Infantile spinal muscular atrophy

My report is on Infantile Spinal Muscular Atrophy. I chose this disorder because I had a family member who was diagnosed and died from it. I wanted to learn more about the disease. Spinal Muscular Atrophies (SMA) are inherited disorders. Spinal muscular atrophy, as defined by international criteria, requires the weakness to be symmetrical and greater in the proximal muscles than in the distal ones. (5) It is when nerves fail to function normally and the muscle cells with which they are connected deteriorate. SMA is when muscles weaken and waste away from degeneration or motor neurons (1). It is a progressive, symmetrical muscle weakness which usually presents itself within the first six months of life. Death usually occurs between six and twenty months, either of respiratory failure or secondary to chest infection (3). There are different forms according to age of onset the forms include: Infantile SMA- Type 1 SMA or Werdnig-Hoffman disease (0-6 mos.) Intermediate SMA- Type 2 SMA (7-18 mos.) Juvenile SMA-Type3 or Kugelberg-Welander disease (18 mos.>) Adult onset SMA -Type 4 SMA

      Infantile SMA is the most severe form some of the symptoms include:  muscle weakness, poor muscle tone, weak cry, limpness or a tendency to flop, difficulty sucking or swallowing, and accumulation of secretions in the lungs or throat.  The legs tend to be weaker than the arms, Feeding difficulties, increased susceptibility to respiratory tract infections, developmental milestones, such as lifting the head or sitting up, can't be reached (2).  The earlier the symptoms appear the shorter the life span.  The onset is sudden and dramatic. Once the symptoms appear the child's cells quickly deteriorates shortly after.  My cousin (Kim) first noticed her baby's (Anthony) symptoms when he was a month old.  They were different then some of the other symptoms.  She noticed quivering of the tongue and heavy breathing.  The doctor had to do a muscle biopsy to diagnose. The disease is fatal there is no cure for SMA yet known.  The symptoms just get worse.  The major management issue in type 1 SMA   the prevention and early treatment of respiratory infections (4).Pneumonia is the cause of death in the majority of the cases.  Infants are already in a weakened and vulnerable state.  Infants will eventually require respiratory support and feeding tubes.  Parents can choose to withhold the respiratory support and nutritional support.  Infants with Type 1 have a life expectancy of less than two years.  Anthony's life expectance was six months.  Management of SMA is a huge medical expense.  At three months, his mother made a decision to put him feeding tubes, which she then had to be taught how to do the feedings at home.  At five months she had to make a decision on whether or not to put him on life support.  Because of his weak respiratory system, he would have frequent episodes of respiratory failure where he had to go to the hospital several times.  She made the decision not to put him on life support on account that he was all ready terminal.  Anthony died at the age of six months and three days.

In order to be diagnosed with SMA presentation of symptoms need to be present. A secure diagnosis should not be made without an adequate muscle biopsy. A muscle biopsy specimen processed with histochemical stains. The features will vary with the type of SMA correlates with the age of onset. A muscle biopsy however, does not provide a reliable indication of the future course of the patient. (7) Other diagnostic tests are the EMG (electromyography) and presentation of clinical symptoms. Also several exclusionary criteria must be met. Such as there should be no evidence of central nervous system damage, involvement of other neurological systems or other organs, sensory loss, eye muscle weakness, or significant facial weakness(6) SMA is caused by a faulty gene. In a new study in mice, scientists found that inserting extra copies of a specific gene helped the mice produce sufficient amounts of a protein called SMN (Survival Motor Neuron) low amounts of this protein cause SMA Type 1 SMA is the most common cause of genetically determined neonatal death, with an incidence of 1 in 25,708 live births. This translates to a gene frequency of about 1 in 160 and a carrier frequency of 1:80 (8) In 1978 Pearn Corporation published a series of papers on SMA. He reported that childhood onset SMA is not an uncommon disease and has an incidence in the range of 4 per 100,000, which makes it at least twice as common as Amyotrophic Lateral Sclerosis (ALS) a.k.a. Lou Gehrig's disease. He confirmed it is an autosomal recessive inheritance gene and defined the later-onset type as a more benign autosomal dominant gene(9). Spinal muscular atrophy is the second most common lethal, autosomal recessive disease in Caucasians (16). For SMA 1 it takes a recessive gene from both parents in order to have the disease, if both parents have the recessive gene, each baby has a 25% chance of having the illness. Each of their subsequent children have a 50% of carry the recessive gene. Couples need to have genetic counseling before deciding to have more children. Counseling is available to these families through the community. In 1990 mapping of the gene for SMA to chromosome 5q11.2-13.3 was reported and culminated in to a 3 year research by the Muscular Dystrophy Association (10). The findings were also confirmed by French researchers. The recent findings of SMA to autosomal recessive chromosome 5q has allowed for prenatal diagnosis. It is, however, too early to confirm the reliability of testing. Families who are at risk, or who have had a child with the diagnosis can have an amniocentesis done during pregnancy for DNA testing. It gathers information from a sample of your amniotic fluid that is the fluid that surrounds the baby in your uterus. This testing will tell you about your baby's health and development and will determine whether it has genetic or chromosomal abnormalities. Some women choose not to have this test taking due to that it has a risk of a miscarriage. It is must liking done the around 15 and 18 months of pregnancy. The accuracy of prenatal prediction has been calculated to be 88% to 99% depending on the individual family. Although gene replacement strategies are being tested in animals, current treatment for SMA consists of prevention and management of the secondary effect of chronic motor unit loss. It is likely that gene replacement for SMA will require many more years of investigation before it can be applied to humans (11). Due to the new age of molecular biology, there is a better understanding of the Spinal Muscular Atrophies. An international collaborative effort has narrowed the gene locus of SMA type 1 to a very small region on the short arm of chromosome 5, it is anticipated that the gene itself will be defined shortly. Once defined, the defective gene product will be studied and it's function explored to achieve a better understanding of it's pathology. This is the first step in devising effective treatment. The first effective specific treatment for SMA may be only a few years away.