ABSTRACT
Diabetes mellitus is an etiologically and clinically heterogeneous group of disorders with hyperglycemia as the shared feature. Type 1 and type 2 diabetes make up the vast majority of cases seen by primary physicians. However, hyperglycemia or impaired glucose tolerance is a feature of a large number of illnesses and genetic syndromes that are collectively termed secondary forms of diabetes (classification from the American Diabetes Association is shown in Table 1). Although many are rare, each has characteristic clinical features that are of diagnostic value, and the onus is on practicing physicians to have some familiarity and a high index of suspicion. A useful rule is if a patient presents with features in the history, physical examination, or laboratory evaluation that seem atypical for type 1 or type 2 diabetes, then a careful evaluation of secondary forms of diabetes is warranted. This chapter provides an overview of the more common types following the format of Table 1.
