SMA or spinal muscular atrophy is an inherited condition, which affects only one in 6000-10,000 people. When someone suffers from SMA, they lose control over their muscle movements. Usually, people with SMA undergo a gene mutation. The symptoms, onset, as well as, the progression of SMA vary from one person to another. Here, we’ll discuss with you some rare types of spinal muscle atrophy. 

Rare types of SMA
The rare types of spinal muscle atrophy are usually caused as a result of gene mutation. Typically, there are three rare types of SMA. These include:

1. SMARD
   Spinal muscular atrophy with respiratory distress is a rare type of SMA and is primarily caused by the mutation of the IGHMBP2 gene. This SMA is predominantly diagnosed in infants and leads to severe breathing problems in them. Some of the early warning signs of SMARD include noisy and difficult breathing, pneumonia that relapses frequently, inability to take the feed, and a feeble cry. Infants between the age of six weeks to six months will undergo a sudden incapacity to breathe because of paralysis of the muscles, which separate the diaphragm and the abdomen. SMARD is inherited in what is called the autosomal recessive pattern. So, the parents of the child with SMARD carry a copy of the mutated gene. However, neither of them display any sign of the condition.
2. SBMA
   SBMA or spinal-bulbar muscular atrophy, also known as Kennedy’s disease, is another rare type of SMA. It is predominantly seen in younger adults between the ages of 20-40 years. Some common symptoms experienced in this type of SMA include weakness in the limbs, tremors of hands, twitching, and muscle cramps. At times, it may also cause infertility in some men. Though it can lead to the inability to walk in the later stages in life, this type of spinal muscle atrophy wouldn’t do anything to your life expectancy. This is predominantly a disorder of nerve cells (that start at the spinal cord or the part of the brain, which is connected to the spinal cord), which controls the motor neurons. This SMA is extremely rare in women as well as men, as it is found in only one out of 1,50,000 males.
3. Distal SMA
   Lastly, we have distal SMA. It develops as a result of the mutations in one of the many genes, such as  GARS, DYNC1H1,  and  UBA1.  As a result of this type of SMA, the nerve cells present in the spinal cord are affected. The symptoms of Distal SMA begin when the child is in his adolescence. During this time, the primary symptoms experienced include wasting of the limb muscles and the cramps. However, this type of SMA will not alter the life expectancy of an individual, and it has a relatively slower progression.