Abstract
Neurofibromatosis is a genetically transmitted illness that affects the nervous system as well as tissues such as bones and skin. The transmission of neurofibromatosis occurs in an autosomal dominant manner where an affected parent conveys the faulty genes to his progeny. Therefore, having a family history of neurofibromatosis elevates the risk of developing the condition. Genetic tests can help determine one’s chances of having the disease and passing it to his or her children. The condition often results in the growth of tumors on the nerves. There are three forms of neurofibromatosis (type 1, type 2 neurofibromatosis and schwannomatosis) and each form has distinctive traits. In the United States, it is projected that one out of every 3,000 people has this condition. Though neurofibromatosis cannot be completely cured, there are options that can alleviate some of the symptoms associated with the condition. These options include radiation therapy and surgical procedures. Chemotherapeutic agents are not frequently used in the management of neurofibromatosis notwithstanding the numerous clinical trials that have been undertaken. Therefore, there is a need to carry out additional research on chemotherapeutic agents to diversify the range of treatment options in the management of neurofibromatosis.
Introduction
Neurofibromatosis (NF) is a genetically transmitted illness that affects the nervous system particularly the brain and the spinal cord (Tonsgard, 2006). The transmission of neurofibromatosis occurs in an autosomal dominant manner. The condition has an effect on the formation and development of the nerve cells and may result in growth of tumors on the nerves. The tumors, which are also referred to as neurofibromas, may be benign, but on rare occasions they may turn out to be cancerous. There are three forms of neurofibromatosis, which are type 1 neurofibromatosis (NF1), type 2 neurofibromatosis (NF2, bilateral acoustic neurofibromatosis or Von Recklinghausen’s disease) and schwannomatosis (Neurofibromatosis, 2007). NF1 often begins during childhood and leads to alterations on the skin and bone deformation. Individuals with this form of neurofibromatosis are often born with the disease symptoms. Type 2 neurofibromatosis leads to the impairment of hearing ability, a buzzing reverberation in the ears and a poor sense of balance.
Causes of Neurofibromatosis
Neurofibromatosis occurs as a result of hereditary or spontaneous alterations in the genetic constituents of an individual (Tonsgard, 2006). In approximately half of all neurofibromatosis instances, a parent transmits the faulty NF gene to his or her progeny leading to an autosomal dominant conduction. On rare occasions, the erasure of the NF1 or NF2 gene may lead to the development of neurofibromatosis. The NF1 gene is hypothesized to have tumor-suppressor activities caused by the secretion of a compound known as neurofibromin. Therefore, anything that affects this gene usually increases the probability of developing cancers (Rasmussen, Young & Friedman, 2001). A spontaneous genetic mutation that happens without any specific cause may also cause neurofibromatosis. The mutation usually occurs on the 17th chromosome of the NF1 gene (Williams et al., 2009). In such cases, the person involved usually does not have any inherited association or a family history of neurofibromatosis. However, such mutations are maintained in the individual’s genetic makeup and can still be transmitted to the individual’s offspring.
Symptoms
The diagnosis of neurofibromatosis relies heavily on the symptoms displayed by a patient. Therefore, it is imperative that a health care provider carefully observes the indicators of the condition. The symptoms observed vary with the type of neurofibromatosis. In NF1, for instance, the initial signs include the presence of numerous skin lacerations, which are also referred to as ‘café au lait’ marks (Hersh & The Committee on Genetics, 2008). These spots happen anywhere on the body and are more pronounced during infancy. It is thought that approximately a tenth of normal healthy babies are born with café au lait marks. Gentle tumors start growing on the surface of the skin, beneath the surface of the skin and within the nerve tissues in puberty (Hersh & The Committee on Genetics, 2008). In 2% to 5% of these instances, the lumps initiate pain and become malignant. In addition, distinctive bony abrasions known as “pseudarthrosis, sphenoid wing hypoplasia, an optic glioma, 2 or more iris Lisch nodules” (Tonsgard, 2006, p.2) are also seen.
Other symptoms shown in NF1 include lightheadedness, bulging and malformation of the bones, hearing loss, and a reduced capability to learn new things. The spine may curve leading to a condition known as scoliosis. In addition, swelling of the optic nerve (optic gliomas) can also lead to blurred eyesight (Hersh & The Committee on Genetics, 2008). Cardiovascular complications such as vasculopathy, congenital heart problems and high blood pressure may also accompany NF1 and are the key causes of death related to NF1 (Williams et al., 2009).
In NF2, a large proportion of patients develop tumors on the eighth cranial nerve (the vestibulocochlear nerve), which innervates the ears. The eighth cranial nerve consists of two portions that carry our distinct functions. The first section of this nerve, which is the acoustic nerve, relays signals concerning sound in the direction of the brain thereby aiding in hearing. The second section of this nerve is the vestibular nerve, which transmits information regarding the sense of balance to the brain. The initial symptoms of NF2 affect both sections of the eighth cranial nerve leading to their dysfunction. The dysfunction manifests as tinnitus (a buzzing reverberation in the ears) and imbalance (Neurofibromatosis, 2007). Tumors may also develop on other nerves apart from the cranial nerves. These other tumors stem from the Schwann cells and are called schwannomas (Ferner et al., 2007). Schwann cells form a shielding layer around nerves and provide electric protection that is requisite during transmission of information. Therefore, the indicators associated with schwannomas are determined by their location. For example, numbness of a given body region may arise if schwannomas develop on nerve cells that depart from the spinal cord around that particular region. For instance, a hand may feel numb if schwannomas develop on the nerves that depart from the spinal cord around the hand region. Weakness and lack of sensation in the legs may be experienced in cases where large tumors press against the spinal cord. Some people with NF2 may develop cataracts, which may lead to eye complications.
In the third type of neurofibromatosis (schwannomatosis), the key symptom is immense persistent pain that can crop up in any section of the body. In roughly a third of schwannomatosis patients, the pain dominates a specific section of the body such as one arm or leg (Ferner et al., 2007).
Treatment
Neurofibromatosis does not have a permanent cure because the reason for its development is present in the genetic makeup of an individual. However, there exist medications that can help in the management the symptoms of neurofibromatosis. The choice of medication utilized is determined by the type of the disease as well as its level of progression and may include treatment with radioactive radiation, drugs and surgical procedures to get rid of the tumors.
In NF2, for example, the only accessible remedy alternatives are surgical and radiation treatments. However, the nature and location of the tumors (near sensitive and delicate nerves) make surgical procedures extremely risky endeavors since there is an immense danger of damaging the delicate nerves leading to additional neurological complications. Radiation therapy is usually regarded as the next treatment alternative in instances where the position and extent of the tumor rule out surgery. In this process, the tumors are exposed to high-energy x-rays, which cause the shrinkage of the malignant cells. However, radiation therapy also has its risks. Therefore, it is imperative to ensure that the potential benefits of radiotherapy outweigh the risks before embarking on the procedure.
The occurrence of cutaneous and subcutaneous neurofibromas may have adverse consequences on an individual’s aesthetics thereby causing psychosocial disturbances to patients and their family members. Therefore, counseling and support groups are essential in assisting such people to deal with the disease.
Experiments involving mice show that a drug called lovastatin overturns the cognitive effects linked with neurofibromatosis type 1 (Williams et al., 2009). It is thought that the drug lowers the abnormally elevated quantities of p21/Ras, which is a chemical compound that functions in the biochemical path that plays a significant pathophysiologic function in the cognitive outcomes witnessed in NF1 (Williams et al., 2009). Tumor cells in neurofibromatosis can be targeted by the administration of tipifarnib and rapamycin (Williams et al., 2009). Substances with antihistamine activities such as Ketotifen fumarate are sometimes used in the management of plexiform neurofibromas because they are thought to suppress the production of mast cells, which are presumed to influence the growth of the neurofibromas (Williams et al., 2009). However, attempts to manage neurofibromatosis focus more on radiation therapy and surgery than on drugs. Therefore, some of the mentioned drugs are still undergoing clinical trials as their overall efficacy still remains unknown.
Prevention
There is no known technique that can be used to prevent neurofibromatosis since it is an inherited condition that can also occur through spontaneous mutations of one’s genes. The only possible solution to lower its prevalence rates is for people who have a history of the condition in their families to undertake genetic testing and psychotherapy. These procedures are useful in determining whether such people can pass on the risk of developing neurofibromatosis to their progeny. In addition, the genetic tests reveal the probability of such people having the disease and ensure that diagnoses are made early enough to avert future complications.
Prognosis
A large percentage of people with NF2 experience the initial symptoms (poor hearing and imbalance) between their late teens and early twenties. A small fraction of these patients may develop signs of neurofibromatosis in their infancy while others do not manifest any symptoms until they reach their 50’s. These symptoms may be experienced for protracted periods before the actual nature of the complications is recognized since malignancies take time to develop.
Generally, NF1 is a progressive condition implying that most signs deteriorate in due course even though a few people may display constant symptoms. Therefore, foreseeing the direction of a person’s condition is not feasible. On the whole, most NF1 patients develop mild to modest symptoms and have a typical life expectancy. However, tumors growing on or beneath the surface of the skin usually tend to increase as one matures and may bring about aesthetic and psychological concerns. In addition, malignant tumors in NF1 are known to lower life expectancy by approximately fifteen years (Rasmussen et al., 2001). Prompt diagnosis and treatment of the condition reduce mortality rates significantly.
NF2, on the other hand, may be serious as it may lead to the destruction of the surrounding important structures, for instance, the brainstem as well as other cranial nerves. A large proportion of persons with schwannomatosis experience immense pain, which in certain extreme instances is relentless and may immobilize these people.
Incidence of Neurofibromatosis in the United States
Approximately 100,000 people are affected by neurofibromatosis in the United States annually (Ferner et al., 2007). NF1 is a relatively common condition, and it is estimated that one in every 3,000 people has the condition (Rasmussen et al., 2001). This incidence rate translates to 90,066 cases annually, which is about 0.03% of the entire U.S. population (Statistics about neurofibromatosis, 2013).
Conclusion
Neurofibromatosis is an inherent condition that one has no control over. It increases one’s chances of developing cancers due to the role of the NF1 and N2 genes in the suppression of cancer. Neurofibromatosis lowers the quality of life. It may cause deaths and reduce one’s life expectancy. However, it is possible to reduce the number of deaths caused by neurofibromatosis by undergoing genetic tests to determine one’s chances of developing the condition. It is also important to establish any history of the disease in one’s family to determine the chances of transmitting the condition to one’s offspring. Research needs to be done to diversify the treatment options for the condition since the commonly available options focus more on radiation and surgical procedures than the use of drugs.
References
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Hersh, J. H. & The Committee on Genetics. (2008). Health supervision for children with neurofibromatosis. Pediatrics, 121(3), 633-642.
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Rasmussen, S. A., Young, Q., & Friedman, J. M. (2001). Mortality in neurofibromatosis 1: An analysis using U.S. death certificates. The American Journal of Human Genetics, 68(5), 1110-1118.
Statistics about neurofibromatosis. (2013). Web.
Tonsgard, J. H. (2006). Clinical manifestations and management of neurofibromatosis type 1. Seminars in Pediatric Neurology, 13(1), 2-7.
Williams, V. C., Lucas, J., Babcock, M. A., Gutmann, D. H., Korf, B., & Bernard L. Maria, B. L. (2009). Neurofibromatosis type 1 revisited. Pediatrics, 123(1), 124-133.