Equestrian chilblain: another outdoor recreational hazard.

Herein, we describe two cases and review 14 cases of equestrian chilblain or 'equestrian cold panniculitis' in the literature. The first, a 23-year-old healthy female horse trainer, presented with burning nodular swelling on her lateral thighs. The second was a 34-year-old healthy woman with recurrent nodular eruption on the lateral thighs after horseback riding in the winter. Physical examination of both patients revealed erythematous to violaceous nodules with eczema craquelé-like changes. Laboratory workup for systemic and autoimmune connective tissue disease was negative. Punch biopsies from both patients showed a superficial and deep perivascular and periadnexal lymphocytic infiltrate with focal extension into the subcutaneous fat. Parakeratosis, subtle spongiosis and increased pandermal interstitial mucin were also present. Previously reported cases generally showed a similar clinical course and similar histopathologic findings. In contrast, our cases revealed increased pandermal interstitial mucin, resembling tumid lupus erythematosus. We aim to better characterize the histopathologic findings of equestrian chilblain and discuss its relationship to other cold-induced skin injuries and autoimmune connective tissue disease, namely lupus erythematosus.