NKX6-2 Disease in Two Unrelated Patients with Early-Onset Spastic Quadriplegia and Diffuse Hypomyelinating Leukodystrophy

•Spastic ataxia type 8 (NKX6-2 related disorder) presents with hypomyelinating leukodystrophy.•Pathogenic biallelic variants in NKX6-2 gene are responsible for the disease.•Two phenotypes have been described including the neonatal/ early onset and the late onset form with variable degree of severity.•Brain MRI is a helpful part of the diagnostic workup but not specific.•Targeted or comprehensive genetic testing is a crucial part of the diagnostic workup.