Type 5-Diabetes: A Forgotten Phenotype Finds its Name

On April 8 2025, a landmark development was announced at the International Diabetes Federation (IDF) World Diabetes Congress in Bangkok. The IDF formally recognized a long-overlooked and poorly understood form of diabetes malnutrition-associated as diabetes Type 5 Diabetes (T5D).¹ This pivotal recognition heralded a transformative moment for the global understanding of diabetes, especially in low and middle-income countries (LMICs), where this condition remains underdiagnosed and mismanaged.

Historically, diabetes classifications have included Type 1 (autoimmune insulin deficiency), Type 2 (insulin resistance), Type 3 (monogenic or secondary diabetes), and Type 4 (gestational diabetes).² The newly designated Type 5 Diabetes represents a distinct clinical and meta bolic phenotype.

Malnutrition-related diabetes first noted in Jamaica by Hugh-Jones in 1955. Later, similar cases surfaced across Ethiopia, Nigeria, Bangladesh, Korea, and India, primar ily affecting lean, malnourished young males with a BMI <19 kg/m². It was noteworthy that such cases were seen in low and middle-income countries.

These individuals displayed no signs of ketosis despite having hyperglycaemia, contrasting with Type 1 diabetes, and often suffered hypoglycaemia with standard insulin therapy. Recognizing its atypical profile, the World Health Organization (WHO) initially included this entity as malnutrition-related diabetes mellitus (MRDM) in 1985.³ However, due to inconsistent findings linking malnutrition and diabetes pathogenesis, the WHO removed it from its classification. However, accumulating evidence continued to support its uniqueness.⁴

 Recent metabolic studies led by Meredith Hawkins and her team, involving 73 Asian Indian men, confirmed that this form of diabetes is not driven by insulin resistance, as previously thought.^5,7 Instead, individuals with Type 5 Diabetes showed poor insulin secretion, increased glucose uptake, low visceral adiposity, and reduced hepatocellular lipids. These characteristics substantiate the argument for classifying it as a distinct entity, separate from Type 1 and Type 2 diabetes.

The clinical implications are profound. Misclassification often leads to inappropriate insulin use, heightening the risk of fatal hypoglycaemia. Individuals with Type 5 Diabetes typically respond better to minimal insulin doses, oral hypoglycaemic agents, and dietary modification, spe cifically a high-protein, low-carbohydrate diet.

Type 5 Diabetes predominantly affects populations in low and middle-income countries (LMICs) and contributes to the diabetes burden in these regions. Clinical features often include early-onset diabetes in malnourished young adults, male predominance, negative autoantibodies (GAD-65 and IA-2), absence of ketosis, and a preserved C-peptide response.

A unified diagnostic framework is urgently required to consolidate global understanding and clinical management. Type 5 Diabetes must be incorporated into nation al diabetes guidelines. This reclassification will inform training modules for healthcare workers, prevent misdiagnosis, and promote appropriate therapy.

We urge researchers, policymakers, and clinicians to expand collaborative studies, particularly in low and middle-income countries to investigate the epidemiology, pathophysiology, and long-term outcomes of Type 5 Diabetes. The WHO and International Diabetes Federation should initiate an updated classification effort incorporating this evidence to address the overlooked burden of malnutrition-related diabetes.

Summary Box: Malnutrition-Related Diabetes (Type 5 Dibabetes)

1. Recognition: On 8 April 2025, the International Diabetes Federation (IDF) formally recognized malnutrition-related diabetes as a distinct category, officially naming it as ‘Type 5 Diabetes’.
2. Clinical Features: Typically affects lean, malnourished young adults (BMI <19 kg/m²) with no ketoacidosis and negative diabetes autoantibodies. Patients exhibit preserved insulin production but paradoxically they require minimal insulin.
3. Historical Context: It was first observed in Jamaica (1955) and later across India, Ethiopia, Nigeria, Bangladesh, and Korea. WHO initially classified it as MRDM in 1985 but later removed it from the classification.
4. Recent Evidence: Studies led by Meredith Hawkins and Nihal Thomas at Global Diabetes Institute at Albert Einstein College of Medicine, Bronx, N.Y. USA and Christian Medical College & Hospital, Vellore, Tamil Nadu, India confirm that Type 5 Diabetes is a unique phenotype with reduced insulin secretion, increased glucose uptake, low visceral fat, and abnormal metabolic profiles.
5. Call for Action: Updated diabetes classification guidelines, tailored management strategies, and research focus in low and middle-income countries are urgently needed.
6. Implication: Misdiagnosis with Type 1 or Type 2 can lead to fatal outcomes. Distinct management involving nutritional rehabilitation and minimal pharmacologic insulin is vital.

Conflicts of Interest

Nil