Differential Diagnosis for Teenage Male with Lower Extremity Weakness
Single Most Likely Diagnosis
- Muscular Dystrophy: This is a group of inherited disorders characterized by progressive muscle weakness and degeneration. Given the year-long history of lower extremity weakness in a teenage male, muscular dystrophy, particularly Duchenne or Becker muscular dystrophy, is a strong consideration due to its prevalence and the age of onset.
Other Likely Diagnoses
- Spinal Muscular Atrophy (SMA): SMA is a genetic disorder that affects the nerve cells responsible for controlling voluntary muscle movement. It could present with progressive weakness, especially in the lower extremities, although it typically starts earlier in life.
- Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): This is an autoimmune disorder where the body's immune system mistakenly attacks part of its peripheral nervous system, leading to nerve damage and muscle weakness. It can present at any age and might cause lower extremity weakness.
- Lyme Disease: If the patient lives in an area where Lyme disease is common, this infection could be a cause of lower extremity weakness due to its potential to cause neurological manifestations, including neuropathy.
Do Not Miss Diagnoses
- Spinal Cord Tumors or Compression: Tumors or other forms of compression on the spinal cord can cause progressive lower extremity weakness. Early diagnosis is crucial for treatment and preventing further neurological damage.
- Guillain-Barré Syndrome: Although typically presenting with a more acute onset, Guillain-Barré Syndrome is an autoimmune disorder that can cause rapid-onset muscle weakness. It's essential to consider due to its potential for respiratory failure and the need for urgent treatment.
- Vitamin Deficiencies (e.g., Vitamin B12 Deficiency): Certain vitamin deficiencies can lead to neurological symptoms, including weakness. These are important to identify as they are treatable.
Rare Diagnoses
- Mitochondrial Myopathies: These are a group of disorders caused by mitochondrial dysfunction, affecting muscle cells and leading to weakness among other symptoms. They are rare and might present with a variety of systemic symptoms in addition to muscle weakness.
- Inclusion Body Myositis: This is the most common acquired myopathy in adults over 50 but can occur in younger individuals. It causes progressive muscle weakness, typically affecting the lower extremities.
- Neuromuscular Junction Disorders (e.g., Myasthenia Gravis): While more commonly associated with fluctuating weakness and specific patterns of muscle involvement, these disorders could potentially present with lower extremity weakness in a teenage male, albeit rarely.