Question 1

A mother presents to your pediatric office with her two-year-old son for his annual well-child exam. She states that her son did not begin walking until around the same time as her other children, at 16 months, however she has noticed that he often moves in a peculiar fashion. She states that when her son moves from sitting on the floor to standing, he awkwardly grasps and pulls on various body parts from the knees to hips until he is standing upright. What is the correct term to describe this movement and what does it suggest?

A) Gower's Sign, distal muscle weakness
B) Psoas Sign, proximal muscle weakness
C) Gower's Sign, proximal muscle weakness
D) Psoas Sign, distal muscle weakness

C
Explanation: Weakness in muscular dystrophy selectively affects the proximal before the distal limb muscles. It also affects the lower extremities before the upper extremities. The affected child often presents with difficulty running, jumping, and walking up steps. When arising from the floor, affected boys may also use hand support to push themselves to an upright position, an action termed "Gower's sign".

Accepted Answer

Weakness in muscular dystrophy selectively affects the proximal before the distal limb muscles. It also affects the lower extremities before the upper extremities. The affected child often presents with difficulty running, jumping, and walking up steps. When arising from the floor, affected boys may also use hand support to push themselves to an upright position, an action termed "Gower's sign".

Question 2

Which intracellular protein expressed in smooth, skeletal and cardiac muscle is entirely missing in Duchenne muscular dystrophy and reduced in Becker's muscular dystrophy?&#10;A) Myostatin&#10;B) Dystrophin&#10;C) Myogenin&#10;D) Casein

Accepted Answer

Dystrophin is located on the cytoplasmic face of the plasma membrane of muscle fibers, functioning as a component of a large, tightly associated glycoprotein complex. In its absence, the glycoprotein complex is digested by proteases. Loss of these membrane proteins may initiate the degeneration of muscle fibers, resulting in muscle weakness. In Duchenne muscular dystrophy, dystrophin is missing, while in Becker's muscular dystrophy its presence is reduced, but not missing entirely.

Question 3

A mother and father present with concerns regarding how their three-year-old son has been moving around the home. They state that when he is playing and chasing his seven-year-old sister, he often tires easily, walking on his tiptoes and moving in a waddling fashion, almost like a duck. They noticed it has been going on for the last 4-5 months and while they assumed he would grow out of it, it has persisted. You explain that you would like to run preliminary testing, as his symptoms and age align with potential muscular dystrophy. You describe his gait pattern to the parents and label it as:

A) Neuropathic gait
B) Myopathic gait
C) Choreiform gait
D) Ataxic gait

Accepted Answer

In muscular dystrophy, with bilateral weakness, you will have dropping of the pelvis on both sides during walking leading to a myopathic (or waddling gait). Neuropathic gait is seen in patients with foot drop (weakness of foot dorsiflexion), the cause of this gait is due to an attempt to lift the leg high enough during walking so that the foot does not drag on the floor. In choreiform gait, the patient will display irregular, jerky, involuntary movements in all extremities. This type of gait is found in certain basal ganglia disorders including Sydenham's chorea, Huntington's disease and other forms of chorea, athetosis or dystonia. In an ataxic gait, caused by cerebellar disease, this gait is described as clumsy, staggering movements with a wide-based gait. The gait of acute alcohol intoxication will resemble the gait of cerebellar disease.

Question 4

You are working as a hospitalist physician assistant, rounding on patients in the intensive care unit. Your shift has nearly ended when you enter the room of your final patient, a 21-year-old Caucasian male in moderate distress with a history of Duchenne muscular dystrophy. While you monitor his health from a global perspective, you recall that the most common cause of death in individuals with this condition is:

A) Congestive Heart Failure
B) Renal failure
C) Respiratory Insufficiency
D) Myocardial Infarction

Accepted Answer

Duchenne muscular dystrophy is characterized by progressive loss of muscle strength, eventually resulting in loss of ambulation, loss of respiratory muscle strength, and death from respiratory insufficiency. The majority of patients also develop cardiomyopathy. While death often results from cardiomyopathy and respiratory complications, the majority of patients die from respiratory insufficiency.

Question 5

What is the suggested laboratory analysis of suspected muscular dystrophy and when do levels peak in adolescence?&#10;A) Creatine phosphokinase, peaks at age 6&#10;B) Myoglobin, peaks at age 2&#10;C) Creatine phosphokinase, peaks at age 2&#10;D) Myoglobin, peaks at age 6

Accepted Answer

Before clinical physical symptoms of Duchenne muscular dystrophy are apparent, the creatine phosphokinase concentrations are already elevated in newborn children. At age two, the levels have been shown to be at their highest, usually 10 to 20 times the upper limit of normal, at times even higher. These levels then progressively fall at a rate of about 25 percent per year, reaching normal CPK levels eventually as muscle is replaced by fat and fibrosis.

Question 6

A concerned parent presents with her four-year-old son whom you recently diagnosed with Duchenne muscular dystrophy. She states that she has always planned on having a large family; however now she worries that the disease will also affect all of her future children and grandchildren. What type of inheritance pattern does this condition follow, in addition to often having de novo mutations?

A) Autosomal dominant
B) Autosomal recessive
C) X-linked dominant
D) X-linked recessive

Accepted Answer

With an X-linked recessive condition, the chance of passing on the changed (non-working) copy of the gene to a child is different for males and females. Males only have one copy of the X chromosome from their mother and one copy of the Y chromosome from their father. Therefore, if their X chromosome has a mutation of their dystrophin gene, they will have Duchenne muscular dystrophy. Females, however, have two copies of X chromosomes. Since females have two copies of this gene, if one copy does not work, they have a second "back-up" copy to produce the dystrophin protein. A woman who has a genetic change in one of her two copies is said to be "a carrier" of Duchenne muscular dystrophy. Carriers do not have Duchenne muscular dystrophy and most are unaware that they even carry this change in their genetic material unless they have a family history. In addition to following an x-linked recessive pattern, "de novo" mutations are also possible, meaning the disorder could arise in any individual, with no previous family history of muscular dystrophy.

Question 7

A grandmother who has recently gained legal custody of her eleven-year-old grandson with Duchenne muscular dystrophy presents to your pediatric office. She admits that because she does not have a computer at home, she is unable to research the condition and is not familiar with the disease process. Today she requests information on the basic management of this condition and questions how many years she has left with her grandson. You explain to her that while there are exceptions, the median age of survival is generally around:

A) 30 years of age
B) 10 years of age
C) 18 years of age
D) 6 years of age

Accepted Answer

Patients with Duchenne muscular dystrophy are often confined to wheelchair by about age 12 years and die in their late teens or twenties from respiratory insufficiency or cardiomyopathy; only a few DMD patients survive beyond the third decade.

Question 8

A 25-year-old Caucasian male presents to a cardiology office for a follow-up on his echocardiogram results. His history includes increased shortness of breath with activity over the last couple of years with no attributable cause, prompting the echocardiogram after an abnormal EKG. The echocardiogram revealed dilated cardiomyopathy with an ejection fraction of 37%. When questioned by the physician assistant about any other symptoms, he admits that he tends to bruise easily as he considers himself "clumsy", often tripping over his own feet. He denies chest pain, numbness of his extremities or paresthesias, trouble with his vision or hearing. What associated condition is this patient most likely suffering from?

A) Becker muscular dystrophy
B) Guillain Barre Syndrome
C) Duchenne muscular dystrophy
D) Multiple Sclerosis

Accepted Answer

Although muscle involvement is less severe than in DMD, cardiac involvement in BMD is often more evident. In one report, for example, echocardiography revealed evidence of cardiac involvement in 60 to 70 percent of patients (mean age 18) with subclinical or benign BMD. It was suggested that, because patients with mild BMD are still able to perform strenuous exercise, the associated mechanical stress on the heart may be harmful for myocardial cells with abnormal dystrophin. Unlike Duchenne muscular dystrophy, individuals with Becker muscular dystrophy often live until mid to late adulthood. If cardiac aspects of this disease are well managed, they can often live a normal lifespan.

Question 9

What is the gold standard for diagnosing Duchenne muscular dystrophy?&#10;A) Muscle Biopsy&#10;B) Creatine Kinase&#10;C) Immunostaining&#10;D) Genetic Testing

Accepted Answer

Molecular genetic testing is indicated for patients with an elevated serum CK level and clinical findings suggestive of a dystrophinopathy. The diagnosis is established if a disease-causing mutation of the dystrophin gene (DMD) is identified.

Question 10

You are examining a six-year-old male patient recently diagnosed with Duchenne muscular dystrophy. As he is sitting on the exam table, you note an excessive lumbar curvature inward when viewed from the side. In the musculoskeletal portion of your physical exam, how do you document this finding?

A) Hyperlordosis
B) Scoliosis
C) Kyphosis
D) Normal anatomical variant

Accepted Answer

As the back muscles of young men with DMD become weaker, lordosis causes their bodies to lean forward, causing a curvature of the spine. DMD can also cause scoliosis, a lateral curvature of the spine, as well as kyphosis, an excessive outward curvature of the spine, however the clinical vignette describes a lordotic presentation.

Deck 15: Muscular Dystrophies