Hereditary motor and sensory neuropathy with proximal dominance
Hereditary motor and sensory neuropathy with proximal dominance | |
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Synonyms | Hereditary motor and sensory neuropathy, Okinawa type |
Pronounce | |
Field | Neurology |
Symptoms | Muscle weakness, involuntary contractions, asthenia, muscle atrophy, sensory loss, urinary incontinence, chronic cough |
Complications | Progressive motor disability, severe sensory loss |
Onset | Typically begins in the fourth decade of life (40s) |
Duration | Chronic and progressive |
Types | |
Causes | Mutation in the TFG gene (chromosome 3q13.2) |
Risks | Family history, genetic inheritance |
Diagnosis | Electromyography, nerve conduction study, genetic testing, muscle biopsy |
Differential diagnosis | Amyotrophic lateral sclerosis, other motor neuron diseases, Charcot–Marie–Tooth disease |
Prevention | None known |
Treatment | Supportive therapy, physical therapy, symptom management |
Medication | Muscle relaxants, antispasmodics, pain management |
Prognosis | Slowly progressive; variable severity |
Frequency | Rare; mostly identified in families from Okinawa, Japan and Brazil |
Deaths | Variable, typically due to complications in late-stage disease |
Hereditary motor and sensory neuropathy with proximal dominance (HMSN-P), also known as Hereditary motor and sensory neuropathy, Okinawa type, is a rare neurodegenerative disorder characterized by progressive muscle weakness, involuntary contractions, and loss of sensation. It is inherited in an autosomal dominant pattern and typically begins in the fourth decade of life.
Presentation[edit | edit source]
HMSN-P manifests with:
- Involuntary and spontaneous muscle contractions
- Asthenia (loss of strength)
- Proximal muscle atrophy followed by distal sensory loss
- Spasms and fasciculations, particularly in early stages
- Urinary incontinence and chronic dry cough in some cases
The disease has clinical overlap with amyotrophic lateral sclerosis (ALS), including similar neuropathological findings, such as TDP-43-positive cytoplasmic inclusions in motor neurons.
Genetics and Pathophysiology[edit | edit source]
HMSN-P is caused by mutations in the TFG (tropomyosin-receptor kinase fused gene) located on chromosome 3q13.2. The mutation affects intracellular protein trafficking and is believed to play a role in the degeneration of motor neurons through disruption of the ubiquitin-proteasome pathway.
Pathological findings include:
- TFG/ubiquitin and/or TDP-43-positive cytoplasmic inclusions in spinal motor neurons
- Cytosolic aggregation of TDP-43 in cultured cells expressing mutant TFG
Diagnosis[edit | edit source]
Diagnosis involves a combination of:
- Clinical evaluation
- Electromyography (EMG)
- Nerve conduction studies
- Muscle biopsy
- Confirmatory genetic testing for mutations in the TFG gene
Treatment[edit | edit source]
There is no known cure for HMSN-P. Management is supportive and may include:
- Physical therapy to maintain mobility
- Assistive devices for ambulation
- Medications to control spasticity or pain
- Monitoring for urinary dysfunction
Prognosis[edit | edit source]
HMSN-P is slowly progressive. Disease severity and rate of progression vary among individuals. Although it is disabling, life expectancy may not be significantly reduced in all patients.
Epidemiology[edit | edit source]
HMSN-P is extremely rare. It has been described primarily in two large families from Okinawa, Japan. Cases have also been reported in descendants in Brazil, indicating a founder effect in these regions.
See also[edit | edit source]
External links[edit | edit source]
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Contributors: Prab R. Tumpati, MD