Case Report: A Novel ABCC8 Variant in a Chinese Pedigree of Maturity-Onset Diabetes of the Young

The Elusive Nature of ABCC8-related Maturity-Onset Diabetes of the Young (ABCC8-MODY). A Review of the Literature and Case Discussion

PURPOSE OF REVIEW

Maturity-onset diabetes of the young (MODY) are monogenic forms of diabetes resulting from genetic defects, usually transmitted in an autosomal dominant fashion, leading to β-cell dysfunction. Due to the lack of homogeneous clinical features and univocal diagnostic criteria, MODY is often misdiagnosed as type 1 or type 2 diabetes, hence its diagnosis relies mostly on genetic testing. Fourteen subtypes of MODY have been described to date. Here, we review ABCC8-MODY pathophysiology, genetic and clinical features, and current therapeutic options.

RECENT FINDINGS

ABCC8-MODY is caused by mutations in the adenosine triphosphate (ATP)-binding cassette transporter subfamily C member 8 (ABCC8) gene, involved in the regulation of insulin secretion. The complexity of ABCC8-MODY genetic picture is mirrored by a variety of clinical manifestations, encompassing a wide spectrum of disease severity. Such inconsistency of genotype-phenotype correlation has not been fully understood. A correct diagnosis is crucial for the choice of adequate treatment and outcome improvement. By targeting the defective gene product, sulfonylureas are the preferred medications in ABCC8-MODY, although efficacy vary substantially. We illustrate three case reports in whom a diagnosis of ABCC8-MODY was suspected after the identification of novel ABCC8 variants that turned out to be of unknown significance. We discuss that careful interpretation of genetic testing is needed even on the background of a suggestive clinical context. We highlight the need for further research to unravel ABCC8-MODY disease mechanisms, as well as to clarify the pathogenicity of identified ABCC8 variants and their influence on clinical presentation and response to therapy.

A novel mutation in the ABCC8 gene causing maturity-onset diabetes of the young: A case report

A 34-year-old woman was diagnosed with type 1 diabetes mellitus and treated with insulin for 24 years. The patient has a family history of diabetes in three consecutive generations. Her Whole exon sequencing showed a heterozygous mutation in the ABCC8 gene, and it also found some of her relatives to carry this mutation. She was diagnosed with MODY12 and received glimepiride therapy with the achievement of good glycaemic control.

A case report of Maturity-onset diabetes of the young 12: large fragment deletion in ABCC8 gene with literature review

Background

Maturity-onset diabetes of the young (MODY) is one type of monogenic diabetes that is often misdiagnosed. The case refers to a case of maturity-onset diabetes of the young 12 (MODY12) who was misdiagnosed with type 1 diabetes (T1DM), and this was the first case of MODY12 induced by a large deletion of the ATP-binding cassette transporter C8 gene (ABCC8). Additionally, a literature review was conducted regarding the pathological mechanisms, clinical manifestations, diagnosis, and treatment of ABCC8-mutated diabetes.

Case Description

A 22 years old, male patient had been misdiagnosed with T1DM for 4 years and had experienced poor glucose control with multiple daily insulin injections. Their glycated hemoglobin (HbA1c) was 12.9% at the time of admission and they had been experiencing frequent hypoglycemia. Next-generation sequencing found that the chr11p15.1 region had large fragment heterozygous deletion of exon 17 of the ABCC8 gene. According to the genetic test results, the patient was diagnosed as MODY12, insulin treatment was gradually stopped and converted to glimepiride for oral administration, and HbA1c decreased to 6.1%. After oral treatment for 8 months, the glimepride was stopped; however, HbA1c was 5.9% after 6 months of drug withdrawal and C-peptide level became elevated [fasting C-peptide (FCP) increase from 0.8 to 7.5 ng/mL, and 2 h postprandial C-peptide increase from 0.7 to. 4.1 ng/mL].

Conclusions

It is easy for underweight MODY patients to be misdiagnosed with T1DM. For T1DM patients with poor insulin treatment effects, repeated hypoglycemia, and persistent insulin secretion level, ABCC8 or other genes related to monogenic diabetes should be screened. An early diagnosis and transition of treatment can help improve prognosis.