We present our case to emphasize that monogenic diabetes should be considered in young patients having positive family history and whom diabetes could not be classified.
A 25-year-old female was referred to our clinic due to elevated blood glucose. The patient had no symptoms of hyperglycemia. She had no chronic illness and did not take any medication. Her 55-year-old mother has been followed for uncomplicated diabetes for 16 years with oral antidiabetics, and her 75-year-old grandmother had uncomplicated diabetes for 30 years treated with basal insulin. On physical examination, vital signs were stable, height 168 cm, body weight 70 kg, BMI 24.8 kg/m2. Systemic examination was normal, and no findings of insulin resistance were present.
Laboratory findings revealed that fasting plasma glucose (FPG) was 140 mg/dL, postprandial plasma glucose 178 mg/dL, and HbA1C 7.2%. Blood count and biochemical parameters were normal. Fasting C-peptide was 2.32 ng/mL, urine ketone negative, anti-GAD, ICA, and anti-insulin antibodies were negative. We recommended life-style modifications and metformin treatment. Then, considering the patient age, family history of diabetes, absence of insulin resistance, negative autoantibodies, and normal body mass index, we performed genetic analysis for maturity-onset diabetes of the young (MODY). Heterozygous mutation of p.R191W (c.571C>T) was detected in glucokinase gene, and diagnosis of MODY type 2 was confirmed. She was followed with life-style modifications without metformin. FPG and glucose tolerance test results of siblings of the patient were normal. Genetic screening was recommended for the family.
It may be difficult to determine the type of diabetes in young patients. In suspected cases, genetic analysis may help to establish the definite diagnosis of MODY.