An eight-year-old boy who is falling frequently and has difficulty getting up from the floor I brought to see his pediatrician. His teacher is concerned about his learning abilities. Her mother says that he walked at 18 months and that there is no family history of neuromuscular disorders. He has a normal general physical examination, an exaggerated lumbar lordosis; tight heel cords, toe walking and needs to use his hands to get up from the floor. His muscle stretch reflexes are normal.

1) The differential diagnosis include all of the following except:

A. Spinal muscular atrophy (SMA)

B. Pompe disease (glycogenosis II)

C. Charcot-Marie-Tooth neuropathy

D. Duchenne muscular dystrophy

E Congenital Muscular dystrophy

2) The nerve conduction velocities are normal and the CK is 15,000 U/ML A test that is very specific and can confirm the diagnosis is:

1. Electromyography (EMG)
2. A muscle biopsy
3. A nerve biopsy
4. A skin biopsy
5. A mucosal rectal biopsy

3) A non-invasive test that can confirm the diagnosis in 65% of the patients is:

1. DNA test for SMA
2. Determination of acid maltase deficiency
3. DNA test for CMT1A
4. DNA test for merosin deficiency
5. DNA test for Duchenne muscular dystrophy

4) The lack of family history in hereditary disorders can be explained by:

A. New mutations

B. Paternity may be questionable

C. Some of the affected patients may be clinically asymptomatic

D. Autosomal recessive inheritance

E All of the above

Correct Answer: E