A 1-year-old girl has not achieved typical motor milestones and has weak muscle tone. She also has difficulty feeding and has failed to gain weight appropriately. On physical examination, there is profound muscle weakness and decreased deep tendon reflexes. What might be the diagnosis and what are the next steps?
The girl's symptoms of delayed motor milestones, weak muscle tone (hypotonia), feeding difficulties, and failure to thrive suggest a condition called spinal muscular atrophy (SMA), an autosomal recessive genetic disorder characterized by loss of motor neurons and progressive muscle wasting. The next steps would involve genetic testing for deletions or mutations in the SMN1 gene to confirm the diagnosis. Management would involve a multidisciplinary team approach including physical and occupational therapy, nutritional support, and possibly newly emerging gene therapies.