A case of latent autoimmune diabetes in the young positive for zinc transporter 8 antibody with type 2 diabetes characteristics

Latent autoimmune diabetes in the young (LADY), also known as slowly progressive insulin-dependent diabetes mellitus (SPIDDM), is a slowly progressive form of type 1 diabetes (T1D) characterized by positive islet-related autoantibodies and, typically, an initial type 2 diabetes (T2D) phenotype. Although approximately 10% of children with T2D have positive islet-related autoantibodies, reports on the clinical course of patients with LADY are limited. We present the case of a 17-yr-old female initially diagnosed with T2D based on a body mass index (BMI) of 27 kg/m², obesity, and preserved endogenous insulin secretion. Notably, the glutamic acid decarboxylase antibody (GADA) test results fluctuated between weakly positive and negative. She developed diabetic ketosis 9 mo later, with a weak GADA titer and a high zinc transporter-8 antibody (Zn-T8A) titer, confirming autoimmune β-cell destruction consistent with T1D. Subsequent human leukocyte antigen (HLA) testing revealed the presence of the DRB1*15:02-DQB1*06:01 haplotype, which is considered protective against T1D. This case report details the clinical course of LADY, emphasizes close follow-up and re-evaluation of multiple islet-related autoantibodies in patients to distinguish LADY from T2D, and suggests that a protective HLA haplotype may have contributed to the slow onset despite high-titer Zn-T8A.