A Young Man With Distal Leg Wasting and Normal Sensation
An 18-year-old Black man presented with a 5-year history of limping and difficulty walking and going upstairs. He denied pain, numbness, cramps, fasciculations, or difficulties swallowing. His family and social histories were negative.
On examination he had normal mentation and cranial nerves. He had thin muscles, particularly in the distal legs with marked atrophy of the posterior compartment, but his feet muscles appeared normal, as did his upper extremities ( Fig. 82-1 ). Muscle strength testing revealed that his neck flexors, shoulder adductors, and elbow flexors and extensors were 4/5; wrist extensors and flexors were 4−/5. Interossei muscles were 5/5. Hip extension and flexion were 4−/5, knee extension and knee flexion were 3+/5, and feet flexors were 3/5; feet dorsiflexion was 4/5, eversion and inversion were 5/5. Feet muscles were normal. Reflexes were normal, except for trace ankle jerks. Sensation and coordination were normal. No fasciculations or myotonia was detected. The examination was otherwise normal.
Fig. 82-1
Patient showing prominent calf muscle atrophy.
What is the Most Likely Diagnosis?
The distal more than proximal weakness suggests a neuropathy, but he had normal sensation and relatively preserved reflexes. A hereditary motor sensory neuropathy such as Charcot–Marie–Tooth disease does manifest with distal leg weakness and atrophy and minimal sensory abnormalities initially; however, reflexes are diminished in those, particularly in the demyelinating type, and patients usually have weakness and atrophy of the feet muscles with high arches and hammertoes. Other predominantly motor neuropathies, such as those caused by porphyria and lead intoxication, are considerations, but the chronicity of symptoms and distribution of findings are against those. Patients with distal spinal muscular atrophy could have a similar presentation but usually are areflexic and have fasciculations. His presentation was rather suggestive of distal myopathy, particularly because of the atrophic legs with normal feet, sensation, and reflexes.
What Should Be Done Next?s
Serum creatine kinase (CK) level was 28,867 IU/L (normal, <210 IU/L); aspartate transaminase 270 IU/L (normal, 0–43 IU/L); alanine transaminase 228 IU/L (normal, 0–45 IU/L); l -lactate dehydrogenase 917 IU/L (normal, 100–270 IU/L); FANA, T4, and thyroid-stimulating hormone were normal.
