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Glucagonoma is a rare, functioning type of pancreatic neuroendocrine tumor (PNET; see this term) that hypersecretes glucagon, leading to a syndrome comprised of necrolytic migratory erythema, diabetes mellitus, anemia, weight loss, mucosal abnormalities, thromboembolism, gastrointestinal and neuropsychiatric symptoms.
ORPHA:97280Classification level: Disorder
The estimated incidence in the general population is 1/20, 000,000.
Glucagonoma usually presents in the fifth decade of life with the initial symptom often being necrolytic migratory erythema. This skin condition is characterized by a red, blistering and migratory rash, associated with an intense pruritus and that is mainly localized to the lower extremities and the groin. Diabetes is present in most cases and requires insulin therapy. Weight loss, anemia, mucosal abnormalities (glossitis, cheilitis, stomatitis), gastrointestinal disturbances, thromboembolism and neuropsychiatric symptoms (depression) are other frequent manifestations. Most glucagonomas have already metastasized by the time that they are diagnosed, mainly to the liver. In some cases glucagonoma may be associated with multiple endocrine neoplasia type 1 (MEN1; see this term). Glucogonoma can be non-functioning in rare cases.
The etiology is unknown. These tumors of 2-25 cm mainly occur in the tail of the pancreas. They synthesize and secrete glucagon, which is responsible for balancing the effects of insulin, and is therefore essential in regulating blood sugar levels.
Diagnosis is based on clinical findings and endocrine tests. Serum glucagon levels are markedly elevated (>500 pg/mL) and levels of more than 1000 pg/mL are considered diagnostic if the patient also displays features of glucagonoma syndrome. Other hormones such as insulin, somatostatin and vasoactive intestinal peptide may also be elevated. Levels of blood chromogranin A are increased. Localization of tumors is possible by computed tomography (CT) scan, octreotide scan, magnetic resonance imaging (MRI) and/or endoscopic ultrasound.
Differential diagnoses include familial hyperglucagonemia, autoimmune and hereditary chronic pancreatitis, Mahvash disease, acrodermatitis enteropathica (see these terms) and cirrhosis.
Management and treatment
Somatostatin analogues (octreotide or lanreotide) are usually effective in leading to a remission of rash in most patients as well as improving the symptoms of weight loss, abdominal pain and diarrhea. Glycemia is managed by insulin injections or anti-diabetic drugs. Parenteral nutrition (with essential fatty acids, amino acids, vitamins and minerals) may also be necessary. Surgical resection is the only curative option in localized cases. Surgical debulking followed by chemotherapy may be an option in extensive tumors. Resection of the lymph nodes, spleen and parts of the liver containing metastasized glocagonoma may also be necessary. As thromboembolic complications can occur, blood thinners (antiplatelets and anticoagulants) may be recommended.
The prognosis of glucagonoma is usually poor as most have metastasized by the time that they are discovered. Those associated with MEN1 usually have a fairer prognosis as they are diagnosed sooner.