Two Sibling Cases of Spastic Paraplegia-45 with a Novel Pathogenic Variant in NT5C2 Gene: Concomitant RYR1 Gene in One Sibling

Introduction: Hereditary spastic paraplegia (SPG) is a genetically and clinically heterogeneous group of rare neurodegenerative disorders. SPG45 is the AR inherited type of complicated SPG, which is due to a mutation in the NT5C2 gene. Case Presentation: Two sisters, aged 8 and 4, exhibited delayed motor development since early childhood. They also experienced learning difficulties, dysarthric speech, ataxia, nystagmus, strabismus, and spasticity in their extremities. Additionally, brisk deep tendon reflexes were observed in their upper and lower limbs, and they exhibited positive pathological reflexes. Whole-exome sequencing identified a previously unidentified homozygous mutation in the NT5C2 gene, leading to the diagnosis of SPG45 in both siblings. A mutation in the RYR1 gene associated with malignant hyperthermia was also detected in one of the siblings, necessitating ongoing monitoring. Discussion/Conclusion: To the best of our knowledge, we report the first case of a patient with coexistence of the NT5C2 gene and the RYR1 gene.