Proximal Hereditary Motor Neuropathy Type I (HMN-P prevalent in Finland), also known as distal hereditary motor neuropathy type VI (dHMN-VI), is a rare genetic disorder that affects the peripheral nervous system, specifically the motor neurons. This condition is characterized by progressive muscle weakness and wasting, particularly in the lower limbs.
Individuals with Proximal HMN-P typically develop symptoms during adolescence or early adulthood. The hallmark feature of this disorder is the selective involvement of motor neurons in the proximal regions of the body, including the upper arms and legs. This leads to difficulties in walking, running, and performing other activities that require the use of these muscles.
The underlying cause of Proximal HMN-P is a mutation in the gene called TRPV4 (transient receptor potential vanilloid 4), which is responsible for encoding a protein involved in the regulation of ion channels. The specific genetic mutation disrupts the normal functioning of this protein, leading to the degeneration and death of motor neurons.
Currently, there is no cure for Proximal HMN-P, and treatment focuses on managing symptoms and providing supportive care. This may involve physical therapy to maintain muscle strength and mobility, assistive devices to aid in walking and other daily activities, and medications to alleviate pain and discomfort.
Genetic counseling is recommended for individuals affected by Proximal HMN-P and their families, as the condition follows an autosomal dominant inheritance pattern. This means that affected individuals have a 50% chance of passing on the mutated gene to each of their children.
