A form of axonal Charcot-Marie-Tooth disease, a peripheral sensorimotor neuropathy with symmetric weakness primarily occurring in the lower limbs and reaching the arms only after 5 to 10 years, occasional and predominantly distal sensory loss and reduced tendon reflexes. Presents with gait anomaly between the first and sixth decade and early onset is generally associated to a more severe phenotype that may include foot drop.

Ataxia with oculomotor apraxia type 2 (AOA2) is characterized by onset of ataxia between age three and 30 years after initial normal development, axonal sensorimotor neuropathy, oculomotor apraxia, cerebellar atrophy, and elevated serum concentration of alpha-fetoprotein (AFP).

Distal hereditary motor neuronopathy (dHMN or HMN) is a heterogeneous group of neuromuscular disorders caused by anterior horn cell degeneration and characterized by progressive distal motor weakness and muscular atrophy of the peripheral nervous system without sensory impairment. Distal HMN is also referred to as spinal Charcot-Marie-Tooth disease (spinal CMT). Distal HMN is often referred to as a 'neuronopathy' instead of a 'neuropathy' based on the hypothesis that the primary pathologic process resides in the neuron cell body and not in the axons (Irobi et al., 2006). Historically, Harding (1993) proposed a clinical classification of distal HMN into 7 phenotypic subtypes according to age at onset, mode of inheritance, and presence of additional features; see NOMENCLATURE. Genetic Heterogeneity of Autosomal Dominant Distal Hereditary Motor Neuronopathy Genetically distinct forms of autosomal dominant distal hereditary motor neuropathy include HMND1; HMND2 (158590), caused by mutation in the HSPB8 gene (608014); HMND3 (608634), caused by mutation in the HSPB1 gene (602195); HMND4 (613376), caused by mutation in the HSPB3 gene (604624); HMND5 (600794), caused by mutation in the GARS gene (600287); HMND6 (615575), caused by mutation in the FBXO38 gene (608533); HMND7 (158580), caused by mutation in the SLC5A7 gene (608761); HMND8 (600175), caused by mutation in the TRPV4 gene (605427); HMND9 (617721), caused by mutation in the WARS gene (191050); HMND10 (620080), caused by mutation in the EMILIN1 gene (130660); HMND11 (620528), caused by mutation in the SPTAN1 gene (182810); HMND12 (614751), caused by mutation in the REEP1 gene (609139); HMND13 (619112), caused by mutation in the BSCL2 gene (606158); and HMND14 (607641), caused by mutation in the DCTN1 gene (601143). See also X-linked HMN (HMNX; 300489), caused by mutation in the ATP7A gene (300011) on chromosome Xq21. Additional disorders with overlapping features include autosomal dominant ALS4 (602433), caused by mutation in the SETX gene (608465); and CMS7A (616040), caused by mutation in the SYT2 gene (600104).

Syndrome with characteristics of seizures, sensorineural deafness, ataxia, intellectual deficit, and electrolyte imbalance. It has been described in five patients from four families. The disease is caused by homozygous or compound heterozygous mutations in the KCNJ10 gene, encoding a potassium channel expressed in the brain, spinal cord, inner ear and kidneys. Transmission is autosomal recessive.

SPTLC1-related hereditary sensory neuropathy (HSN) is an axonal form of hereditary motor and sensory neuropathy distinguished by prominent early sensory loss and later positive sensory phenomena including dysesthesia and characteristic "lightning" or "shooting" pains. Loss of sensation can lead to painless injuries, which, if unrecognized, result in slow wound healing and subsequent osteomyelitis requiring distal amputations. Motor involvement is present in all advanced cases and can be severe. After age 20 years, the distal wasting and weakness may involve proximal muscles, possibly leading to wheelchair dependency by the seventh or eighth decade. Sensorineural hearing loss is variable.