Pitfalls in the diagnosis of insulin autoimmune syndrome (Hirata's disease) in a hypoglycemic child: a case report and review of the literature

Background Insulin autoimmune syndrome (IAS) is a rare cause of hyperinsulinemic hypoglycemia (HH) not addressed as a potential differential diagnosis in current pediatric guidelines. We present a case of IAS in a child with no previous history of autoimmune disease, no previous intake of triggering medications and absence of genetic predisposition. Case presentation A 6-year-old boy presented with recurrent HH (blood glucose of 26 mg/dL [1.4 mmol/L] and insulin of 686 μU/mL). Abdominal imaging was normal. After multiple therapeutic failures, we hypothesized misuse of exogenous insulin and factitious hypoglycemia. Council of Guardianship had the child separated from his mother, but insulin levels remained high. A chromatography test was then performed which showed high titers of endogenous insulin autoantibody (IAA) with early dissociation from the insulin molecule. The human leukocyte antigen (HLA) test showed a DRB1 *13:01/*08:02 genotype. The patient was advised to control food intake and physical activity routines. During a 5-year follow-up, hypoglycemic episodes were sparse, despite high insulin levels. Conclusions Misdiagnosis of IAS with factitious hypoglycemia may happen if IAS is not considered as a differential diagnosis, leading to potential traumatic consequences. Further efforts should be made to increase awareness of IAS as a differential diagnosis of hypoglycemia and to include it in pediatric guidelines.

Clinical application of ACMG-AMP guidelines in HNF1A and GCK variants in a cohort of MODY families

Maturity-onset diabetes of the young (MODY) is a form of monogenic diabetes with autosomal dominant inheritance. GCK -MODY and HNF1A -MODY are the prevalent subtypes. Currently, there is growing concern regarding the correct interpretation of molecular genetic findings. The American College of Medical Genetics and Genomics (ACMG) updated guidelines to interpret and classify molecular variants. This study aimed to determine the prevalence of MODY ( GCK / HNF1A ) in a large cohort of Brazilian families, to report variants related to phenotype, and to classify them according to ACMG guidelines. One hundred and nine probands were investigated, 45% with clinical suspicion of GCK -MODY and 55% with suspicion of HNF1A -MODY. Twenty-five different variants were identified in GCK gene (30 probands-61% of positivity), and 7 variants in HNF1A (10 probands-17% of positivity). Fourteen of them were novel (12- GCK /2- HNF1A ). ACMG guidelines were able to classify a large portion of variants as pathogenic (36%- GCK /86%- HNF1A ) and likely pathogenic (44%- GCK /14%- HNF1A ), with 16% (5/32) as uncertain significance. This allows us to determine the pathogenicity classification more efficiently, and also reinforces the suspected associations with the phenotype among novel variants.