Extensive Leukoencephalopathy in Spastic Paraplegia Type 4: Possible Role of Cerebral Autosomal Arteriopathy With Subcortical Infarcts and Leukoencephelopathy.

Despite recent advances in next-generation sequencing, the underlying etiology of adult-onset leukoencephalopathy has been difficult to elucidate. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a representative hereditary adult-onset leukoencephalopathy associated with vasculopathy. Leukoencephalopathy in spastic paraplegia type 4 (SPG4) is known to be rare, but it might be underestimated because most spastic paraplegia with leukoencephalopathy is rarely considered. We report a case of co-occurring SPG4 and CADASIL. A 61-year-old male presented with sudden visual impairment after a headache. He showed a spastic gait and had a family history with similar symptoms. An SPG4 gene mutation and a pathogenic variant in the NOTCH3 gene were found. This case shows that the diverse and complex clinical manifestations of patients with extensive leukoencephalopathy are related to more than one gene mutation. We also suggest the necessity for relevant genetic tests in the diagnosis of adult-onset leukoencephalopathy.