204-LB: An Unusual Case of Autoantibody-Negative Ketosis-Prone Diabetes (KPD) Secondary to Marked Insulin Resistance

KPD is classically regarded as an atypical form of diabetes caused by near-complete beta-cell failure. A 37-year-old Egyptian man (BMI: 27.7 Kg/m2) presented with hyperglycemia (362 mg/dL) and DKA (arterial pH 7.20, ketonemia 5.0 mmol/L, ketonuria 80 mg/dL). He was afebrile, with recent polyuria, polydipsia and weight loss. HbA1c was 107 mmol/mol (11.9%) and blood tests excluded diabetes secondary to endocrinopathies. SARS-CoV-2 RT-PCR test was negative. IV insulin infusion (0.1 IU/kg/h) and IV fluid therapy were started. He was shortly transitioned to a sc basal-bolus insulin regimen (0.7 IU/kg/day). Mixed-meal tolerance test (MMTT) revealed a peak 120-min stimulated C-peptide of 12.3 ng/mL, suggesting marked insulin resistance. Islet autoantibodies (ICA, IAA, GADA, IA-2A, ZnT8A) and insulin receptor autoantibodies (IgG/IgM) were negative. HLA genotyping detected the following haplotypes: DRB1*01,*04; DQA1*01:01P,*03:01P; DQB1*03:02P,*05:01P. Insulin dose was gradually reduced and insulin therapy was discontinued after 4 months in favor of metformin (2550 mg/day) plus sc semaglutide (up to 1 mg/week). After one year, MMTT revealed a peak 60-min stimulated C-peptide of 8.25 ng/mL. During the 18-month follow-up period, fasting capillary beta-hydroxybutyrate values were <0.2 mmol/L and HbA1c remained <48 mmol/mol (<6.5%), indicating disease remission. This case suggests the existence of an autoantibody-negative KPD subtype driven by marked insulin resistance rather than by insulinopenia.