Clinical paradox: insulinoma in a patient with type 1 diabetes mellitus

Insulinoma is a rare neuroendocrine tumor occurring from beta-cells of the pancreas. Тhe diagnosis of insulinoma may be difficult, especially in patients with concomitant diabetes mellitus. The reason for the similar clinical picture in these patients could be an incorrect scheme of hypoglycemic therapy. There is a number of cases of insulinoma in patients with type 2 diabetes mellitus described in literature. A more paradoxical clinical situation is the development of insulinoma in a patient with type 1 diabetes mellitus (T1DM). Analyzing a huge amount of literature sources, only three articles describing insulinoma in patients with T1DM were discovered. In all the described cases, the tumors turned out to be malignant. We present the first described in literature clinical case of the diagnosis and treatment of insulinoma in a patient with latent autoimmune diabetes in adults (LADA-diabetes), as well as the review of the literature on this topic. A gradual decrease in the need for exogenous insulin in combination with recurrent hypoglycemia made it possible to suspect the diagnosis, which was confirmed during a fasting test and instrumental examination of the tumor using computer tomography and endoscopic ultrasound.