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

Endocrine Abstracts (2019) 63 P947 | DOI: 10.1530/endoabs.63.P947

Autoimmune diabetes mellitus versus idiopathic: differences at diagnosis

Diana Silva1, Diana Catarino1, Cláudia Pereira2, Luísa Ruas1, Cristina Ribeiro1, Nelson Cunha1, Lúcia Fadiga1, Joana Guiomar1, Luís Cardoso1, Isabel Paiva1 & Francisco Carrilho1


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 categories for the classification of type 1 diabetes mellitus (DM): autoimmune (AI) and idiopathic (ID). The absence of autoimmune markers or association with HLA haplotypes defines the second category. Only a small minority of patients with type 1 diabetes fall into this category.

Objective: To evaluate the clinical characteristics of both categories and to analyze the differences between them.

Methods: Retrospective cohort study, based on clinical records of patients with not detected C-peptide, in which autoantibodies related to DM were assayed. Only those patients whose measurements were taken at the time of diagnosis of diabetes mellitus were included, to include only type 1 DM patients, without clinical suspicion of another type of diabetes. We obtained two groups: one with positive autoimmunity – type AI (≥1 positive antibody) and another with negative autoimmunity – type ID. Age, family history, anthropometry, duration of symptoms, form of presentation, blood glucose at admission, HbA1c, lipid profile and arterial hypertension were evaluated. Results were considered statistically significant with P<0.05.

Results and conclusions: A total of 37 patients were selected, of whom 29 had positive autoimmunity and 8 had negative autoimmunity. The age of diagnosis of the type AI differed significantly from the type ID (23 years vs 38.1 years, respectively) (P=0.004). The body mass index at diagnosis did not differ significantly (P=0.435) between the two groups. There was no statistically significant association between the groups and the family history of type 1 DM or type 2 DM. The duration of symptoms differed significantly (P=0.003), with a duration of 21.8 days (AI) vs 45.0 days (ID), but there was no difference between groups and disease presentation (P=0.744). The blood glucose at admission did not differ significantly (P=0.482), as the HbA1c at diagnosis (P=0.794). The lipid profile did not differ significantly, although total and LDL cholesterol levels were higher in ID group. The percentage of patients with dyslipidemia and arterial hypertension did not differ significantly. The total daily insulin dose at discharge did not differ significantly (P=0.301). In conclusion, there was a statistic difference in the age and the duration of symptoms, that is, patients with negative autoimmunity were older and had a longer duration of symptoms, and presented a tendency for an atherogenic lipid profile, resembling a clinical phenotype of type 2 DM.