We describe siblings born from non-consanguineous parents, with older sibling having asymptomatic hyperglycaemia while younger sibling presented with low birth weight and persistent hyperglycaemia from first month of life. Our case, the older sibling was heterozygous for paternally inherited GCK pathogenic variant resulting in diabetes of maturity-onset in the young (MODY) manifested as mild fasting hyperglycaemia. GCK gene sequencing revealed that the younger sibling was compound heterozygous for missense mutations (two) combined in a novel GCK-permanent neonatal diabetes mellitus (PNDM) genotype. Thus, heterozygous inactivating GCK mutations are likely to lead to maturity-onset diabetes of the young type 2 (MODY 2) and the homozygous inactivating or compound heterozygous GCK mutations are a cause of PNDM.
- genetic screening / counselling
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Contributors All the listed authors CMO, MBK, VK and AK played a role in the clinical management, planning, execution, analysis, writing of the manuscript and that they all agree and accept responsibility for the contents of the manuscript submitted to BMJ Case Reports.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.