Spinal muscular atrophy (SMA) is a genetic neuromuscular disease. SMA patients have either a missing or altered gene, (the survival motor neuron-1 or SMN1 gene), which causes large motor nerves of the spine to become abnormal, according to Move Forward.
When a patient shows symptoms of SMA, a blood test is able to indicate 95 percent of cases by identifying the genetic mutation from which the disease originates. However, 5 percent of cases are caused by a different, rarer mutation that can only be discovered through other tests.
This is the most common strain of the disease. This strain can be identified from birth or in the first six months of a child’s life, if the child doesn’t learn to sit in a controlled manner. The child in question presents severely weak muscles and muscle tone. Symptoms include atrophy (muscle wasting), decreased movement and weak muscles in the head, arms, necks, legs and torso. There is also the possibility of developing respiratory infections, hand tremors and hand spasms.
In type 2, the disease typically develops between the first six and 18 months of life. The weakness caused by type 2 is less severe than in type 1, as children can sit and stand but may not be capable of walking unassisted. Spasms and tremors are less common, however tightening of the joints is a frequent symptom. As in type 1, there is also the possibility of developing respiratory infections. Breathing assistance is sometimes needed in the later stages of the disease.
Type 3 develops later in life, as it’s usually discovered between the ages of 18 months and three years, and holds a better prognosis. Children develop more normally and can sometimes manage to walk independently. Walking ability is often maintained until later in childhood or adolescence. However, there’s often problems with balance, falling, scoliosis, and a greater knee extension which causes the knee joint to bend back. The weakness is mainly centred around the muscles in the hips, manifesting less severely than in the other types.
There are some other types of spinal muscular atrophy caused by a rarer gene. These variations of the disease include distal spinal muscular atrophy, Kennedy disease, and others.
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