Background:

KIF1C (Kinesin Family Member 1C) variants have been associated with hereditary spastic paraplegia and spastic ataxia.
Case report:
We report fraternal twins presenting with cerebellar ataxia and dystonic tremor. Their brain MRI showed a hypomyelinating leukoencephalopathy. Whole exome sequencing identified a homozygous KIF1C variant in both patients.
Discussion:

KIF1C variants can manifest as a complex movement disorder with cerebellar ataxia and dystonic tremor. KIF1C variants may also cause a hypomyelinating leukoencephalopathy.