Glucagonoma is a rare functioning pancreatic neuroendocrine tumour (pNET) arising from pancreatic alpha cells, accounting for <5% of pNETs (1,2). Glucagonoma syndrome comprises necrolytic migratory erythema (NME), type 2 diabetes mellitus (DM), weight loss, or glossitis along with an elevated glucagon level (3,4).
A 74-year-old man was referred by the dermatology service with a two-month history of an erosive buttock rash suspicious for NME in addition to deterioration in diet-controlled DM (HbA1c 6.6% to 8.5%) with no associated weight loss. Skin biopsy was non-diagnostic and demonstrated non-specific psoriasiform dermatitis without the vacuolated keratinocytes characteristic of NME. Fasting glucagon, vasoactive intestinal peptide and pancreatic polypeptide was elevated at >522 pg/mL, 283.0 pmol/L and 112.4 pmol/L (reference range ≤208 pg/mL, 7.3-25.4 pmol/L, 0.0-100.0 pmol/L). MRI identified an indeterminate 8×16 mm T2-hyperintense lesion in the pancreatic tail, and subsequent 68Ga-DOTATATE PET confirmed intense tracer uptake (SUVmax 20.8) without metastatic disease. Histology from surgical resection confirmed a 12 mm grade 1 pNET (Ki67 <3%), with immunohistochemistry and post-operative glucagon levels pending. The rash resolved rapidly following resection.
Glucagonoma syndrome reflects the systemic catabolic effects of chronic hyperglucagonaemia. Diagnostic criteria are not formally established; NME is considered near-pathognomonic of the syndrome (5). The 2023 ENETS guidance suggests that glucagon levels above 500 pg/mL support the diagnosis (5). At diagnosis tumour size is typically large, and metastatic disease is commonly present, in contrast to this case (6). Surgical resection is first-line therapy for non-metastatic disease and aids symptom control in metastatic disease; somatostatin analogues are the first-line medical therapy where surgery is not pursued, or can serve as adjunctive therapy (3-5).
Glucagonoma should be considered in patients with deterioration in diabetes and an atypical dermatosis. The diagnosis is supported by markedly elevated glucagon levels and 68Ga-DOTATATE avidity. Surgical resection remains the first-line, and potentially curative, treatment.