Genotype and Phenotype Heterogeneity in Neonatal Diabetes: A Single Centre Experience in Turkey

Clinical and molecular characteristics of infantile-onset diabetes mellitus in Egypt

PURPOSE

In patients diagnosed with diabetes mellitus (DM) before the age of 12 months, there is an increasing recognition of diabetes caused by single-gene mutations, also known as monogenic diabetes of infancy or neonatal DM (NDM). This study aimed to classify patients at Alexandria University Children's Hospital (AUCH) diagnosed with infantile-onset DM into type 1 DM (T1DM) or NDM and to detect differences in molecular characteristics of NDM patients at our center in comparison to other countries.

METHODS

This retrospective/prospective observational study was conducted on 39 patients diagnosed with infantile-onset DM (age of onset ≤1 year) at AUCH from January 2003 to November 2020. The patients were divided into 2 groups according to age at the onset of DM: ≤6 months and >6-12 months. Molecular testing was done in patients diagnosed with DM at ≤6 months and those with negative autoantibodies.

RESULTS

Twelve patients were diagnosed with DM at age ≤6 months and 27 patients were diagnosed between 6-12 months. Seventeen patients (43.6%) had T1DM, whereas 9 patients (23.1%) had genetically confirmed NDM, including 3 harboring novel mutations. The most common genetic causes of NDM were EIF2AK3 mutations (n=3), followed by KCNJ11 (n=2) and ABCC8 (n=2). Other mutations included SLC19A2 (n=1) and INS (n=1). Three patients with potassium ATP channel mutations were transferred from insulin to sulfonylurea treatment.

CONCLUSION

It is essential to identify patients with NDM clinically and confirm the diagnosis by molecular testing to distinguish them from T1DM as it helps in refining their management, predicting prognosis, and guiding genetic counseling.

Genetic and clinical heterogeneity of permanent neonatal diabetes mellitus: a single tertiary centre experience

AIMS

Neonatal diabetes mellitus (NDM) is a rare disease where diabetes presents during the first six months of life. There are two types of this disorder: permanent neonatal diabetes (PNDM) and transient neonatal diabetes mellitus (TNDM). PNDM occurs due to mutations in genes involved in either beta-cell survival, insulin regulation, and secretion. This study aims to define the genetic aetiology and clinical phenotypes of PNDM in a large Egyptian cohort from a single centre.

METHODS

Patients with PNDM who were diagnosed, treated, or referred for follow-up between January 2002 and January 2021 were identified and clinically phenotyped. All patients were tested for mutations in EIF2AK3, KCNJ11, ABCC8, INS, FOXP3, GATA4, GATA6, GCK, GLIS3, HNF1B, IER3IP1, PDX1, PTF1A, NEUROD1, NEUROG3, NKX2-2, RFX6, SLC2A2, SLC19A2, STAT3, WFS1, ZFP57 using targeted next-generation sequencing (NGS) panel. INSR gene mutation was tested in one patient who showed clinical features of insulin resistance.

RESULTS

Twenty-nine patients from twenty-six families were diagnosed with PNDM. Pathogenic variants were identified in 17/29 patients (59%). EIF2AK3, INS, and K_ATP channel mutations were the commonest causes with frequency of 17%, 17%, and 14%, respectively. Patients with ABBC8 and KCNJ11 mutations were successfully shifted to sulfonylureas (SU). Paired data of glycosylated haemoglobin before and after SU transfer showed improved glycaemic control; 9.6% versus 7.1%, P = 0.041.

CONCLUSIONS

PNDM is a heterogenous disease with variable genotypes and clinical phenotypes among Egyptian patients. EIF2AK3, INS, ABCC8, and KCNJ11 mutations were the commonest causes of PNDM in the study cohort. All patients with K_ATP channel mutations were effectively treated with glyburide, reflecting the fact that genetic testing for patients with NDM is not only important for diagnosis but also for treatment plan and prognosis.

Long-term follow-up of a child with Wolcott-Rallison syndrome

Wolcott-Rallison syndrome (WRS), the most common cause of permanent neonatal diabetes mellitus (DM) in consanguineous families, has a poor prognosis, with a mean survival of 5.8 years. Majority of children with WRS succumb to the disease in the first decade of life. We present the long-term follow-up of an 8-year-2-month-old girl with genetically proven WRS who was born to a non-consanguineous parentage. She is on basal bolus regimen of insulin therapy for DM. In addition, she was noted to have features of skeletal dysplasia at 3 years and 3 months of age, which has led to her short stature. Surprisingly, she has had no episodes of hepatitis or liver dysfunction so far, which is frequently seen in children with WRS. To the best of our knowledge, she is the oldest surviving patient with WRS reported in India and South Asia.