Acute infectious id panniculitis/panniculitic bacterid: a distinctive form of neutrophilic lobular panniculitis.

BACKGROUND: Lobular panniculitis encompasses lupus profundus, atypical lymphocytic lobular panniculitis, erythema induratum and subcutaneous Sweet's syndrome, while septal panniculitis includes erythema nodosum and fibrosing dermal processes of burn out necrobiosis lipoidica and morphea profundus. Panniculitis may represent a sign of systemic disease and/or a modified immune response to hematogenously disseminated antigen. METHODS: We describe 10 cases of sterile neutrophilic dominant lobular panniculitis that represented an id reaction to non-tuberculous stimuli. RESULTS: Four males and six females had sudden tender non-ulcerated lower extremity nodules with preceding non-tuberculous infectious triggers. Three also had upper extremity lesions. Biopsies showed dominant neutrophilic infiltrate with subcutaneous microabscesses (7), extravascular granulomatous infiltrates (5), thrombotic microangiopathy (5) and necrotizing vasculitis (5). Stains evaluating microbial pathogens were negative. Lesions resolved with antibiotic treatment and/or abscess drainage; no case recurred. Medical histories included atopic diathesis (4), primary antiphospholipid antibody syndrome (1), ulcerative colitis (1) and acute lymphocytic leukemia (1). Serologies showed polyclonal hypergammaglobulinemia, cold agglutinins and cryofibrinogens. CONCLUSIONS: We propose the term acute infectious id panniculitis for cases of neutrophilic lobular panniculitis triggered by non-tuberculous infectious stimuli. This course may be self-limited. Microvascular cofactors and/or procoagulant states may be pathogenetically important. Recognizing this entity may circumvent the need for an exhaustive evaluation for other causes of neutrophilic lobular panniculitis.