Rarer Subtypes: HNF1B and Others

Beyond the three common subtypes, more than 20 genes have been identified as causing monogenic diabetes. Most are rare, and a few are worth knowing about because they involve organs other than the pancreas.

HNF1B is the most important of these. It causes diabetes and kidney abnormalities together, often cystic kidney disease. That combination changes the picture substantially: the kidney involvement is caused directly by the gene rather than by years of high blood glucose, so it can be present early and needs monitoring in its own right.

If you have diabetes alongside kidney cysts or structural kidney abnormalities, that pairing is worth raising specifically — it is a recognisable pattern rather than a coincidence.

ABCC8 appeared in the Asian Indian clinic study, accounting for 8.8% of confirmed MODY cases. The same gene more commonly causes neonatal diabetes, and it affects the potassium channel involved in insulin release — which has treatment implications.

Other rarer forms include mitochondrial diabetes, where diabetes travels with hearing loss, and recessive forms needing an altered copy from both parents.

The practical point is not to learn the list. It is that if your diabetes comes alongside something unexplained in another organ — kidneys, hearing, liver — that combination is worth mentioning, because it may be the clue that identifies the gene.