Spinal muscular atrophy is a medical condition that results in the weakening of muscles. The type of the condition depends on the age at which the disorder sets in. The most severe spinal muscular atrophy is Type 0, which is rare and often fatal.

Here are the different types of spinal muscular atrophy:

• Type 1 or Werdnig-Hoffman disease
  It is a common type of SMA and is diagnosed before the baby turns six months old. Babies with this type of SMA face multiple difficulties, such as muscle weakness, coughing, and trouble in breathing and swallowing. The babies may require feeding tubes and breathing assistance, and if not treated properly, it may be fatal.
• Type 2 or Dubowitz disease
  The symptoms of this kind of SMA appear between six months and two years from the birth of the baby. The first signs of this type of SMA are the delayed motor skills or the baby completely missing the milestones. Patients may be able to sit up but would need assistance. However, they lose their ability to walk and require wheelchairs.
• Type 3 or Kugelberg-Welander disease
  Type 3 is also known as juvenile disease and is diagnosed when the child is between 18 months to three years. Sometimes, it may be diagnosed when the child is in their teens. The affected child does not lose their ability to walk initially, but as they grow older, there may be more restrictions on their mobility. The patient may eventually need a wheelchair to move around.
• Type 4 or adult SMA
  Of the different types of SMA, this is extremely rare and surfaces during adulthood. Although the symptoms may appear at the age of 18 years, they usually commence after the person is 35 years old. This type of SMA leads to mild motor impairment, and the patient may be able to move and walk without difficulties for the remainder of their lives.
• Spinal Muscular Atrophy Respiratory Distress (SMARD)
  It is an extremely uncommon form of Type 1 SMA and primarily affects the upper part of the spinal cord. Babies may have severe respiratory distress and weakness in the arms and the surrounding area. SMARD is often diagnosed with genetic testing, and this disorder is primarily the result of a specific mutation.
• Distal SMA
  This is another uncommon type of the different types of SMA and may be inherited by the child from one of the parents. The weakness caused by distal SMA affects the feet and hands of the patients.
• Kennedy’s disease
  It is an X-genetic disorder, which is also very rare and affects only men. The onset may occur when the male is between 30 and 50 years of age. Kennedy’s disease causes atrophy (wasting) and muscle weakening in the entire body. However, the most visible effects are in the arms and legs. The symptoms are also visible in the throat and face and result in swallowing difficulties and affect the speech. They may also cause severe muscle cramping.