Type 5 diabetes: A comprehensive review to understand the basis of diabetes of poverty.

Malnutrition-Related Diabetes Mellitus (MRDM) is a subtype of diabetes associated with chronic malnutrition, primarily observed in low- and middle-income countries (LMICs) and impoverished populations. The disease is characterized by onset in young, lean patients with a history of chronic undernutrition, insulin deficiency, persistent insulin sensitivity, and resistance to ketosis. MRDM was recognized by the World Health Organization (WHO) in 1985, then removed from classification in 1999 due to a lack of evidence. Emerging evidence has revealed a unique pathophysiology, prompting the International Diabetes Federation (IDF) to officially recognize MRDM as "Type 5 Diabetes" (T5D). This review synthesizes the evidence that validates T5D as a distinct endotype, which is mechanistically different from other diabetes types. It delineates the epidemiological patterns of T5D and focuses on the pathophysiological "blueprint" of the malnourished pancreas. It also integrates evidence showing how early-life nutritional deprivation, including protein and micronutrient deficiencies, programmatically reduces β-cell mass and function through mechanisms such as mitochondrial dysfunction, endoplasmic reticulum stress, oxidative damage, and persistent epigenetic modifications. Current management strategies and the distinct profile of long-term complications are highlighted. Finally, the review outlines pressing future directions, arguing that the formal recognition of T5D provides an opportunity for coordinated research and policy initiatives that address the root causes and consequences of this diabetes of poverty.