This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skin, Subject name: Medicine
This patient had a 4-year history of diabetes. What is the diagnosis? 
Select and explain. 
A. Bullous disease of diabetes, B. Necrobiosis lipoidica diabeticorum, C. Necrolytic migratory erythema, D. Pigmented purpuric dermatosis
C: Necrolytic migratory erythema
Answer: C: Necrolytic migratory erythema 
Explanation: Answer C. Necrolytic migratory erythemaGlucagonomas are rare neuroendocrine tumors that can cause diabetes and a rash known as necrolytic migratory erythema, which has a characteristic annular pattern of erythema with central crusting and bullae. The rash resolved after excision of a 7-cm glucagonoma from the tail of the pancreas.