The severe disorders associated with KIF16B-pathogenesis constitute phenotypic features such as global developmental delay (GDD), severe intellectual disability, microcephaly, hypotonia and facial dysmorphism. Brain magnetic resonance imaging (MRI) showed diffuse white matter volume loss in the centrum semiovale, corona radiata regions with ex vacuo dilation of the lateral ventricles and diffuse thinning of the corpus callosum. Electroencephalography (EEG) showed continuous spike, polyspike, and wave epileptic discharges in the bilateral occipital head region, which were maximal in the right hemisphere. However, nerve conduction tests was normal.
Table 1: Growth parameters for the 2 affected individuals.
| Feature | Patient 1 | Patient 2 |
| Age | 6 years | 2 years |
| Weight | 17 kg (5th percentile) | 11 kg (5th-10th percentile) |
| Head circumference | 47 cm (<1st percentile) | 44.5 cm (<1st percentile) |
| Height | 105 cm (2nd percentile) | 82 cm (5th-10th percentile) |