What feature most strongly suggests maturity-onset diabetes of the young in a patient?

In the context of identifying maturity-onset diabetes of the young (MODY), a family history of diabetes mellitus is the most indicative feature. MODY is characterized by early onset diabetes (typically before the age of 25) that runs in families, often demonstrating an autosomal dominant inheritance pattern. Therefore, a strong family history of diabetes mellitus strongly suggests a genetic component related to MODY.

A poor response to glipizide therapy is more commonly associated with type 2 diabetes rather than MODY, where patients typically respond well to sulfonylureas as they often have preserved beta-cell function early in the disease course.

Recurrent episodes of diabetic ketoacidosis are more characteristic of type 1 diabetes or other forms of diabetes that involve absolute insulin deficiency rather than MODY.

X-linked recessive inheritance does not apply to MODY, which is generally inherited in an autosomal dominant manner, further distancing this option from a correct identification of the condition.

Thus, a strong family history of diabetes mellitus aligns most coherently with the diagnosis of maturity-onset diabetes of the young, denoting its hereditary nature and the patterns of inheritance associated with this specific type of diabetes.