Idiopathic perniosis and its mimics: a clinical and histological study of 38 cases.

Perniosis is a term applied to cold-induced painful or pruritic erythematous or violaceous acral papular or nodular lesions. We examined 39 skin biopsies from 38 patients who presented with acral purpuric lesions, suggesting a diagnosis of perniosis clinically or pathologically. The presence of a systemic or extracutaneous disease was established in 17 patients, including 5 with systemic lupus erythematosus (SLE), 3 with antiphospholipid antibodies, in 1 in whom there was underlying HIV disease, 2 with viral hepatitis, 2 with rheumatoid arthritis (RA), 2 with cryofibrinogenemia, 1 with hypergammaglobulinemia, 1 with iritis, and 1 with Crohn's disease. In the other 21 patients, the clinical presentations prompted further studies in 12, which showed a positive antinuclear antibody (ANA) in 10. A diagnosis of idiopathic perniosis (IP) was rendered in all 21 of these patients including those in whom a positive ANA was discovered, based on the absence of any other serological markers, signs, or symptoms indicative of a specific systemic disease complex; many had Raynaud's phenomenon, small joint arthralgias, atopy, or a family history of either connective tissue disease or Raynaud's disease. The histopathology of IP comprised a superficial and deep angiocentric lymphocytic infiltrate with papillary dermal edema and lymphocytic exocytosis directed to retia and acrosyringia. A few cases showed a mild vacuolopathic or lichenoid interface dermatitis, adventitial dermal mucinosis, lymphocytic eccrine hidradenitis, vascular ectasia, and thrombosis confined to dermal papillae capillaries. The biopsies from patients with iritis, RA, and Crohn's disease showed a granulomatous vasculitis and a granuloma annulare-like tissue reaction. The biopsies from the patients with SLE, cryofibrinogenemia, primary antiphospholipid antibody syndrome, and hypergammaglobulinemia shared a similar histopathology comprising an interface dermatitis, superficial and deep angiocentric and eccrinotropic lymphocytic infiltrates, vascular ectasia, and dermal mucinosis with prominent involvement of the eccrine coil. Many cases did not show features of IP, namely papillary dermal edema, thrombosis of dermal papillary capillaries, and lymphocytic exocytosis into the retia and acrosyringia. There was frequent vascular fibrin deposition involving reticular dermal vessels. The latter two variables were statistically significant discriminators between IP and in perniotic lesions observed in the setting of underlying systemic disease. With respect to the latter, some cases occurred in the setting of cold exposure and were designated by us as "secondary perniosis" (SP), whereas others showed no specific association with cold exposure and were designated as perniotic mimics (PMs) based exclusively on the gross and microscopic morphology of the lesions.