Prolonged Follow-Up in a 30-Year-Old Male With a Novel Pathogenic Variant in MSL3: A Case Report and a Brief Review of the Literature.

Basilicata-Akhtar syndrome (BAS) is an ultra-rare X-linked neurodevelopmental disorder caused by pathogenic variants in the MSL3 gene, critical for histone H4 acetylation and chromatin regulation. To date, only 42 cases have been documented, affecting both males and females, with most variants being de novo and loss-of-function. We present a case of a 30-year-old male with BAS, exhibiting developmental delay, intellectual disability, hypotonia, motor disturbances, and dysmorphic features. Genetic testing revealed a novel de novo hemizygous variant in the MSL3 gene (NM_078629:c.1293G > A, NP_523353.2:p.(Trp431*)), leading to loss of function. Neuroimaging showed multifocal leukoencephalopathy, and the individual is receiving treatment with carbidopa-levodopa with improvement in bradykinesia and camptocormia. This case expands our understanding of BAS and highlights the importance of genetic testing, especially Exome Sequencing (ES), in diagnosing rare conditions. Early diagnosis and multidisciplinary care are crucial for managing BAS and improving outcomes.