COMLEX USMLE Board Review Blogger

During the health supervision visit of a 10-year-old boy, you note some wasting and weakness of his lower leg muscles, with diminished patellar and ankle reflexes. You examine his parents’ legs and feet and notice that his mother has a bilateral foot drop and deformed feet.

Of the following, the MOST likely diagnosis is

a) Becker muscular dystrophy

b) celiac disease

c) chronic inflammatory demyelinating polyneuropathy

d) hereditary sensorimotor neuropathy

e) hydrocephalus

————————————————————————————————————————————–

• The child described in the vignette has physical findings suggestive of a chronic neuropathy. The distal weakness accompanied by reduced reflexes and loss of muscle bulk noted in the motor examination localize the problem to the peripheral nervous system. The presence of similar but more advanced symptoms in the mother (deformed foot with "hammer toes" – high-arched, flexed toes) supports a diagnosis of autosomal dominant hereditary sensorimotor neuropathy (eg, Charcot Marie Tooth disease). A large number of genes and loci have been identified for various forms of hereditary sensorimotor neuropathy. Referral to a neurologist, particularly one specializing in neuromuscular diseases, is recommended.
• Neuropathy may occur as part of more than 400 heritable diseases affecting peripheral nerve axons, myelin, or both. The most common primary, heritable forms are the hereditary sensorimotor neuropathies. Diagnostic evaluation is based on history and clinical findings, associated neurologic and systemic signs and symptoms, and results of clinical neurophysiologic studies (electromyography/nerve conduction velocities) that may localize the problem more accurately. Neuropathy also can be acquired. Autoimmune diseases, heavy metals and other toxins, chemotherapeutic and other medications, vitamin deficiencies (B₁, B₆, B₁₂, E), and endocrine disorders such as diabetes may damage peripheral nerves.
• Becker muscular dystrophy results in muscle weakness, but it is not associated with reduced muscle bulk and hyporeflexia. Additionally, Becker muscular dystrophy is caused by mutations in the dystrophin gene, and the pattern of inheritance is X-linked recessive, so the mother would not be symptomatic.
  Celiac disease can present with a variety of neuropathic problems, but both hands and feet are involved, pain in hands and feet often is prominent, and sensory ataxia might be present on physical examination. The prevalence in first-degree relatives is low.
• Chronic inflammatory demyelinating polyneuropathy (CIDP) usually occurs as an adverse long-term outcome of Guillain-Barré syndrome, also known as acute inflammatory demyelinating polyneuropathy (AIDP). The absence of a prior history of AIDP and the apparent autosomal dominant inheritance through the mother in this case make CIDP unlikely.
• Hydrocephalus can cause leg weakness due to compression of cortical spinal tract fibers to the legs, but the neurologic examination would document increased, not decreased reflexes.