Autosomal dominant distal hereditary motor neuropathy

Autosomal dominant distal hereditary motor neuropathy (also known as distal hereditary motor neuronopathy or dHMN) is a clinically and genetically heterogeneous group of rare inherited neurological disorders characterized by progressive weakness and wasting (atrophy) of muscles in the distal parts of the limbs, particularly the feet, legs, and hands. Unlike hereditary motor and sensory neuropathies (such as Charcot-Marie-Tooth disease), distal hereditary motor neuropathies predominantly affect motor neurons, with minimal or no sensory involvement. The condition primarily impacts the peripheral nervous system, specifically the lower motor neurons that control voluntary muscle movement. Symptoms typically begin with difficulty walking, foot drop, and weakness in the lower legs, often progressing to involve the hands and forearms. Foot deformities such as pes cavus (high-arched feet) and hammer toes are common. The age of onset is variable, ranging from childhood to adulthood depending on the specific genetic subtype. Progression is generally slow, and life expectancy is usually not significantly reduced, though disability can be substantial over time. Multiple genes have been implicated in autosomal dominant forms, including HSPB1, HSPB8, BSCL2, GARS1, DYNC1H1, and others, reflecting the genetic heterogeneity of this condition. There is currently no cure or disease-modifying treatment for autosomal dominant distal hereditary motor neuropathy. Management is supportive and symptomatic, including physical therapy to maintain muscle strength and flexibility, occupational therapy, orthotic devices (such as ankle-foot orthoses) to assist with walking, and surgical interventions for skeletal deformities when necessary. Genetic counseling is recommended for affected individuals and their families. Research into potential targeted therapies is ongoing.

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