Genetic counseling in monogenic diabetes GCK MODY

Introduction. Genetic testing in families with monogenic GCK MODY has predictive, diagnostic, and preventive utility. Predictive tests relate to people who have no features of the disorder themselves at the time of testing. Diagnostic tests relate to family members who have been previously diagnosed with diabetes mellitus or glucose metabolism disturbances. The preventive value of genetic testing for families is to raise awareness of the circumstances leading to glucose metabolism disorders. Aim. The detection of mutation carriers among family members of patients with GCK MODY and the determination of the clinical significance of the genetic test result. Methods. The study group included 27 families of adolescent patients with GCK MODY (39 (75%) of parents and 19 (73.08%) of siblings) monitored in the Department of Pediatrics, Endocrinology and Diabetes and in the Diabetes Clinic of John Paul II Upper Silesian Child Health Centre in Katowice in the years 2007-2012. Subjects underwent a blood sample drawing for genetic and biochemical testing. Results. Through the genetic diagnostics we diagnosed GCK MODY in 14 (63.64%) mothers, 6 (35.29%) fathers and in 7 (36,84%) siblings. Genetic testing has contributed to the detection of 7 (26.92%) asymptomatic carriers of GCK gene mutation among parents and 3 (15,79%) asymptomatic carriers among siblings declaring no carbohydrate metabolism disturbances (before genetic testing there were no indications suggesting carbohydrate metabolism disturbances; OGTT were performed after positive genetic testing). Conclusions. Each case of mutation detection, which is the cause of monogenic diabetes in a patient, justifies the genetic testing in other members of his/her family. Awareness of the genetic status may allow sick family member to confirm the diagnosis, while asymptomatic mutation carriers could benefit from an early clinical observation. Consequently, in each case it gives an opportunity to take diagnostic and therapeutic measures in accordance with the current state of knowledge.