It is no surprise that diabetes, type I (insulin-dependent) and type II (non-insulin-dependent), is a public health issue. The numbers are astonishing. In 2007 terms, 23.6 million people (7.8% of the population) were estimated to have diabetes, about 186,300 of them under the age of twenty (stats courtesy of NIDDK). To add insult to injury, there is a laundry list of complications associated with diabetes, including increased risk for heart disease, stroke, and kidney failure (to name a few).

But did you know there are rare forms of diabetes that are not classified as either type I or type II? Thanks to improvements in genetic testing over the last decade, there has been an increase in newly identified monogenic forms of diabetes¹. These forms of diabetes arise from single gene mutations that result in the diabetic phenotype.

I was lucky enough to attend a talk this week by geneticist Wendy Chung, MD, PhD of Columbia University, who has treated many patients with monogenic forms of diabetes. In particular, Chung discussed how genetic testing has aided in the diagnosis and treatment of one form of monogenic diabetes, maturity onset diabetes of the young (MODY). MODY is an autosomal dominant form of diabetes that results from a mutation in one of eight different genes. Depending on which type of MODY a patient has (i.e. the particular gene mutation), treatments for this disease vary greatly. Treatment of MODY2, which results from a mutation in the glucokinase gene, requires only proper diet and weight management. This is because patients with MODY2 present only modestly high levels of fasting glucose, which typically remain stable throughout life. In contrast, MODY3 (HNF-1alpha mutation), MODY1 (HNF-4alpha mutation), and MODY5 (HNF-1beta mutation) require more aggressive treatments, such as oral hypoglycemic agents and insulin injections to maintain proper blood glucose levels.

It is clear that molecular testing is essential for proper diagnosis and treatment of diseases like mongeneic forms of diabetes, so why not screen for all rare diseases like these? The main issue is cost. Presently, molecular testing for rare diseases is often performed in academic laboratories, which can be slow and expensive. There is simply not enough demand for a wide scale diagnostic test for rare diseases. However, as genotyping becomes more efficient and regents less expensive, screening for rare diseases may become more widely available. Until then, you just have to hope mom and dad gave you some good genes.

¹ To read more about the various forms of monogenic diabetes, I refer you to this review article.