ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 63 P929 | DOI: 10.1530/endoabs.63.P929

Idiopathic versus autoimmune type 1 diabetes - long-term differences

Diana Catarino1, Diana Silva1, Cláudia Pereira2, Cristina Ribeiro1, Luísa Ruas1, Nelson Cunha1, Lúcia Fadiga1, Joana Guiomar1, Mariana Lavrador1, Inês Vieira1, Luís Cardoso1, Isabel Paiva1 & Margarida Bastos1

1Endocrinology Department - Coimbra Hospital and University Centre, Coimbra, Portugal; 2Clinical Pathology Department - Coimbra Hospital and University Centre, Coimbra, Portugal.

Introduction: The American Diabetes Association proposed two subcategories for type 1 diabetes: autoimmune type 1 diabetes (ADM) and idiopathic type 1 diabetes (IDM). The absence of β-cell autoimmune markers and lack of association with HLA haplotypes define the second category, whose pathogenesis remains unclear. Only a minority of patients with type 1 diabetes fall into this subcategory which is considered by several authors similar to type 2 diabetes.

Objective: The aim of this study is to compare long term (ten years) differences between these two categories.

Methods: Retrospective cohort study, based on clinical records of patients with undetectable c-peptide, in which β-cell autoimmune markers were performed (islet cell antibodies, insulin antibodies, glutamic acid decarboxylase antibodies, islet antigen-2 antibodies). Only patients with assays at the time of the diagnosis of diabetes were considered and were excluded patients with suspicion of another specific type of diabetes. We obtained two groups of patients: ADM - with positive autoimmune markers (≥ 1 positive antibody), and IDM - with negative autoimmune markers. We analysed the following differences: body mass index (BMI), A1C, lipid profile, hypertension, total diary dose of insulin (TDDI), microvascular and macrovascular complications. Statistical significance - P value 0,05.

Results: We obtained 37 patients, 29 with ADM - median age 23,0(9) years; and 8 patients with IDM - mean age 38.1±12.8 years. Evaluation of BMI showed no statistical difference between groups (ADM:25.14 kg/m2; IDM: 22.58 kg/m2; P=0,079). Relative to A1C we found statistical difference, (ADM:8.7%; IDM: 7.4%; P=0.008) as well as the TDDI (ADM:52.35 units; IDM:33.5 units; P=0.017). Although there was no difference in the proportion of patients with dyslipidaemia, it was higher on the ID group (44.8%-ADM; 62.5%-IDM). Relative to the lipid profile (total cholesterol, LDL and HDL cholesterol and triglycerides), there was no significant difference, however the LDL cholesterol and triglycerides were higher on the IDM group. The proportion of patients with hypertension was higher on IDM group (17.2%- ADM; 25%- IDM group), although there was no significant difference. Relative to microvascular complications, there was no difference in the proportion of retinopathy, neuropathy and nephropathy, but that was higher on the ADM group. There was no difference on the macrovascular disease.

Conclusion: This study showed that at long-term follow-up, patients with ADM have a poor metabolic control, with higher A1C and higher TDDI. Although no significant, patients with IDM have a tendency to more comorbidities (hypertension, dyslipidaemia) and lower microvascular complications.