Panniculitis. Part 11. Mostly lobular panniculitis

The second part of our review of panniculitis summarizes the clinicopatholo gic features of the mostly lobular panniculitides. Erythema induratum of Ba zin (nodular vasculitis) represents the most common variant of lobular pann iculitis with vasculitis, although controversy persists about the nature of the involved vessels. Mostly lobular panniculitides without vasculitis com prise a series of disparate disorders. These include sclerosing panniculiti s that results from chronic venous insufficiency of the lower extremities; panniculitis with calcification of the vessel walls such as calciphylaxis a nd oxalosis; and inflammatory diseases with crystals within the adipocytes such as sclerema neonatorum, subcutaneous fat necrosis of the newborn, and poststeroid panniculitis. Connective tissue diseases, such as systemic lupu s erythematosus and dermatomyositis, pancreatic diseases, and alpha (1)-a n titrypsin deficiency may also show a mostly lobular panniculitis with chara cteristic histopathologic features. Lobular panniculitis may also be an exp ression of infections, trauma, or factitial causes involving the subcutaneo us fat. Lipoatrophy refers to a loss of subcutaneous fat due to a previous inflammatory process involving the subcutis, and it may be the late-stage l esion of several types of panniculitis. In contrast, lipodystrophy means an absence of subcutaneous fat with no evidence of inflammation and often the process is associated with endocrinologic, metabolic, or autoimmune diseas es. Finally, cytophagic histiocytic panniculitis is the term that has been used to describe two different processes: one is inflammatory, a lobular pa nniculitis, and the other one is neoplastic, a subcutaneous T-cell lymphoma . The only common feature of these two different processes is the presence of cytophagocytosis in the lesions.