A 10-year-old boy apparently normal at bih had delayed walking and had difficulty in walking. As years passed, weakness increased and now is wheelchair bound. What is your diagnosis
**Core Concept**
Spinal muscular atrophy (SMA) is a genetic disorder characterized by the degeneration of spinal motor neurons, leading to progressive muscle weakness and wasting. It is caused by a deficiency of the survival motor neuron (SMN) protein, which is essential for motor neuron survival and function.
**Why the Correct Answer is Right**
The patient's symptoms of delayed walking, progressive muscle weakness, and eventual wheelchair-bound status are classic features of spinal muscular atrophy. The disease is typically caused by a deletion or mutation in the SMN1 gene, leading to a deficiency of the SMN protein. This deficiency results in the degeneration of spinal motor neurons, which in turn causes muscle weakness and wasting. The disease is usually inherited in an autosomal recessive pattern, meaning that both parents are carriers of the mutated gene.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify a genetic disorder, which is the underlying cause of spinal muscular atrophy.
* **Option B:** This option is incorrect because it suggests a muscular dystrophy, which is a group of genetic disorders that affect muscle strength and function, but does not accurately describe spinal muscular atrophy.
* **Option C:** This option is incorrect because it suggests a peripheral neuropathy, which is a condition that affects the nerves outside the brain and spinal cord, but does not accurately describe the degeneration of spinal motor neurons in spinal muscular atrophy.
**Clinical Pearl / High-Yield Fact**
Spinal muscular atrophy is a genetic disorder that can be diagnosed through genetic testing, including PCR and sequencing of the SMN1 gene. Early diagnosis and treatment with antisense oligonucleotides, such as nusinersen, can improve muscle strength and function in patients with spinal muscular atrophy.
**Correct Answer: C. Spinal muscular atrophy**