New genetic causes for complex hereditary spastic paraplegia.

Introduction: Hereditary Spastic Paraplegia (HSP) represents a complex and heterogeneous group of rare neurodegenerative disorders that share a common clinical feature of weakness and lower limb spasticity that can occur alone or in combination with a constellation of other neurological or systemic signs and symptoms. Although the core clinical feature of weakness and lower limb spasticity is virtually universal, the genetic heterogeneity is almost uncountable with more than 70 genetic forms described so far. We performed review of medical records from twenty-one patients from seventeen Brazilian families with complex phenotype of HSP. All cases have previously negative mutations in SPG11/KIAA1840 and SPG7 gene and were evaluated by whole-exome sequencing. An extensive description of systemic and neurological signs has been described.

Results: Whole-exome sequencing was unremarkable in eight patients and established a definite genetic diagnosis in thirteen patients of twelve non-related families. Mutations were found in genes previously implicated in other neurodegenerative disorders such as Amyotrophic Lateral Sclerosis, Hereditary Neuropathy, Spastic Ataxias, Neurodegeneration with Brain Iron Accumulation, Glycogen Metabolism, Congenital Lipodystrophy and aminoacyl-tRNA synthetases disorders.

Conclusions: We report thirteen new genetically-proven cases of complex HSP, expanding the clinical spectrum of presentations of HSP, providing new pathophysiological mechanisms and disclosing new potential therapeutic targets.