Friedreich's ataxia

Friedreich's ataxia is an inherited disease that causes progressive damage to the nervous system resulting in symptoms ranging from gait disturbance and speech problems to heart disease. It is named after the German physician Nicholaus Friedreich, who first described the condition in the 1860s. "Ataxia," which refers to coordination problems such as clumsy or awkward movements and unsteadiness, occurs in many different diseases and conditions. The ataxia of Friedreich's ataxia results from the degeneration of nerve tissue in the spinal cord and of nerves that control muscle movement in the arms and legs. The spinal cord becomes thinner and nerve cells lose some of their myelin sheath the insular covering on all nerve cells that helps conduct nerve impulses.

Friedreich's ataxia, although rare, is the most prevalent inherited ataxia, affecting about 1 in every 50,000 people in the United States. Males and females are affected equally.

Friedreich's ataxia is an autosomal recessive congenital ataxia and is caused by a mutation in Gene X25 that codes for frataxin, located on chromosome 9. This protein is essential in neuronal and muscle cells for proper functioning mitochondria and the mutation causes inadequate production of frataxin. This results in, among other things, a degeneration of nerve tissue in the spinal cord.

Delatycki et al. (2000) provided an overview of the clinical features, pathology, molecular genetics, and possible therapeutic options in Friedreich ataxia.

Friedreich's ataxia and muscular dystrophy, though often compared, are completely different diseases. Muscular dystrophy is the result of muscle tissue degeneration whereas Friedreich's ataxia is the result of nervous tissue degeneration caused by a trinucleotide repeat expansion mutation. Both are researched by the Muscular Dystrophy Association.

There are two types, the classic form and one in association with a genetic vitamin E deficiency. They cannot be distinguished clinically.

Symptoms
Symptoms begin sometime between the ages of 5 to 15 years and include any combination, but not necessarily all of the following:

it presents before 25 years of age with progressive staggering gait, frequent falling and titubation. lowerextremities are more severly involved.
 * Muscle weakness in the arms and legs
 * Loss of coordination
 * Vision impairment
 * Hearing loss
 * Slurred speech
 * Curvature of the spine (scoliosis)
 * Carbohydrate intolerance
 * Extreme heart conditions (e.g., atrial fibrillation, and resultant tachycardia (fast heart rate) and cardiomyopathy (enlargement of the heart))

These symptoms are slow and progressive. Long-term observation shows that many patients reach a plateau in symptoms in the patient's early adulthood. Because of many of these symptoms, a person suffering from Friedrich's Ataxia may require some surgical interventions (mainly for the spine and heart). Often a metal rod is inserted in the spine to help prevent or slow the progression of scoliosis. As progression occurs, assistive devices such as a cane or walker or a wheelchair are required for mobility (independence).

SIGNS

nystagmus, fast saccadic eye movements, truncal titubation, dysarthria, dysmetria, absent deep tendon reflexes, extensor plantar responses, weakness which is greater distally are commonly found.loss of vibratory and proprioceptive sensation occurs. median age of death is 35 years, females have far better prognosis with 20year survival being 100% as compared to 63% in men. cardiac involvment occurs in 90%of patients. cardiomegaly, symmetrical hypertrophy, murmurs, conduction defects. 20% cases are found in association with diabetes mellitus type 1 or 2 or pancreatic β cell dysfunction. PATHOGENESIS

primary site of pathology is spinal cord and peripheral nerves.sclerosis and degeneration of spinocerebellar tracts, lateral corticospinal tracts, and posterior columns. in peripheral nerves there is a loss of large myelinated fibres.

GENETICS

Classic form has been mapped to 9q13-q21, and mutant gene contains expanded GAA triplet repeats in the first intron of "frataxin gene".

Treatment
Up until recently, possibly due to a lack of understanding of what caused the lack of protein production, treatment has been focused on addressing the symptoms. On August 20th 2006, research findings circulated in Nature Chemical Biology which showed that compounds they developed could reactivate the defective gene in white blood cell samples and restore some level of the protein production. The scientists indicate if progress continues as expected, drugs for human sampling may be available around spring of 2008.