Friedreich's ataxia is the most prevalent inherited ataxia, affecting about 1 in 50,000 people in the United States. Males and females are affected equally. The estimated carrier prevalence is 1:110.

A 1984 Canadian study was able to trace 40 cases of classical Friedreich's disease from 14 French-Canadian kindreds previously thought to be unrelated to one common ancestral couple arriving in New France in 1634: Jean Guyon and Mathurine Robin.

Friedreich's ataxia is an autosomal recessive inherited disease that causes progressive damage to the nervous system. It manifests in initial symptoms of poor coordination such as gait disturbance; it can also lead to scoliosis, heart disease and diabetes, but does not affect cognitive function. The disease is progressive, and ultimately a wheelchair is required for mobility. Its incidence in the general population is roughly 1 in 50,000.

The particular genetic mutation (expansion of an intronic GAA triplet repeat in the FXN gene) leads to reduced expression of the mitochondrial protein frataxin. Over time this deficiency causes the aforementioned damage, as well as frequent fatigue due to effects on cellular metabolism.

The ataxia of Friedreich's ataxia results from the degeneration of nervous tissue in the spinal cord, in particular sensory neurons essential (through connections with the cerebellum) for directing muscle movement of the arms and legs. The spinal cord becomes thinner and nerve cells lose some of their myelin sheath (the insulating covering on some nerve cells that helps conduct nerve impulses).

The condition is named after the German physician Nikolaus Friedreich, who first described it in the 1860s.

The importance of correctly recognizing progressive muscular atrophy as opposed to ALS is important for several reasons.

- 1) the prognosis is a little better. A recent study found the 5-year survival rate in PMA to be 33% (vs 20% in ALS) and the 10-year survival rate to be 12% (vs 6% in ALS).

- 2) Patients with PMA do not suffer from the cognitive change identified in certain groups of patients with MND.

- 3) Because PMA patients do not have UMN signs, they usually do not meet the "World Federation of Neurology El Escorial Research Criteria" for “Definite” or “Probable” ALS and so are ineligible to participate in the majority of clinical research trials such as drugs trials or brain scans.

- 4) Because of its rarity (even compared to ALS) and confusion about the condition, some insurance policies or local healthcare policies may not recognize PMA as being the life-changing illness that it is. In cases where being classified as being PMA rather than ALS is likely to restrict access to services, it may be preferable to be diagnosed as "slowly progressive ALS" or "lower motor neuron predominant" ALS.

An initial diagnosis of PMA could turn out to be slowly progressive ALS many years later, sometimes even decades after the initial diagnosis. The occurrence of upper motor neurone symptoms such as brisk reflexes, spasticity, or a Babinski sign would indicate a progression to ALS; the correct diagnosis is also occasionally made on autopsy.

The life expectancy of people with A-T is highly variable. The average is approximately 25 years, but continues to improve with advances in care. The two most common causes of death are chronic lung disease (about one-third of cases) and cancer (about one-third of cases).

People with A-T have a highly increased incidence (approximately 25% lifetime risk) of cancers, particularly lymphomas and leukemia, but other cancers can occur. When possible, treatment should avoid the use of radiation therapy and chemotherapy drugs that work in a way that is similar to radiation therapy (radiomimetic drugs), as these are particularly toxic for people with A-T. The special problems of managing cancer are sufficiently complicated that treatment should be done only in academic oncology centers and after consultation with physicians who have specific expertise in A-T. Unfortunately, there is no way to predict which individuals will develop cancer. Because leukemia and lymphomas differ from solid tumors in not progressing from solitary to metastatic stages, there is less need to diagnose them early in their appearance. Surveillance for leukemia and lymphoma is thus not helpful, other than considering cancer as a diagnostic possibility whenever possible symptoms of cancer (e.g. persistent swollen lymph glands, unexplained fever) arise.

Women who are A-T carriers (who have one mutated copy of the ATM gene), have approximately a two-fold increased risk for the development of breast cancer compared to the general population. This includes all mothers of A-T children and some female relatives. Current consensus is that special screening tests are not helpful, but all women should have routine cancer surveillance.

Progressive muscular atrophy (PMA), also known as Duchenne-Aran muscular atrophy and by various other names, is a rare subtype of motor neuron disease (MND) that affects only the lower motor neurons. PMA is thought to account for around 4% of all MND cases. This is in contrast to amyotrophic lateral sclerosis (ALS), the most common form of MND, which affects both the upper and lower motor neurones, or primary lateral sclerosis, another rare MND variant, which affects only the upper motor neurons. The distinction is important because PMA is associated with a better prognosis than classic ALS.

Toxic optic neuropathy refers to the ingestion of a toxin or an adverse drug reaction that results in vision loss from optic nerve damage. Patients may report either a sudden loss of vision in both eyes, in the setting of an acute intoxication, or an insidious asymmetric loss of vision from an adverse drug reaction. The most important aspect of treatment is recognition and drug withdrawal.

Among the many causes of TON, the top 10 toxins include:

- Medications

- Ethambutol, rifampin, isoniazid, streptomycin (tuberculosis treatment)

- Linezolid (taken for bacterial infections, including pneumonia)

- Chloramphenicol (taken for serious infections not helped by other antibiotics)

- Isoretinoin (taken for severe acne that fails to respond to other treatments)

- Ciclosporin (widely used immunosuppressant)

- Acute Toxins

- Methanol (component of some moonshine, and some cleaning products)

- Ethylene glycol (present in anti-freeze and hydraulic brake fluid)

Metabolic disorders may also cause this version of disease. Systemic problems such as diabetes mellitus, kidney failure, and thyroid disease can cause optic neuropathy, which is likely through buildup of toxic substances within the body. In most cases, the cause of the toxic neuropathy impairs the tissue’s vascular supply or metabolism. It remains unknown as to why certain agents are toxic to the optic nerve while others are not and why particularly the papillomacular bundle gets affected.

TAA is an old term for a constellation of elements that can lead to a mitochondrial optic neuropathy. The classic patient is a man with a history of heavy alcohol and tobacco consumption. Respectively, this combines nutritional mitochondrial impairment, from vitamin deficiencies (folate and B-12) classically seen in alcoholics, with tobacco-derived products, such as cyanide and ROS. It has been suggested that the additive effect of the cyanide toxicity, ROS, and deficiencies of thiamine, riboflavin, pyridoxine, and b12 result in TAA.

Roberts syndrome is an extremely rare condition that only affects about 150 reported individuals. Although there have been only about 150 reported cases, the affected group is quite diverse and spread worldwide. Parental consanguinity (parents are closely related) is common with this genetic disorder. The frequency of Roberts syndrome carriers is unknown.

At this time, there are no other phenotypes (observable expressions of a gene) that have been discovered for mutations in the ESCO2 gene.

Though there is no treatment for Cone dystrophy, certain supplements may help in delaying the progression of the disease.

The beta-carotenoids, lutein and zeaxanthin, have been evidenced to reduce the risk of developing age related macular degeneration (AMD), and may therefore provide similar benefits to Cone dystrophy sufferers.

Consuming omega-3 fatty acids (docosahexaenoic acid and eicosapentaenoic acid) has been correlated with a reduced progression of early AMD, and in conjunction with low glycemic index foods, with reduced progression of advanced AMD, and may therefore delay the progression of cone dystrophy.

FEVR is, as its name suggests,

familial and can be inherited in an

autosomal dominant, autosomal

recessive or X-linked recessive pattern.1-3 It is caused by mutations in

FZD4, LRP5, TSPAN12 and NDP

genes, which impact the wingless/

integrated (Wnt) receptor signaling

pathway. 3 Disruption of this path

way leads to abnormalities of vascu-

lar growth in the peripheral retina. 2,3

It is typically bilateral, but asymmetric, with varying degrees of

progression over the individual’s

lifetime. Age of onset varies, and

visual outcome can be strongly

influenced by this factor. Patients

with onset before age three have a

more guarded long-term prognosis

whereas those with later onset are

more likely to have asymmetric

presentation with deterioration of

vision in one eye only. 2-3 However,

because FEVR is a lifelong disease,

these patients are at risk even as

adults.2 Ocular findings and useful

vision typically remain stable if the

patient does not have deterioration

before age 20.2,4 Due to the variability and unpredictability of the

disease course, patients with FEVR

should be followed throughout

their lifetime.

Clinical presentation can vary

greatly. In mild variations, patients

may experience peripheral vascular

changes, such as peripheral avascular zone, vitreoretinal adhesions,

arteriovenous anastomoses and a

V-shaped area of retinochoroidal

degeneration. 4 Severe forms may

present with neovascularization,

subretinal and intraretinal hemorrhages and exudation. 4 Neovascularization is a poor prognostic

indicator and can lead to retinal

folds, macular ectopia and tractional retinal detachment. 2,4 Widefield FA has been crucial in

helping to understand this disease,

as well as helping to confirm the

diagnosis. An abrupt cessation

of the retinal capillary network

in a scalloped edge posterior to

fibrovascular proliferations can

be made using FA.2,3,5 Patients can

also show delayed transit filling on

FA as well as delayed/patchy choroidal filling, bulbous vascular terminals, capillary dropout, venous/venous shunting and abnormal

branching patterns. 2,3,5 The staging of FEVR is similar

to that of retinopathy of prematurity. The first two stages involve an

avascular retinal periphery with or

without extraretinal vascularization (stage 1 and 2, respectively). 4 Stages three through five delineate

levels of retinal detachment; stage 3

is subtotal without foveal involvement, stage 4 is subtotal with foveal

involvement and stage 5 is a total

detachment, open or closed funnel.4

Because there was neovascularization in the absence of retinal detachment, our patient was

considered to have

stage 2.

Familial exudative vitreoretinopathy (FEVR) ( ) is a genetic disorder affecting the growth and development of blood vessels in the retina of the eye. This disease can lead to visual impairment and sometimes complete blindness in one or both eyes. FEVR is characterized by exudative leakage and hemorrhage of the blood vessels in the retina, along with incomplete vascularization of the peripheral retina. The disease process can lead to retinal folds, tears, and detachments.

Familial transmission is now recognized in a small proportion of people with MacTel type 2; however, the nature of any related genetic defect or defects remains elusive. The MacTel genetic study team hopes that exome analysis in the affected population and relatives may be more successful in identifying related variants.

Although a variety of complex classification schemes are described in the literature, there are essentially two forms of macular telangiectasia: type 1 and type 2. Type 1 is typically unilateral and occurs almost exclusively in males after the age of 40.

Type 2 is mostly bilateral, occurs equally in males and females.

At least one type of autosomal dominant cone-rod dystrophy is caused by mutations in the guanylate cyclase 2D gene (GUCY2D) on chromosome 17.

Although cancer syndromes exhibit an increased risk of cancer, the risk varies. For some of these diseases, cancer is not their primary feature. The discussion here focuses on their association with an increased risk of cancer. This list is far from exhaustive.

A cancer syndrome or family cancer syndrome is a genetic disorder in which inherited genetic mutations in one or more genes predispose the affected individuals to the development of cancers and may also cause the early onset of these cancers. Cancer syndromes often show not only a high lifetime risk of developing cancer, but also the development of multiple independent primary tumors. Many of these syndromes are caused by mutations in tumor suppressor genes, genes that are involved in protecting the cell from turning cancerous. Other genes that may be affected are DNA repair genes, oncogenes and genes involved in the production of blood vessels (angiogenesis). Common examples of inherited cancer syndromes are hereditary breast-ovarian cancer syndrome and hereditary non-polyposis colon cancer (Lynch syndrome).

Many patients eventually develop acute myelogenous leukemia (AML). Older patients are extremely likely to develop head and neck, esophageal, gastrointestinal, vulvar and anal cancers. Patients who have had a successful bone marrow transplant and, thus, are cured of the blood problem associated with FA still must have regular examinations to watch for signs of cancer. Many patients do not reach adulthood.

The overarching medical challenge that Fanconi patients face is a failure of their bone marrow to produce blood cells. In addition, Fanconi patients normally are born with a variety of birth defects. A good number of Fanconi patients have kidney problems, trouble with their eyes, developmental retardation and other serious defects, such as microcephaly (small head).

Fanconi anaemia (FA) is a rare genetic disease resulting in impaired response to DNA damage. Although it is a very rare disorder, study of this and other bone marrow failure syndromes has improved scientific understanding of the mechanisms of normal bone marrow function and development of cancer. Among those affected, the majority develops cancer, most often acute myelogenous leukemia, and 90% develop bone marrow failure (the inability to produce blood cells) by age 40. About 60–75% of people have congenital defects, commonly short stature, abnormalities of the skin, arms, head, eyes, kidneys, and ears, and developmental disabilities. Around 75% of people have some form of endocrine problems, with varying degrees of severity.

FA is the result of a genetic defect in a cluster of proteins responsible for DNA repair.

Treatment with androgens and hematopoietic (blood cell) growth factors can help bone marrow failure temporarily, but the long-term treatment is bone marrow transplant if a donor is available. Because of the genetic defect in DNA repair, cells from people with FA are sensitive to drugs that treat cancer by DNA crosslinking, such as mitomycin C. The typical age of death was 30 years in 2000.

FA occurs in about one per 130,000 births, with a higher frequency in Ashkenazi Jews in Israel and Afrikaners in South Africa. The disease is named after the Swiss pediatrician who originally described this disorder, Guido Fanconi. It should not be confused with Fanconi syndrome, a kidney disorder also named after Fanconi.

The prognosis of patients with FA as a whole is considered to be better than that of most other forms of non-small cell carcinoma, including biphasic pulmonary blastoma.

FA is a rare tumor, with a relative incidence estimated to be no more than 0.5% of all lung cancers.

FA is exceptionally rare in children, with only a handful of cases reported to date, However, several case reports have involved FA's in pregnant women or the early postnatal period.

Genetic, environmental, hormonal, and immune-system factors have been shown to be involved in the manifestation of seborrhoeic dermatitis.

Seborrhoeic dermatitis may be aggravated by illness, psychological stress, fatigue, sleep deprivation, change of season and reduced general health.

In children, excessive vitamin A intake can cause seborrhoeic dermatitis. Lack of biotin, pyridoxine (vitamin B), or riboflavin (vitamin B) may be a cause in babies.

Those with immunodeficiency (especially infection with HIV) and with neurological disorders such as Parkinson's disease (for which the condition is an autonomic sign) and stroke are particularly prone to it.

Seborrhea affects 1 to 5% of the general population. It is slightly more common in men, but affected women tend to have more severe symptoms. The condition usually recurs throughout a person's lifetime. Seborrhea can occur in any age group but usually starts at puberty and peaks in incidence at around 40 years of age. It can reportedly affect as many as 31% of older people. Severity is worse in dry climates.

Bone marrow failure in both children and adults can be either inherited or acquired. Inherited bone marrow failure is often the cause in young children, while older children and adults may acquire the disease later in life. A maturation defect in genes is a common cause of inherited bone marrow failure. The most common cause of acquired bone marrow failure is aplastic anemia. Working with chemicals such as benzene could be a factor in causing the illness. Other factors include radiation or chemotherapy treatments, and immune system problems.