Symptoms

The journey to a diagnosis for a child is usually triggered by a parent or healthcare professional.

In the more severe early onset form, SMA type 1 (non-sitters), parents and carers usually become worried about their infant’s floppiness (low muscle tone) and difficulty achieving physical milestones. Low muscle tone affects their child’s leg muscles more than their arms. It is also common for an infant to have feeding difficulties due to their weak swallowing muscles. Similarly, they often have breathing problems due to their weak breathing muscles.

Children with SMA type 2 (sitters), though not as severely affected as those with SMA type 1, also show signs of having muscle weakness in their legs more than their arms. Their swallowing and breathing muscles may or may not show signs of being affected.

Children with SMA type 3 (walkers) also show symptoms of leg rather than arm weakness. As their swallowing and breathing muscles are not usually affected, they do not tend to have swallowing and breathing symptoms.

Adults with adult onset SMA type 4 (walkers) usually experience first symptoms of muscle discomfort and/or pain. As their swallowing and breathing muscles are not usually affected, they do not usually have swallowing and breathing symptoms.