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WorksheetsNeuromuscular Disorders and Dystrophinopathies
Total questions: 30
Worksheet time: 45mins
Neuromuscular disorders are characterized primarily by:
Increased bone fragility
Progressive muscle degeneration and weakness
Hyperactive reflexes
Autoimmune destruction of nerves
Duchenne and Becker muscular dystrophy are caused by mutations in which gene?
DMPK
FKRP
DMD
TTN
Duchenne muscular dystrophy (DMD) typically results from mutations that:
Maintain the reading frame
Cause frameshift and absence of dystrophin
Create an extra promoter
Affect only mitochondrial DNA
Becker muscular dystrophy (BMD) typically results from mutations that:
Disrupt the open reading frame
Produce no dystrophin
Preserve the reading frame, producing partially functional dystrophin
Only affect exon 1
Which clinical sign involves a child using their hands to push on their thighs when standing up?
Babinski sign
Trendelenburg sign
Gowers sign
Romberg sign
Which of the following statements about dystrophin is TRUE?
It is a small protein with few exons
It links the extracellular matrix to the sarcomere
It is produced only in cardiac muscle
It is not associated with membrane stability
Which of the following is a typical cause of death in untreated DMD?
Liver failure
Renal insufficiency
Respiratory or cardiac failure
Stroke
Elevated serum creatine kinase (CK) in DMD is typically:
Normal early, high in later stages
High early, lower in later stages as muscle mass disappears
Always low
Highly variable and not diagnostically useful
A 4-year-old boy has difficulty rising from the floor and uses his hands to “climb up” his thighs. His calves appear enlarged. CK level is 12,000 U/L. Genetic testing reveals a deletion of exons 45–52 causing a frameshift. What is the most likely diagnosis?
Becker muscular dystrophy
Duchenne muscular dystrophy
Limb-girdle muscular dystrophy
Spinal muscular atrophy
A 16-year-old boy with slowly progressive proximal weakness can still walk independently. CK is mildly elevated. Genetic testing reveals an in-frame deletion of exons 45–47. What is the expected dystrophin finding?
No dystrophin present
Partial but reduced-size dystrophin
Increased dystrophin expression
Normal dystrophin with abnormal glycosylation
A 5-year-old boy cannot keep up with peers. Examination shows waddling gait and difficulty climbing stairs. CK is 18,000 U/L. Muscle biopsy shows absence of dystrophin. Which mutation pattern is most likely?
In-frame duplication
Out-of-frame deletion
Point mutation in promoter of Dp260
Missense mutation causing partial function
A 3-year-old boy begins to walk on his toes, has frequent falls, and shows a Gowers sign. His mother asks why his calves look so big. What is the correct explanation?
Fat and connective tissue replace muscle
Muscle fibers are growing excessively
Edema from inflammation
Enlarged nerves
A 19-year-old presents with stiffness after contraction, particularly in his hands and jaw. This MOST likely represents:
Myotonic syndrome
Motor neuron disease
Distal neuropathy
Ion channelopathy
Which statement BEST describes the reading frame rule?
In-frame mutations → DMD
Frameshift mutations → BMD
In-frame mutations → BMD; frameshift → DMD
Frameshift mutations have no effect
A 20-year-old woman presents with difficulty smiling and cannot fully close her eyes when sleeping. She also has scapular winging and mild foot drop. CK is mildly elevated. What is the most likely diagnosis?
Duchenne muscular dystrophy
Facioscapulohumeral muscular dystrophy
Limb-girdle muscular dystrophy
Charcot–Marie–Tooth disease
Genetic testing in suspected FSHD typically reveals:
Expansion of CTG repeats on chromosome 19
Deletion of exons in the DMD gene
Contraction of D4Z4 repeats on chromosome 4q35
PMP22 deletion
A 25-year-old man has difficulty releasing his grip after a handshake. He also presents with cataracts. Which condition is most likely?
Limb-girdle muscular dystrophy
Myotonic dystrophy type 1
CMT disease
FSHD
What genetic mechanism causes DM1?
Autosomal recessive nonsense mutations
Trinucleotide CTG repeat expansion in DMPK
PMP22 gene duplication
Deletion of dystrophin exons
A 15-year-old boy presents with high-arched feet, distal leg weakness, foot drop, and absent ankle reflexes. Which diagnosis is most likely?
Duchenne muscular dystrophy
CMT peripheral neuropathy
Myotonic dystrophy
Polymyositis
The most common mutation causing CMT1A is:
CTG expansion in DMPK
PMP22 gene duplication
DMD gene deletion
GDAP1 mutation
A 20-year-old patient with CMT complains of difficulty walking on uneven surfaces. Physical exam shows sensory loss in feet. The MOST likely mechanism is:
Dystrophin deficiency
Axonal degeneration or demyelination of peripheral nerves
Autoimmune nerve attack
Mitochondrial oxidative damage
A man presents with distal weakness, frontal balding, myotonia, testicular atrophy, and cardiac conduction abnormalities. Which mutation category matches this phenotype?
Dystrophin frameshift
CTG repeat expansion
PMP22 duplication
D4Z4 contraction
A 37-year-old parent is asymptomatic but carries a CTG expansion in the DMPK gene. What phenomenon explains why their child has more severe disease?
X-inactivation
Genetic drift
Anticipation
Variable expressivity
G6PD deficiency most commonly manifests clinically as:
Muscle weakness
Acute or chronic hemolytic anemia
Renal failure
Neutropenia
Which food can precipitate hemolysis in G6PD-deficient individuals?
Wheat
Fish
Fava beans
Rice
CYP2D6 poor metabolizers should not receive which drug because it will not be activated?
Codeine
Ibuprofen
Paracetamol
Lorazepam
A 3-year-old boy treated with dapsone + chlorproguanil for malaria develops hemighost cells, spherocytes, and acute hemolytic anemia. Which underlying condition best explains this reaction?
CYP2D6 ultrarapid metabolism
G6PD deficiency
UGT1A1*28 homozygosity
ABCB1 overexpression
A 62-year-old man on codeine, clarithromycin, and voriconazole becomes comatose with respiratory depression. Naloxone rapidly reverses symptoms. What pharmacogenetic explanation fits this case?
Poor CYP2D6 metabolism → codeine inefficacy
CYP2D6 ultrarapid metabolism → morphine toxicity
CYP1A2 overactivity → fast codeine clearance
ABCB1 resistance → poor CNS penetration
A man with neuropathy has PMP22 duplication. Why is this mutation so often de novo with paternal origin?
Maternal imprinting
Increased replication errors in male germline
X-linked inheritance
Mitochondrial transmission
A cancer cell line lacking gene BRCA1 is treated with a PARP inhibitor. Why does it die?
Excess oxidative stress
Synthetic lethality between DNA repair pathways (Synthetic lethality: double loss of repair pathways kills the cell)
P-gp inhibition
Drug activation failure
