What neurological disorder is characterized by progressive weakness that typically begins in infancy?

Spinal muscular atrophy (SMA) is a genetic disorder that is characterized by progressive weakness starting in infancy. This condition affects motor neurons located in the spinal cord, leading to muscle atrophy and weakness. SMA is caused by a mutation in the SMN1 gene, which results in insufficient protein production necessary for motor neuron health.

The hallmark of SMA is the early onset of symptoms, which often manifest as reduced muscle tone (hypotonia), difficulty in feeding, and delayed motor milestones. Infants may show weakness in the proximal muscles before the distal muscles, making it difficult for them to sit or crawl independently. The progressive nature of the weakness can lead to significant disability.

In contrast, myasthenia gravis typically presents later in life and is characterized by muscle weakness that fluctuates, often worsening with activity due to the underlying autoimmune mechanism affecting the neuromuscular junction. Cerebral palsy, on the other hand, is a group of disorders caused by brain injury or malformation occurring before, during, or shortly after birth, and while it involves motor impairments, it does not typically demonstrate the same pattern of progressive weakness seen in SMA. Multiple sclerosis is a demyelinating disorder that usually presents in young adulthood and involves a