, and upregulate matrix metalloproteinase activity, which may contribute to epidermal atrophy.