Pediatric Diabetes 2007: 8: 5–10 All rights reserved # 2007 The Authors Journal compilation # 2007 Blackwell Munksgaard Pediatric Diabetes Original Article HLA-DRB1*08 allele may help to distinguish between type 1 diabetes mellitus and type 2 diabetes mellitus in Mexican children Rodrı ´guez-Ventura AL, Yamamoto-Furusho JK, Coyote N, Dorantes LM, Ruiz-Morales JA, Vargas-Alarco ´ n G, Granados J. HLA-DRB1*08 allele may help to distinguish between type 1 diabetes mellitus and type 2 diabetes mellitus in Mexican children. Pediatric Diabetes 2007: 8: 5–10. Background: It may be difficult to distinguish type 1 diabetes mellitus (T1DM) from type 2 diabetes mellitus (T2DM) in the pediatric population. Autoantibodies may help to differentiate both types of diabetes, but sometimes these are positive in patients with T2DM and negative in patients with T1DM. The human leukocyte antigen (HLA)-DR genotype has been associated with T1DM and with T2DM only in adults and in determined cases. Aim: To determine the differences in HLA class II allele frequencies in Mexican children with T1DM and T2DM. Methods: We included 72 children with T1DM, 28 children with T2DM, and 99 healthy controls. All were Mexican, and diabetes was diagnosed according to the clinical and laboratory criteria established by the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. The HLA-DRB1 typing was performed using polymerase chain reaction– sequence-specific oligonucleotide probe and polymerase chain reaction sequence-specific primers. Results: We found an increased frequency of HLA-DRB1*08 and a decreased frequency of HLA-DRB1*04 in the group with T2DM vs. T1DM [p ¼ 0.0001, odds ratio (OR) ¼ 10.58, 95% confidence interval (CI) ¼ 3–40.8 and p ¼ 0.0006, OR ¼ 0.24, 95% CI ¼ 0.11–0.53, respectively]. No significant differences were found between HLA-DRB1 alleles in T2DM vs. controls. In the group with T1DM, there was a significantly increased frequency of the HLA-DR4 and HLA-DR3 alleles relative to controls (p ¼ 0.0000001, OR ¼ 3.59, 95% CI ¼ 2.2–5.8 and p ¼ 0.00009, OR ¼ 4.66, 95% CI ¼ 2.1–10.3, respectively). Conclusion: There are significant differences in the HLA profile in Mexican children with T1DM and T2DM. HLA typing could play a role in the differentiation between both types of diabetes in this population. Ana L Rodrı ´guez-Ventura a , Jesus K Yamamoto-Furusho b , Ninel Coyote a , Luis M Dorantes a , Jorge A Ruiz-Morales b , Gilberto Vargas-Alarco ´n c and Julio Granados b a Department of Pediatric Endocrinology, Hospital Infantil de Me ´xico, Mexico City, Mexico; b Department of Immunology and Rheumatology, Instituto Nacional de Ciencias Me ´ dicas y Nutricio ´n, Mexico City, Mexico; and c Department of Physiology, Instituto Nacional de Cardiologı ´a. Mexico City, Mexico. Key words: T1DM – T2DM – children – HLA – Mexican Corresponding author: Dr Julio Granados Department of Immunology and Rheumatology, Instituto Nacional de Ciencias Me ´ dicas y Nutricio ´n Vasco de Quiroga 15, Colonia Seccio ´n XVI Tlalpan 14000, Me ´xico, D.F., Mexico. Tel: 52 55 54 85 00 80; fax: 52 55 73 20 96; e-mail: kazuofurusho@hotmail.com Submitted 30 December 2005. Accepted for publication 24 August 2006 After the 1990s, type 2 diabetes mellitus (T2DM) in children increased from 1–4% to 8–45% (1–3). Previously referred to as the Ôadult-onset’ form of diabetes, mostly associated with adiposity acquired in middle or older age, T2DM is now being diagnosed in children and adolescents at an alarming rate (4). Although T2DM is more prevalent in the adult, it is possible that with the increasing prevalence of T2DM in children, it may replace type 1 diabetes mellitus (T1DM) as one of the most common chronic diseases in children within one or two decades (5). Risk factors for T2DM include ethnicity (African Americans, Hispanics, Native Americans, and Asian/Pacific Is- landers), risk of overweight [body mass index (BMI) equal to or higher than the 85th percentile but lower than the 95th percentile] or overweight (BMI  95th 5