<unk>  (MMA), is a rare motor neuron disease first described in 1959 in Japan. Its symptoms usually appear about two years after adolescent growth spurt and is significantly more common in males (average age of onset, 15- to 25-year-old). MMA is reported most frequently in Asia but has a global distribution. It is typically marked by insidious onset of muscle atrophy of an upper limb, which plateaus after two to five years from which it neither improves nor worsens. There is no pain or sensory loss associated with MMA. MMA is not believed to be hereditary. Both the names for the disorder and its possible causes have been evolving since first reported in 1959. It is most commonly believed the condition occurs by asymmetrical compression of the cervical spinal column by the cervical dural sac, especially when the neck is flexed. However, the disease is uncommon and diagnosis is confused by several atypical reports.
Monomelic amyotrophy
Congenital distal spinal muscular atrophy
Chondrodystrophy
Spinal muscular atrophy with lower extremity predominance 1
Hereditary neuralgic amyotrophy
Spinal muscular atrophy
Congenital muscular dystrophy
Spinal and bulbar muscular atrophy