A 29-years-old male taking oral hypoglycemic drug never had ketonuria in his life. His BMI is 20.5. His grandfather had diabetes and his father who is only son of his grandfather did not have the disease. Which type of DM this person will be most likely -

A number of unusual genetic diseases are associated with diabetes. In rare families, diabetes is caused by single gene defects with autosomal dominant inheritance. These subtypes constitute less than 5% of all cases of diabetes and typically present as 'maturity-onset diabetes of the young' (MODY), i.e. non-insulin-requiring diabetes presenting before the age of 25 years (Box 21.6). Very rarely, diabetes can develop at or soon after bih. This neonatal diabetes is usually genetic in origin, with 50% due to mutations in the KATP channel of the pancreatic b cell causing insulin deficiency and diabetic ketoacidosis. However, sulphonylurea drugs overcome the defect in potassium channel signalling, so that insulin therapy is not necessary in these cases. DAVIDSONS PRINCIPLES AND PRACTICE OF MEDICINE 22ND EDITION PAGE NO-806,807