All individuals had delayed milestones of motor development and muscular hypotonia. Six have never learned to walk without support, whereas the other six have an ataxic gait and are only able to walk short distances.
All patients (ten) bearing a de novo mutation within ATP binding motifs II and VI remained non-verbal, whereas two patients bearing the identical mutation (p.Arg493His) within RNA binding motif Ia speak 4 and 20 words, respectively.
Subtle and only partially overlapping facial dysmorphisms were observed.
Feeding difficulties were observed in nine, autistic features and sleep disturbances in seven, and strabismus and joint hypermobility in six individuals. Notably some patients were melatonin resistant regarding sleep disturbances.
Three patients developed seizures.
Unilateral cryptorchidism was observed in two out of four boys.
Brain anomalies on MRI were observed in nine individuals and included: delayed myelination, dilated ventricles, corpus callosum abnormalities, and cerebral or cerebellar atrophy.