MODY (Maturity Onset Diabetes of Youth), mitochondrial diabetes, Wolfram syndrome, neonatal diabetes and the group of special syndromes seen due to gene defects that cause insulin resistance are called monogenic diabetes. MODY is an autosomal dominant form of diabetes with a relatively young onset. It constitutes 2-5% of all diabetes cases. The presence of more than one affected family member in extended families has facilitated studies of this type of diabetes. In monogenic diabetes, where patients are often misdiagnosed as type 1 and type 2 DM, the fact that the treatment varies according to the underlying genetic etiology increases the clinical importance of the rare disease. Mutations in the B lymphocyte tyrosine kinase (BLK) locus are in the very rare group. Here, we present a case who presented with hyperglycemia and diagnosed as BLK mutation in the follow-up. A 17-year-old female patient applied to the dermatology department due to psoriasis and was referred to our outpatient clinic due to polyuria, polydipsia and weight loss in the last 2 months. Since the patient had a diagnosis of diabetes in first-degree family members and insulin value was not low at the time of hyperglycemia, a genetic study was performed considering the preliminary diagnosis of MODY and heterozygous mutation of BLK (NMˍ001330465.2):C.1081G˃T(p. Gly361Trp) was detected. Afterwards, the insulin dose was decreased and oral sulfonylurea therapy was started gradually. This type, also called MODY type 11 or BLK mutation, is a very rare type of MODY that has not been studied much. The 8p23, B-lymphocyte kinase (BLK) gene encodes a nonreceptor tyrosine kinase (nrTk) from the protooncogene Src family. The BLK gene is expressed in beta cells and is responsible for insulin synthesis and secretion through the transcription factors Pdx1 and Nkx6.1. nrTk is responsible for cell growth and differentiation. BLK mutation reduces insulin secretion by reducing BLK expression and/or activity. Compared to other MODY types, cases are usually obese phenotype. 60% of cases are treated with insulin. However, sulfonylurea can be tried. There is no publication in terms of diabetes complications. It is noteworthy that the case has a rare mutation and that blood sugar regulation was achieved with oral sulfonylurea therapy, and MODY should be a diagnosis that must be kept in mind in patients with diabetes mellitus in close family members, who do not present with severe ketoacidosis despite hyperglycemia, and who have relatively low insulin levels.
15 Sep 2022 - 17 Sep 2022