VPS13D-related disorders presenting as a pure and complicated form of hereditary spastic paraplegia

Alterations of vacuolar protein sorting-associated protein 13 (VPS13) family members including VPS13A, VPS13B, and VPS13C lead to chorea acanthocytosis, Cohen syndrome, and parkinsonism, respectively. Recently, VPS13D mutations were identified as a cause of VPS13D-related movement disorders, which show several phenotypes including chorea, dystonia, spastic ataxia, and spastic paraplegia.

We applied whole-exome analysis for a patient with a complicated form of hereditary spastic paraplegia (HSP) and her unaffected parents. Then, we screened the candidate genes in 664 Japanese families with HSP in Japan.

We first found a compound heterozygote VPS13D mutation and a heterozygote ABHD4 variation in a sporadic patient with spastic paraplegia. Then, we found three patients with VPS13D mutations in two Japanese HSP families. The three patients with homozygous mutations (p.Thr1118Met/p.Thr1118Met and p.Thr2945Ala/p.Thr2945Ala) in the VPS13D showed an adult onset pure form of HSP. Meanwhile, the patient with a compound heterozygous mutation (p.Ser405Arg/p.Arg3141Ter) in the VPS13D showed a childhood onset complicated form of HSP associated with cerebellar ataxia, cervical dystonia, cataracts, and chorioretinal dystrophy.

In the present study, we found four patients in three Japanese families with novel VPS13D mutations, which may broaden the clinical and genetic findings for VPS13D-related disorders.