ESPE Yearbook of Paediatric Endocrinology

Brief summary: This review article draws on existing studies of type 1 diabetes (T1D) in sub-Saharan Africa, examining differences in phenotype, genetic susceptibility and rates of autoimmunity within this population. Lack of large prospective studies with well-standardized methodologies are noted in this population, making more definitive studies necessary.

This article reviews studies reporting the clinical features of patients with T1D in sub-Saharan Africa (SSA), examining both those at or close to diagnosis and those with longer duration diabetes. Understanding the phenotype and etiology of T1D in SSA in challenging due to lack of robust epidemiological and clinical research, difficulties making an appropriate diagnosis and mortality attributable to poor access and management. Case definition is complicated by atypical presentations and poor differentiation between T1D and T2D, including a high rate of lean T2D, high prevalence of ketosis-prone diabetes and diabetes associated with chronic malnutrition. Limited access to classification tests adds to the difficulty. As a result, phenotypic studies may be examining populations with mixed etiologies. With these caveats, a later peak age of onset of T1D is disproportionately reported in SSA, with a peak about a decade later than that observed in Caucasian populations. This may be due to heterogeneity in phenotype or high and early mortality among younger patients with T1D resulting in lack of diagnosis in this age group. Reported incidence of diabetic ketoacidosis ranges from 20 to 80% depending on the population studied. Immunological studies have consistently reported lower rates of islet autoantibodies in SSA that in developed countries which suggests a possible difference in etiological underpinnings. Based on current evidence, GAD antibodies appear to be the single best islet autoantibody to test for in African populations. Differences in genetic susceptibility are also noted with HLA DR3 conferring the highest susceptibility for T1D in SSA.