What are the other Names for this Condition? (Also known as/Synonyms)
- Congenital Insensitivity to Pain and Anhidrosis (CIPA)
- HSNIV (Hereditary Sensory Neuropathy Type IV)
- Nishida Syndrome
What is Hereditary Sensory Neuropathy Type IV? (Definition/Background Information)
- Hereditary Sensory Neuropathy Type IV (HSNIV) is a rare genetic condition, resulting in the loss of nerve function, leading to an inability to feel pain or sweat
- Individuals with HSNIV experience sensory nerve irregularities (sensory neuropathy), reduced ability to feel hot or cold, and reduced ability to feel pain. They may also develop varying degrees of intellectual disability
- The affected individuals are also at risk of developing painless injuries, due to a loss of sensation, leading to delayed wound healing. These include mild infections, sores on the feet and hands, or broken bones that may go unnoticed
- Hereditary Sensory Neuropathy Type IV is caused by a mutation in the NTRK1gene. The condition is inherited in an autosomal recessive manner. There is currently no known cure or method of prevention for HSNIV
- The disorder can be managed symptomatically to alleviate pain and stress. Active research is underway to develop treatments for HSNIV. But, typically, individuals with Hereditary Sensory Neuropathy Type IV have shortened life expectancies
Who gets Hereditary Sensory Neuropathy Type IV? (Age and Sex Distribution)
- Hereditary Sensory Neuropathy Type IV is a rare congenital disorder with an unknown prevalence. The condition is manifested in newborn children, and generally the signs and symptoms appear in the first few years of life
- HSNIV affects both males and females and no gender preference is noted
- Certain ethnicities, such as individuals of Japanese or Israeli Bedouin descent, have a greater risk for developing HSNIV
What are the Risk Factors for Hereditary Sensory Neuropathy Type IV? (Predisposing Factors)
- The risk factor for Hereditary Sensory Neuropathy Type IV is inheritance of a mutation from both of the parents (recessive pattern of inheritance)
It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.
Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.
What are the Causes of Hereditary Sensory Neuropathy Type IV? (Etiology)
The cause of Hereditary Sensory Neuropathy Type IV is a mutation in the NTRK1gene. It is inherited as an autosomal recessive trait
- NTRK1 encodes for the protein called neurotrophic tyrosine kinase receptor. This protein is essential for cell differentiation into sensory neurons. Mutations in NTRK1 do not create viable protein, preventing the formation of sensory neurons
- Two copies of the mutation (recessive) are necessary to produce signs and symptoms of HSN1V. If the mother and father are both carriers of the mutation, then a child will have a 25% chance of having HSNIV
Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).
What are the Signs and Symptoms of Hereditary Sensory Neuropathy Type IV?
The signs and symptoms due to Hereditary Sensory Neuropathy Type IV vary from individual to individual. Some have mild symptoms, whereas others may have severe symptoms.
Common signs and symptoms of Hereditary Sensory Neuropathy Type IV include:
- Inability to feel pain, touch, or temperature
- Inability to sweat (anhidrosis)
- Intellectual disabilities such as hyperactivity and emotional changes
- Open sores and unintentional self-injury on the hands and feet
- Bone fractures and recurrent joint dislocation
- Low muscle tone
The signs and symptoms of HSNIV typically appear within the first few months of life; but, in some cases, may not appear until late childhood.
How is Hereditary Sensory Neuropathy Type IV Diagnosed?
A diagnosis of Hereditary Sensory Neuropathy Type IV may involve:
- A complete physical examination for the signs and symptoms of HSNIV and a screening of the patient’s medical history
- A screening of a family medical history, to see if family member or relatives have HSNIV
- Genetic testing to determine if the NTRK1 gene is mutated
- Skin tests to detect abnormalities in sweat production
- Pain and temperature tests
- Nerve conduction studies: Neurological testing to test nerve conductance in order to determine the extent of neuropathy
Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.
What are the possible Complications of Hereditary Sensory Neuropathy Type IV?
Hereditary Sensory Neuropathy Type IV is an irreversible disorder. Complications of HSNIV that can occur include:
- Infection of open sores, resulting in limb amputation
- Self mutilation, resulting in unrecognized damage to the body
- Repeated injury, leading to the formation of Charcot joints (destroyed bone and tissue surrounding joints)
- Hyperthermia or hypothermia due to the inability to sweat
How is Hereditary Sensory Neuropathy Type IV Treated?
Currently, there is no cure for Hereditary Sensory Neuropathy Type IV. Relief from pain, symptoms, and stress of the disorder can be sought through the following treatment measures:
- Monitoring body temperature to manage hyperthermia or hypothermia
- Avoiding hot or cold environments
- Limiting activities to prevent injury
- Daily inspection of limbs for open sores or injury
- Tooth extraction to prevent self mutilation
- Antiseptic treatment to clean infections of open wounds
- Routine visits to surgeons, neurologists, dentists, and physiotherapists
How can Hereditary Sensory Neuropathy Type IV be Prevented?
- Currently, there are no specific methods or guidelines to prevent Hereditary Sensory Neuropathy Type IV, since it is a genetic condition
- Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
- If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
- Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as Hereditary Sensory Neuropathy Type IV
Regular medical screening at periodic intervals with tests, scans, and physical examinations are mandatory.
What is the Prognosis for Hereditary Sensory Neuropathy Type IV? (Outcomes/Resolutions)
- There is currently no known cure for Hereditary Sensory Neuropathy Type IV
- The life expectancy of an individual with HSNIV is variable. It depends on how well the symptoms are managed, but usually results in a shortened life span
- In general, the prognosis depends on the severity of the signs and symptoms
Additional and Relevant Useful Information for Hereditary Sensory Neuropathy Type IV:
Although there is currently no cure for Hereditary Sensory Neuropathy Type IV, research is actively being done to determine methods to potentially limit the adverse effects of the mutations on neurons.
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