It takes a complex and not fully understood interplay of genes and environment to bring on type 1 or type 2 diabetes. But in several lesser-known kinds of diabetes—all grouped under the umbrella term maturity-onset diabetes of the young, or MODY—the disease is caused by just a single aberrant gene.
Each type stems from a mutation in a different gene, and collectively MODY accounts for an estimated 1 to 5 percent of all diabetes. The estimate is rough because MODY is often misdiagnosed as type 1 or type 2.
While the immune system misfires in type 1 and insulin resistance characterizes type 2, MODY stems from problems in a set of genes that regulate the body's flow of insulin. A faulty gene means the pancreas can't make enough insulin, leading to diabetes.
MODY is highly heritable. If one parent has a gene that causes MODY, there is a 50 percent chance it will be passed to a child. However, not everyone who inherits a MODY gene develops diabetes.
People usually find out they have MODY before the age of 25, often when high blood glucose forces a trip to the doctor or emergency room. However, in some cases, symptoms are so mild that the condition remains hidden until later in life.
If a doctor suspects that someone has MODY, genetic testing can confirm the diagnosis. By pinpointing the mutated gene, a doctor may be able to customize treatment. For example, some MODY subtypes don't require treatment with insulin and can be controlled with oral medications. Screening is useful since MODY is hereditary; if one person in a family has it, there are likely to be others.