The condition presents as tender, red, erythematous subcutaneous nodules, most frequently on the lower extremities, although they may occur on the breasts, upper extremities, trunk, and buttocks. Long-standing subcutaneous nodules often ulcerate spontaneously and drain a yellow to brown oily material. Given the propensity for this panniculitis to ulcerate, cases have often been misdiagnosed as an infectious process such as necrotizing fasciitis and have thus undergone unnecessary surgical debridement. The distal lower extremities, notably around the ankles and knees, are the most common locations for nodules to ulcerate. Necrosis of the periarticular fat may rarely occur and, in this setting, patients may also experience arthritis involving the ankles and knees. Even rarer associations include necrosis of abdominal fat or bone marrow fat, pleural effusions, mesenteric thrombosis, and eosinophilia.
Pancreatic panniculitis occurs in the setting of acute or chronic pancreatitis and in the context of pancreatic acinar carcinoma, where panniculitis may herald metastatic disease. Associations with other types of pancreatic cancer, such as islet cell carcinoma, have been reported but occur less frequently. Other less common associations include pancreas divisum, pancreatic pseudocysts, vasculopancreatic fistulas, traumatic pancreatitis, and pancreatitis secondary to sulindac intake. Cases have been reported following endoscopic retrograde cholangiopancreatography (ERCP). Pancreatic panniculitis has also been reported with nonpancreatic entities such as intrahepatic cholangiocarcinoma.
Pancreatic panniculitis can be a presenting feature of subclinical pancreatitis in which elevated amylase and lipase may be the only laboratory abnormalities. It is thought that release of trypsin, lipase, amylase, and other lipolytic enzymes from the pancreas into the circulation results in formation of triglycerides from glycerol esters in the pannus, which leads to necrosis.
Cutaneous disease can precede or follow underlying pancreatic disease; sometimes the cutaneous eruption precedes the typical presentation of pancreatitis by weeks to months.
Resolution of the nodules with scarring may occur within weeks to months after treatment of pancreatitis or after resection of pancreatic carcinoma.
Immunocompromised Patient Considerations:
A single case was reported in a patient with primary HIV infection and a hemophagocytic syndrome.
Pediatric Patient Considerations:
There is one case report of a child with systemic lupus erythematosus treated with prednisone, azathioprine, and hydrochlorothiazide who developed pancreatitis and associated subcutaneous nodular fat necrosis and calcinosis cutis.
M79.3 – Panniculitis, unspecified
403416005 – Panniculitis secondary to pancreatic disease
- Alpha-1 antitrypsin deficiency panniculitis also presents with tender, erythematous nodules on the lower trunk, buttocks, and thighs that ulcerate and drain. This condition may occur in the setting of chronic liver disease with cirrhosis, emphysema, pancreatitis, and vasculitis. Microscopic findings include a predominantly neutrophilic panniculitis with liquefactive fat necrosis. "Skip areas" of normal intervening fat may be seen.
- Nodular vasculitis (erythema induratum) presents as tender, erythematous nodules on the posterior lower legs that ulcerate. Microscopically, a mixed lobular and septal panniculitis with vasculitis involving small- to medium-sized arteries is observed. This condition is associated with tuberculosis.
- Panniculitis due to injection of foreign material into the skin (factitial panniculitis) – Self-injection of various oils (olive, mineral, castor, sesame) causes panniculitis presenting with erythematous, often draining, nodules at sites of injection. Mixed septal and lobular inflammation and varying degrees of fat necrosis are present, along with a "Swiss cheese" appearance of the pannus with varying sizes of cystic spaces.
- Polyarteritis nodosa is a small- and medium-vessel vasculitis that presents with erythematous and purpuric nodules on the lower extremities. Livedo reticularis is a common associated finding.
- Cytophagic histiocytic panniculitis – Subcutaneous nodules that ulcerate and drain, with fever, hepatosplenomegaly, cytopenias, liver failure, intravascular coagulation, and hemorrhage. Microscopically, there is lobular panniculitis with "beanbag" cells representing cytophagocytosis by macrophages.
- Erythema nodosum does not typically occur in the context of pancreatic disease. Tender nodules occur on the anterior legs and do not ulcerate or drain. Histologically represents a septal panniculitis with no necrosis of adipocytes.
- Lupus panniculitis – Tender, erythematous plaques and nodules occurring most commonly on the upper body. Plaques also heal with disfiguring scars. The microscopic appearance is characterized by hyalinization as well as aggregates of lymphocytes in the pannus. Interface dermatitis and dermal mucin may also be present.
- Necrotizing fasciitis – An acutely ill patient initially develops pain out of proportion to the clinical findings and then rapidly spreading necrosis of tissue and ulceration of the affected area.