What Is HSAN-3?
HSAN-3 is a type of CMT caused by autosomal recessive mutations in the ELP1 gene. This gene provides instructions for making a component of the elongator complex, which is important for the development and survival of nerve cells, particularly those of the autonomic and sensory nervous systems. Mutations in the ELP1 gene disrupt this function, leading to impaired nerve signal transmission.
HSAN-3 is autosomal recessive, meaning that both copies of the gene must have a mutation to cause this subtype.
Clinical Features
Symptoms of HSAN-3 are present from birth and primarily affect the autonomic and sensory nervous systems. This subtype is characterized by widespread autonomic dysfunction alongside reduced pain and temperature sensation. Nerve conduction studies usually show somewhat slowed conduction velocities and reduced amplitudes, consistent with an axonal form of CMT.
HSAN-3 symptoms may include:
- Absence of overflow tears when crying
- Unstable blood pressure and heart rate
- Autonomic crises, including episodes of vomiting
- Reduced pain and temperature sensation
- Reduced or absent reflexes
- Poor coordination and unsteady gait
- Difficulty feeding and swallowing, particularly in infancy
- Foot drop
- Additional symptoms not listed here
Disease Course
HSAN-3 is a disease present from birth that requires lifelong management. Autonomic crises, blood pressure instability, and difficulty with feeding and swallowing are significant sources of morbidity, particularly in infancy and childhood. With careful management of autonomic and respiratory complications, many individuals survive into adulthood, though the disease course remains variable and serious.
