INSR and diabetes mellitus: While this review focuses on selected syndromic forms of rare diabetes, such as WS, AS, BBS, and MODY, it is important to acknowledge that diabetes also occurs in the context of other rare conditions, including syndromes characterized by severe insulin resistance (e.g., congenital generalized lipodystrophy and INSR mutations) or autoimmune polyendocrine syndromes (e.g., IPEX and APS-1).