Diagnosis of the Day – 16
IC/CC: A 3 year-old boy is brought to the pediatrician by his parents because he
has been having trouble getting up from a sitting or lying position, although he
had previously done so with ease.
HPI: His developmental history is notable for delayed motor skills; he began
walking at 18 months. The boy has a waddling gait, and when sitting, he uses his
arms to push himself into the upright position. The boy’s maternal uncle, who
died at age 16, suffered from similar symptoms when he was younger.
PE: VS: BP = 116/68, HR = 96, RR = 19, Temp = 37.2 C. Physical exam reveals
marked muscle weakness of the extremities, particularly of the proximal muscle
groups, and hypertrophy of the calf muscles.
Labs: WBC: normal.
Questions
1. What are “motor skills”?
2. What is the significance of having a maternal uncle who suffered similar
symptoms?
3. Are any of the vital signs abnormal? Do younger children (2-3 years old)
have higher or lower resting heart rates and respiratory rates?
4. How does the calf muscle appear when there is hypertrophy?
5. If this patient had a muscular disease that causes destruction of all muscle
fibers throughout the body, would you expect this patient to have a normal
lifespan? (explain your answer)
6. If this disease was caused by a chromosome defect on the mother’s X-gene,
and she was a carrier of the trait, and the parents had a second son, what are
the odds that the second son would develop this disease as well?
7. What is the name of this genetic disease causing destruction of muscles?
Muscular Dystrophy
Muscular dystrophies are genetic disorders characterized by progressive muscle wasting and weakness that
begin with microscopic changes in the muscle. As muscles degenerate over time, the person’s muscle
strength declines.
In Duchenne Muscular Dystrophy, boys begin to show signs of muscle weakness as early as age 3. The
disease gradually weakens the skeletal, or voluntary, muscles, those in the arms, legs and trunk. By the early
teens or even earlier, the boy’s heart and respiratory muscles also may be affected.
Becker Muscular Dystrophy is a much milder version of DMD. Its onset is usually in the teens or early
adulthood, and the course is slower and far less predictable than that of DMD.
Duchenne Muscular Dystrophy occurs when a particular gene on the X chromosome fails to make the
protein dystrophin. Becker Muscular Dystrophy results from different mutations in the same gene. People
with BMD have some dystrophin, but it’s not enough or it’s poor in quality. Having some dystrophin
protects the muscles of those with Becker from degenerating as badly or as quickly as those of people with
Duchenne.
The course of Duchenne Muscular Dystrophy is fairly predictable. Children with the disorder are often late
in learning to walk. In toddlers, parents may notice enlarged calf muscles, or pseudohypertrophy.
A preschooler with DMD may seem clumsy and fall often. Parents also may note that he has trouble
climbing stairs, getting up from the floor or running.
By school age, the child may walk on his toes or the balls of his feet, with a slightly rolling gait. He has a
waddling and unsteady gait and can easily fall over. To try to keep his balance, he sticks his belly out and
puts his shoulders back. He also has difficulty raising his arms.
Many children with DMD lose the ability to walk some time between ages 7 and 12.
Pseudohypertrophy of calf: fatty tissue accumulation on biopsy