Muscular Dystrophy

Question 1

What is the genetic inheritance of muscular dystrophy?

Answer 1

X-linked disease

Question 2

What is the difference between Duchenne Muscular Dystrophy and Becker Muscular Dystrophy?

Answer 2

Dystrophin is absent in Duchenne and truncated in Becker. Becker MD is less severe, later onset

Question 3

Describe the progression of DMD

Answer 3

Relentless muscle fiber necrosis, Continuous effort at repair and regeneration, progressive necrosis

Question 4

Below is a biopsy of a muscle of a person who has Duchenne Muscular Dystrophy. What are the dark fibers? What are the speckled fibers? What would you find elevated in the serum of a boy with this disease?

Answer 4

Overly contracted fibers; Necrotic muscle fibers invaded by macrophages; Creatine kinase

Question 5

What occurs in pseudohypertrophy in DMD?

Answer 5

Enlargement of a muscle when muscles fibers are replaced by fibroadipose tissue

Question 6

What do patients with Muscular Dystrophy typically die from?

Answer 6

Respiratory insufficiency and/or cardiac arrhythmia

Question 7

What Limb-Girdle Mudcular Dystrophy shows inflammation? Rimmed Vacuoles? What LGMDs are known as sarcoglycanopathies?

Answer 7

LGMD2B, Miyoshi myopathy; LGMD1A; LGMD2C-F

Question 8

Two syndromes exhibit anticipation. What is anticipation and what are these two syndromes?

Answer 8

Anticipation is the process by which symptoms have an earlier age of onset and increased severity of symptoms with the increased number of nucleotide repeats; Myotonic Dystrophy and Oculopharyngeal muscular dystrophy

Question 9

What is the most common form of adult muscular dystrophy?

Answer 9

Myotonic Dystrophy

Question 10

What are the two forms of myotonic dystrophy? How are they inherited?

Answer 10

DM1 and DM2; Autosomal Dominant - DM1 CTG repeat near 3’ end of DMPK gene, DM2 CCTG repteat in first intron of ZNF9 gene

Question 11

What pathology is typically found in myotonic dystrophy?

Answer 11

Most patients display typeI fiber atrophy and hypertrophy of type II fibers;

Question 12

Clinical course of myotonic dystrophy DM1 vs. DM2? What type of myotonic dystrophy is congenital myotonic dystrophy?

Answer 12

DM1 slow progressive muscle weakness at distal limbs vs. proximal weakness in DM2; DM1 congenital DM2 has not been identified

Question 13

A 50 year old patient presents with ptosis, dysphagia and weakness in facial and limb muscles. He is also French-Canadian. What muscular dystrophy does he likely have? What other populations is this condition seen? Genetic findings?

Answer 13

Oculopharyngeal MD; Bukhara Jews, Abnormally increased numbers of GCG repeats in polyA binding protein nuclear 1 gene (PABPN1)

Question 14

A patient has a deletion of part of a repetitive DNA fragment in the subtelomeric region of chromosome 4q. What is the Dx?

Answer 14

Facioscapulohumeral Muscular Dystrophy