From Congenital Torticollis to Leigh Syndrome: A Case Report of Diagnostic Evolution in an Infant.

Leigh syndrome is a rare, progressive mitochondrial disorder of childhood. Early diagnosis is often challenging due to nonspecific clinical manifestations. We report a 1-month-old male infant initially referred for suspected congenital muscular torticollis who ultimately received a diagnosis of Leigh syndrome. Despite unremarkable perinatal history, he subsequently developed persistent feeding difficulties, recurrent vomiting, failure to thrive, and global developmental delay. Early neurological assessment revealed poor repertoire patterns on General Movement Assessment. The Neonatal Oral-Motor Assessment Scale (NOMAS) demonstrated dysfunctional oral-motor control, whereas the video fluoroscopic swallowing study (VFSS) revealed aspiration during swallowing. Brain MRI revealed symmetric basal ganglia lesions. Expanded whole-exome sequencing identified a pathogenic MT-ATP6 m.8993T>G variant with high heteroplasmy level (>90% in blood), confirming the diagnosis of Leigh syndrome. The variant was maternally inherited, although neither the mother nor the older sibling exhibited clinical features of mitochondrial disease. Leigh syndrome can initially manifest with subtle systemic features rather than overt neurological features. Persistent feeding difficulties and growth delay in infancy warrant thorough evaluation, including neuroimaging and comprehensive genomic testing, to enable timely diagnosis and optimize clinical management.