A rare tumor of pancreas caused by mutations in the GCGR gene characterized by pancreatic alpha cell hyperplasia, pancreatic neuroendocrine tumors and markedly increased serum glucagon levels in the absence of a glucagonoma syndrome. Clinical manifestations may include abdominal pain, pancreatitis, fatigue, diarrhea, and diabetes mellitus. The disease is GCGR-related hyperglucagonemia (MONDO_0018582, a Monarch Disease Ontology identifier). Also known as: MVAH, Mahvash disease, alpha-cell hyperplasia with glucagonemia, nesidioblastosis alpha cell hyperplasia microglucagonoma and nonfunctioning islet cell tumor, nesidioblastosis alpha cell hyperplasia microglucagonoma and nonfunctioning islet cell tumour, nesidioblastosis, alpha cell hyperplasia, microglucagonoma, and nonfunctioning islet cell tumor, nesidioblastosis, alpha cell hyperplasia, microglucagonoma, and nonfunctioning islet cell tumour.