MedGen

Autosomal recessive distal hereditary motor neuronopathy-9 (HMNR9) is a slowly progressive peripheral neuropathy characterized by juvenile onset of distal muscle weakness and atrophy, resulting in gait difficulties. Most affected individuals also have upper limb involvement with weakness and atrophy of the hand muscles. Foot deformities are often present. Some patients may have mild sensory abnormalities or pyramidal signs. Electrophysiologic studies are consistent with a length-dependent axonal motor neuropathy (summary by Jacquier et al., 2023). For a discussion of genetic heterogeneity of autosomal recessive HMN, see HMNR1 (604320). [from OMIM]

Primary coenzyme Q10 (CoQ10) deficiency is usually associated with multisystem involvement, including neurologic manifestations such as fatal neonatal encephalopathy with hypotonia; a late-onset slowly progressive multiple-system atrophy-like phenotype (neurodegeneration with autonomic failure and various combinations of parkinsonism and cerebellar ataxia, and pyramidal dysfunction); and dystonia, spasticity, seizures, and intellectual disability. Steroid-resistant nephrotic syndrome (SRNS), the hallmark renal manifestation, is often the initial manifestation either as isolated renal involvement that progresses to end-stage renal disease (ESRD), or associated with encephalopathy (seizures, stroke-like episodes, severe neurologic impairment) resulting in early death. Hypertrophic cardiomyopathy (HCM), retinopathy or optic atrophy, and sensorineural hearing loss can also be seen. [from GeneReviews]