Panniculitis is an inflammation of the layer of subcutaneous fat underlying the epidermis of the skin. Acute panniculitis is also called nodular fat necrosis.
Panniculitis may result from a variety of conditions. While it is not possible to develop a firm classification of acute panniculitis, one may distinguish between panniculitis without systemic (throughout the body) disease and panniculitis with systemic disease.
Panniculitis without systemic disease is usually due to trauma or a cold. One variant, subcutaneous fat necrosis of the newborn, may be due to a combination of obstetric trauma and hypothermia (low body temperature).
Panniculitis with systemic disease includes collagen vascular disease (lupus and scleroderma), lymphoma, pancreatic cancer and pancreatitis.
The appearance of single or multiple crops of nodules in subcutaneous fat is the hallmark of acute panniculitis. The nodules are usually, but not always, tender. On occasion, they drain an oily solution and suppuration (pus) may occur. Individual lesions last from one to eight weeks before disappearing, and a pigmented depressed area may be left at the involved site.
While some patients have only nodular panniculitis, which may or may not be relapsing, others may develop fever, abnormal liver function, involvement of the bone marrow, bleeding tendencies, nodular pulmonary lesions and evidence of pancreatic disease. This constellation of findings has been called Weber-Christian disease.
Acute panniculitis can be diagnosed only histologically, usually by biopsy of tissue. Once the lesion is identified, a search for the cause must be made. If systemic symptoms are present, the primary differential diagnosis is between collagen vascular disease, lympho-proliferative disorder and pancreatitis or pancreatic cancer.
Treatment is often unsatisfactory. Some physicians may use anti-inflammatory medications. Some patients with certain types of panniculitis may respond to combined chemotherapy with cyclophosphamide, bleomycin and prednisone.