Cold-Associated Perniosis of the Thighs ("Equestrian-Type" Chilblain): A Reappraisal Based on a Clinicopathologic and Immunohistochemical Study of 6 Cases.

Cold-associated perniosis of the thighs ("equestrian cold panniculitis") is an unusual and still enigmatic entity. The authors retrieved 6 cases for a re-evaluation of their clinicopathologic features and for an immunohistochemical assessment with antibodies anti-CD3, anti-CD20, and anti-CD123. All patients were women, aged 17-45 years. One of them had elevated antinuclear antibody titers. Available anamnestic data confirmed the triggering role of prolonged/intermittent exposure to cold (not necessarily for equestrian activities). The lesions affected the thighs, with a preferential, although not exclusive involvement of the upper lateral surface. The histopathological pattern was perivascular, superficial, and deep, extending toward the superficial fat lobules, with lymphocytic vasculitis and mucin deposition; clumps of CD123 cells were found in 4 of 6 cases. Cold-associated perniosis of the thighs cannot be considered as a panniculitis. The histopathological features considerably overlap with perniosis at other sites of the body and with chilblain lupus erythematosus.