Overview.
This disease is also known as pancreatic subcutaneous nodular fat necrosis. It is characterized by the recurrent appearance of reddened, painful subcutaneous nodules in batches, 0.5 to 5 centimeters in diameter. The lesions first occur on the lower legs and later spread to the skin all over the body. Some nodules may contain a sterile, sticky substance after the softening phase, and the lesions may be accompanied by paroxysmal abdominal pain, polyarthritis (or arthralgia), fever, and eosinophilia. The lesions are spontaneously invaginated without epidermal atrophy. The incidence of this disease is more common in men than in women, and the ratio of men to women with pancreatic cancer is 5:1, and the age of onset of pancreatic cancer is more than 40 years old.
Etiology
It is currently believed that the fat necrosis that occurs in this disease is due to the action of pancreatic lipase on subcutaneous neutral adipose tissue. Nodules and pancreatitis can occur when there is a sudden rise in serum lipase, and it is also known that the lymphatic system is the main pathway for the dispersion of pancreatic enzymes, but the system of the body circulatory system may play a major role in the operation of pancreatic enzymes.
Symptoms
1. Skin lesions
Purplish-red, painful, inflammatory subcutaneous nodules may appear anywhere on the lower legs bilaterally, but are most commonly found on the skin of the upper inner ankle. The diameter of the nodules varies from a few millimeters to several centimeters. Some larger lesions may be surrounded by swelling. The subcutaneous nodules are adherent to the skin overlying them, but can be moved by touch. In mild cases, there may be only one episode. The nodules do not rupture, but invaginate after two to three weeks, leaving a mildly indented pigmentation. This type of lesion is usually associated with mild abdominal pain, but some patients may have fever and polyarthralgia or arthritis. In more severe patients, fatty tissues other than skin are often involved throughout the body, in addition to the face. Certain large nodules are tender to palpation, resemble abscess-like changes, and have a fluctuating sensation on palpation. If the nodule ruptures spontaneously, it may ooze a white, creamy or oily substance. Several nodules may fuse to form larger fluctuating plaques, with several openings between the nodules to allow transportation to each other. The occurrence of nodules is often accompanied by persistent high fever, general malaise, fatigue, poor appetite and insomnia and other systemic symptoms.
2. Pancreatic lesions
Patients with pancreatic cancer may have different degrees of abdominal pain, mostly dull pain, or colic or knife-like pain in severe cases. It often occurs suddenly, mostly within 2 hours after meals, and gradually intensifies. Mostly located in the middle of the epigastrium, the pain radiates to the lumbar back, and a few may radiate to the shoulders. It usually lasts for 3 to 5 days. Most of the patients in the occurrence of acute pancreatitis, nausea, vomiting, severe cases in the vomit can be mixed with bile. A few patients may have jaundice. Sometimes shock may occur, and the patient may show pale skin, cold sweat, weak pulse, and decreased blood pressure. Physical examination of both lower lungs may hear decreased breath sounds and wet rales. The abdomen is distended and the abdominal muscles are tense, but there is no plate-like abdomen. There is pressure and rebound pain in the epigastric region, bowel sounds are weakened, and sometimes hypokalemia and tachypnoea may occur. More than half of the patients have hepatomegaly, and some patients may develop superficial thrombophlebitis.
Examination
1. Laboratory examination
（Most patients have increased white blood cell counts, eosinophilia, and increased sedimentation rate during episodes.
(2) Stool examination: In patients with pancreatitis, there is an increase in fecal fat content.
(3) Biochemical examination: Calcium can be decreased, gamma globulin increased, serum amylase and lipase increased, which is more obvious in patients with pancreatitis than in those with pancreatic cancer. BSP test is elevated and alkaline phosphatase is elevated in those with pancreatic cancer.
2. Other auxiliary examinations
(1) X-ray examination, retrograde cholangiopancreatography, in chronic pancreatitis, can see irregular narrowing and dilatation of the glandular ducts, sometimes in the form of a rosary, with the branch ends enlarged like a stick, and there can be pseudocysts (i.e., enlarged branches of the glandular ducts) similar to the dilatation of cystic bronchioles. In pancreatic adenocarcinoma, irregular narrowing or obstruction of the pancreatic ducts and signs of twisting and displacement can be seen.
(2) Others If necessary, percutaneous hepatic perforation cholangiography may be performed. Ultrasound and CT examination are helpful in the diagnosis of pancreatic lesions.
Diagnosis
Recurrent painful subcutaneous nodules of purplish-red color appearing on bilateral calves with fever and signs and symptoms of acute and chronic pancreatitis are generally recognized as the disease. Elevated serum amylase or lipase and typical “phantom-like” cells in the adipose tissue of the nodules on biopsy can confirm the diagnosis. In the case of concomitant pancreatic tumor, retrograde cholangiopancreatography, serum amylase examination and CT examination can usually clarify the diagnosis.
Differential diagnosis
1. Erythema nodosum
This disease involves skin, nodules without liquefaction pathological changes, no local depression after the skin lesions subside, serum amylase, lipase are normal, blood eosinophils are normal, no pancreatitis symptoms.
2. Hard erythema
Skin lesions occur in bilateral calf flexion, without fever and pancreatitis symptoms, serum amylase is normal, histopathology is tuberculosis-like changes, anti-tuberculosis treatment is effective.
Complications
Skin nodules can be accompanied by pancreatitis, which can lead to pancreatic cancer in severe cases.
Treatment
The treatment of this disease mainly focuses on pancreatic diseases, and there is no effective treatment for nodular fat necrosis.
1. Systemic treatment
When acute attack occurs with high fever, joint symptoms and skin lesions, antipyretic and analgesic drugs can be used, such as aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs), in order to alleviate joint symptoms and reduce fever. If necessary, glucocorticoids can be used for several days.
2. Treatment of concomitant pancreatitis
Once acute pancreatitis occurs, it should be fully symptomatic treatment, available antipyretic and analgesic drugs to reduce fever, severe abdominal pain can be appropriate amount of morphine analogues to relieve pain, to correct the electrolyte imbalance and acid-base disorder. For chronic pancreatitis, scopolamine drugs such as scopolamine (654-2) and atropine can be given to relieve abdominal pain. A high-sugar, low-fat, high-protein diet is appropriate, and appropriate amounts of digestive aids are routinely administered.
Prognosis
Those with concomitant pancreatic cancer have a poor prognosis and may deteriorate quickly and die. If accompanied by pancreatitis, the prognosis is better, but it is easy to recur.