Hypomyelination Leukodystrophy Type 11 (HLD11) Presenting with Diabetes: A Case Report and Literature Review.

Hypomyelination leukodystrophies (HLDs) are a group of rare genetic disorders that impair myelin formation in the central nervous system (CNS), leading to developmental delays and neurological symptoms. HLD type 11 (HLD11) is caused by mutations in the POLR1C gene, manifesting with a 4H phenotype (hypomyelination, hypodontia, and hypogonadotropic hypogonadism) and associated neurodevelopmental delays. Here, we report a case of a male patient diagnosed with HLD11 who presented with developmental delay, hypotonia, and cerebellar atrophy. Whole exome sequencing identified a homozygous likely pathogenic POLR1C variant. Notably, the patient developed diabetes, an association not previously documented in HLD11. Despite intensive care, he ultimately passed away due to complications at 3.5 years of age. This report highlights the importance of thorough endocrinological evaluation in HLD patients and underscores the need for further research to understand the full spectrum of HLD11 manifestations.