[MCQ] Muscular Dystrophies- Part 3

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Muscular Dystrophies- Part 3

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Question 1

Which of the following about Kearns-Sayre Syndrome (KSS) is false ?

A	Onset before 20 years of age
B	CPEO
C	Pigmentary retinopathy
D	Diplopia

Question 1 Explanation:

In CPEO, varying degrees of ptosis & weakness of extraocular muscles are seen, usually in the absence of diplopia, a point of distinction from myasthenia gravis. Triad of clinical findings in KSS includes onset before age 20, CPEO, and pigmentary retinopathy, plus one or more of the f

Question 2

Which of the following is a cardinal sign of mitochondrial disorders ?

A	Diabetes mellitus
B	Addison’s disease
C	Hypoparathyroidism
D	Hyperaldosteronism

Question 2 Explanation:

Diabetes mellitus is a cardinal sign of mitochondrial disorders and occurs in 13% of KSS patients

Question 3

Which of the following about KSS is false ?

A	Sporadic disorder
B	Caused by single mtDNA deletions
C	Spontaneous deletion occur in ovum or zygote
D	Spontaneous deletion occur in spermatozoa

Question 3 Explanation:

KSS is a sporadic disorder. The disease is caused by single mtDNA deletions arising spontaneously in the ovum or zygote. The most common deletion removes 4,977 bp of contiguous mtDNA

Question 4

Which of the following is false about progressive external ophthalmoplegia (PEO) ?

A	Due to mtDNA mutations
B	Inherited in a Mendelian fashion
C	Onset is usually after puberty
D	Ragged red fibers seen in muscle biopsy

Question 4 Explanation:

PEO is caused by nuclear DNA mutations affecting mtDNA copy number & integrity. It is inherited in a Mendelian fashion. Onset is usually after puberty. CSF protein is normal. Ragged red fibers are prominently seen in muscle biopsy.

Question 5

Which of the following chromosome is affected in autosomal dominant form of CPEO ?

A	4q35
B	10q24
C	15q22–26
D	All of the above

Question 5 Explanation:

Autosomal dominant form of CPEO is linked to loci on 3 chromosomes - 4q35, 10q24 & 15q22–26.

Question 6

“Twinkle” is the gene product of ?

A	4q35
B	10q24
C	15q22–26
D	All of the above

Question 6 Explanation:

In chromosome 10q–related CPEO, mutations occur in C10orf2 gene. Its gene product is twinkle, named for its punctate, starlike staining properties. It co-localizes with mtDNA and is critical for lifetime maintenance of mitochondrial integrity.

Question 7

Enzyme important in mtDNA replication is ?

A	Carnitine palmitoyltransferase (CPT) I
B	Acid maltase
C	Myoadenylate deaminase
D	POLG

Question 7 Explanation:

In CPEO mapped to chromosome 15q, a mutation affects the gene encoding mtDNA polymerase (POLG), an enzyme important in mtDNA replication.

Question 8

Characteristic feature of myoclonic epilepsy with ragged red fibers (MERRF) is ?

A	Myoclonic epilepsy
B	Cerebellar ataxia
C	Progressive muscle weakness
D	All of the above

Question 8 Explanation:

Characteristic features include myoclonic epilepsy, cerebellar ataxia, and progressive muscle weakness in a limb-girdle distribution. Other more variable features include dementia, peripheral neuropathy, optic atrophy, hearing loss, and diabetes mellitus.

Question 9

To be called ragged red fiber, which of the following is abnormal in a muscle cell ?

A	Golgi apparatus
B	Mitochondria
C	Cell membrane
D	Nucleus

Question 9 Explanation:

Term ragged red fibers was coined by Olson (1972) to describe muscle fibers with significant numbers of abnormal mitochondria (enlarged, bizarrely shaped with crystalline inclusions) highlighted with modified trichrome stain.

Question 10

Which of the following is caused by maternally inherited point mutations of mitochondrial tRNA gene ?

A	Kearns-Sayre Syndrome (KSS)
B	MERRF
C	Pompe’s Disease
D	All of the above

Question 10 Explanation:

MERRF & MELAS are caused by maternally inherited point mutations of mitochondrial tRNA genes.

Question 11

Which of the following about Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke like Episodes (MELAS) is false ?

A	Cerebral lesions conform to a vascular distribution
B	Partial motor or generalized seizures
C	Serum lactic acid is elevated
D	Muscle biopsies show ragged red fibers

Question 11 Explanation:

In MELAS, the term stroke like is appropriate because cerebral lesions do not conform to a strictly vascular distribution. Like KSS, onset is before age 20. Seizures are partial motor or generalized. Cerebral insults cause hemiparesis, hemianopia, and cortical blindness. Serum lactic acid is typically elevated. CSF protein is increased. Muscle biopsies show ragged red fibers.

Question 12

Which of the following about Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke like Episodes (MELAS) is false ?

A	Focal lesions in frontal lobes
B	Basal ganglia calcification
C	Vascular territories are not respected
D	Cerebral angiography essentially normal

Question 12 Explanation:

IN MELAS, neuroimaging shows basal ganglia calcification. Focal lesions mimiking infarction are seen mainly in occipital & parietal lobes. Strict vascular territories are not respected, and cerebral angiography does not show lesions of the major cerebral blood vessels.

Question 13

Which of the following is caused by maternally inherited point mutations of mitochondrial tRNA gene ?

A	Kearns-Sayre Syndrome (KSS)
B	MELAS
C	Pompe’s Disease
D	Mitochondrial DNA depletion syndrome (MDS)

Question 13 Explanation:

MERRF & MELAS are caused by maternally inherited point mutations of mitochondrial tRNA genes.

Question 14

Which of the following point mutation is most common in MELAS ?

A	A3243G point mutation in tRNALeu(UUR)
B	3252G point mutation in tRNALeu(UUR)
C	3256T point mutation in tRNALeu(UUR)
D	3271C point mutation in tRNALeu(UUR)

Question 14 Explanation:

In MELAS, A3243G point mutation in tRNALeu(UUR) is the most common (80%).

Question 15

Which of the following is a calcium channelopathy ?

A	Hypokalemic periodic paralysis
B	Hyperkalemic periodic paralysis
C	Paramyotonia congenita
D	Andersen-Tawil Syndrome

Question 16

Which of the following is a potassium channelopathy ?

A	Hypokalemic periodic paralysis
B	Hyperkalemic periodic paralysis
C	Paramyotonia congenita
D	Andersen-Tawil Syndrome

Question 17

Hypokalemic periodic paralysis type 1 is caused by mutation in which of the following gene ?

A	CALCL1A1
B	CALCL1A2
C	CALCL1A3
D	CALCL1A4

Question 17 Explanation:

HypoKPP type 1 is inherited as an autosomal dominant disorder with incomplete penetrance. It is due to mutations in voltage-sensitive, skeletal muscle calcium channel gene, CALCL1A3. HypoKPP type 2 is due to mutations in voltage-sensitive sodium channel gene (SCN4A). The muscle cell depolarizes when potassium levels are low.

Question 18

Onset of hypokalemic periodic paralysis (HypoKPP) is at ?

A	Childhood
B	Adolescence
C	Adulthood
D	Middle age

Question 18 Explanation:

Onset of hypokalemic periodic paralysis (Hypokpp) occurs at adolescence. Episodic weakness with onset after age 25 is almost never due to periodic paralyses.

Question 19

In hypokalemic periodic paralysis, preferred vehicle for administration of IV potassium is

A	Normal saline
B	GDW
C	Ringer lactate
D	Mannitol

Question 19 Explanation:

Treatment of hypokalemic periodic paralysis is oral KCl (0.2 - 0.4 mmol/kg), every 30 minutes. Should IV therapy become necessary (swallowing problems or vomiting), Mannitol is the preferred vehicle for administration of IV potassium as glucose solution may further reduce serum potassium levels.

Question 20

Hyperkalemic periodic paralysis (HyperKPP) is caused by mutation in which of the following gene ?

A	SCN1A
B	SCN2A
C	SCN3A
D	SCN4A

Question 20 Explanation:

HyperKPP is an autosomal dominant disorder due to mutations of voltage-gated sodium channel SCN4A gene.

Question 21

Attacks of muscle weakness are induced by cold in which of the following ?

A	Thomsen’s disease
B	Becker’s disease
C	Paramyotonia congenita
D	All of the above

Question 21 Explanation:

In paramyotonia congenita (PC), the attacks of weakness are cold-induced or occur spontaneously. Myotonia in chloride channel disorders - Thomsen’s disease and Becker’s disease is worsened by cold and improved by activity.

Question 22

Long QT syndrome is a feature of which of the following ?

A	Thomsen’s disease
B	Becker’s disease
C	Paramyotonia congenita
D	Andersen-Tawil Syndrome

Question 22 Explanation:

Autosomal dominant Andersen-Tawil Syndrome is a potassium channel disorder characterized by episodic weakness, cardiac arrhythmias (long QT, ventricular ectopy, bidirectional ventricular arrhythmias), and dysmorphic features (short stature, scoliosis, clinodactyly, hypertelorism, small or prominent low-set ears, micrognathia, and broad forehead). It is caused by mutations of the inwardly rectifying potassium channel (Kir 2.1) gene that heighten muscle cell excitability.

Question 23

Serum CK level is most conspicuously elevated in which of the following endocrine myopathies ?

A	Hyperthyroidism
B	Hypothyroidism
C	Hyperparathyroidism
D	Diabetes mellitus

Question 23 Explanation:

In hypothyroidism, serum CK level is elevated (up to 10 times normal), even when there is minimal clinical evidence of muscle disease. EMG is typically normal.

Question 24

Characteristic prolongation of relaxation phase of muscle stretch reflexes in hypothyroidism is best observed in ?

A	Triceps reflex
B	Biceps reflex
C	Supinator reflex
D	Knee reflex

Question 24 Explanation:

Relaxation phase of muscle stretch reflexes is characteristically prolonged in hypothyroidism and is best observed at the ankle or biceps brachii reflexes.

Question 25

Which class of the following lipid-lowering agents causes myopathy ?

A	Fibrates
B	HMG-CoA reductase inhibitors (statins)
C	Niacin (nicotinic acid)
D	All of the above

Question 25 Explanation:

All classes of lipid-lowering agents have been implicated in muscle toxicity, including fibrates (clofibrate, gemfibrozil), HMG-CoA reductase inhibitors (statins), niacin (nicotinic acid) & ezetimibe

Question 26

“Acute quadriplegic” myopathy best relates to ?

A	Glucocorticoid related myopathy
B	Lipid-lowering agent related myopathy
C	Vitamin D related myopathy
D	Vitamin E related myopathy

Question 26 Explanation:

Glucocorticoid myopathy occurs with chronic treatment or as “acute quadriplegic” myopathy secondary to high-dose IV glucocorticoid use. Acute quadriplegic myopathy can also occur in sepsis.

Question 27

Which of the following glucocorticoid pose a high risk for myopathy ?

A	Triamcinolone
B	Betamethasone
C	Dexamethasone
D	All of the above

Question 27 Explanation:

Fluorinated glucocorticoids like triamcinolone, betamethasone and dexamethasone pose a high risk for myopathy.

Question 28

Which of the following medication can caise mitochondrial myopathy with ragged red fibers ?

A	Zidovudine
B	D-penicillamine
C	Glucocorticoids
D	Vitamin D

Question 28 Explanation:

Zidovudine myopathy produces muscle atrophy affecting thigh & calf muscles. Muscle biopsy shows ragged red fibers with minimal inflammation.

Question 29

Drug-related inflammatory or antibody-mediated myopathy is caused by which of the following medications ?

A	Zidovudine
B	D-penicillamine
C	Glucocorticoids
D	Vitamin D

Question 29 Explanation:

Drug-related inflammatory or antibody-mediated myopathy is most consistently caused by Dpenicillamine. Myasthenia gravis and polymyositis can also occur with D-penicillamine.

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See all quizzes of Muscular Dystrophies- Part 3 here:

1 Which of the following about Kearns-Sayre Syndrome (KSS) is
false ?
A. Onset before 20 years of age
B. CPEO
C. Pigmentary retinopathy
D. Diplopia

2 Which of the following is a cardinal sign of mitochondrial
disorders ?
A. Diabetes mellitus
B. Addison’s disease
C. Hypoparathyroidism
D. Hyperaldosteronism

3 Which of the following about KSS is false ?
A. Sporadic disorder
B. Caused by single mtDNA deletions
C. Spontaneous deletion occur in ovum or zygote
D. Spontaneous deletion occur in spermatozoa

4 Which of the following is false about progressive external
ophthalmoplegia (PEO) ?
A. Due to mtDNA mutations
B. Inherited in a Mendelian fashion
C. Onset is usually after puberty
D. Ragged red fibers seen in muscle biopsy

5 Which of the following chromosome is affected in autosomal
dominant form of CPEO ?
A. 4q35
B. 10q24
C. 15q22–26
D. All of the above

6 “Twinkle” is the gene product of ?
A. 4q35
B. 10q24
C. 15q22–26
D. All of the above

7 Enzyme important in mtDNA replication is ?
A. Carnitine palmitoyltransferase (CPT) I
B. Acid maltase
C. Myoadenylate deaminase
D. POLG

8 Characteristic feature of myoclonic epilepsy with ragged red fibers
(MERRF) is ?
A. Myoclonic epilepsy
B. Cerebellar ataxia
C. Progressive muscle weakness
D. All of the above

9 To be called ragged red fiber, which of the following is abnormal
in a muscle cell ?
A. Golgi apparatus
B. Mitochondria
C. Cell membrane
D. Nucleus

10 Which of the following is caused by maternally inherited point
mutations of mitochondrial tRNA gene ?
A. Kearns-Sayre Syndrome (KSS)
B. MERRF
C. Pompe’s Disease
D. All of the above

11 Which of the following about Mitochondrial Myopathy,
Encephalopathy, Lactic Acidosis, and Stroke like Episodes
(MELAS) is false ?
A. Cerebral lesions conform to a vascular distribution
B. Partial motor or generalized seizures
C. Serum lactic acid is elevated
D. Muscle biopsies show ragged red fibers

12 Which of the following about Mitochondrial Myopathy,
Encephalopathy, Lactic Acidosis, and Stroke like Episodes
(MELAS) is false ?
A. Focal lesions in frontal lobes
B. Basal ganglia calcification
C. Vascular territories are not respected
D. Cerebral angiography essentially normal

13 Which of the following is caused by maternally inherited point
mutations of mitochondrial tRNA gene ?
A. Kearns-Sayre Syndrome (KSS)
B. MELAS
C. Pompe’s Disease
D. Mitochondrial DNA depletion syndrome (MDS)

14 Which of the following point mutation is most common in
MELAS ?
A. A3243G point mutation in tRNALeu(UUR)
B. 3252G point mutation in tRNALeu(UUR)
C. 3256T point mutation in tRNALeu(UUR)
D. 3271C point mutation in tRNALeu(UUR)

15 Which of the following is a calcium channelopathy ?
A. Hypokalemic periodic paralysis
B. Hyperkalemic periodic paralysis
C. Paramyotonia congenita
D. Andersen-Tawil Syndrome
16 Which of the following is a potassium channelopathy ?
A. Hypokalemic periodic paralysis
B. Hyperkalemic periodic paralysis
C. Paramyotonia congenita
D. Andersen-Tawil Syndrome
17 Hypokalemic periodic paralysis type 1 is caused by mutation in
which of the following gene ?
A. CALCL1A1
B. CALCL1A2
C. CALCL1A3
D. CALCL1A4

18 Onset of hypokalemic periodic paralysis (HypoKPP) is at ?
A. Childhood
B. Adolescence
C. Adulthood
D. Middle age

19 In hypokalemic periodic paralysis, preferred vehicle for
administration of IV potassium is ?
A. Normal saline
B. GDW
C. Ringer lactate
D. Mannitol

20 Hyperkalemic periodic paralysis (HyperKPP) is caused by mutation
in which of the following gene ?
A. SCN1A
B. SCN2A
C. SCN3A
D. SCN4A

21 Attacks of muscle weakness are induced by cold in which of the
following ?
A. Thomsen’s disease
B. Becker’s disease
C. Paramyotonia congenita
D. All of the above

22 Long QT syndrome is a feature of which of the following ?
A. Thomsen’s disease
B. Becker’s disease
C. Paramyotonia congenita
D. Andersen-Tawil Syndrome

23 Serum CK level is most conspicuously elevated in which of the
following endocrine myopathies ?
A. Hyperthyroidism
B. Hypothyroidism
C. Hyperparathyroidism
D. Diabetes mellitus

24 Characteristic prolongation of relaxation phase of muscle stretch
reflexes in hypothyroidism is best observed in ?
A. Triceps reflex
B. Biceps reflex
C. Supinator reflex
D. Knee reflex

25 Which class of the following lipid-lowering agents causes
myopathy ?
A. Fibrates
B. HMG-CoA reductase inhibitors (statins)
C. Niacin (nicotinic acid)
D. All of the above

26 “Acute quadriplegic” myopathy best relates to ?
A. Glucocorticoid related myopathy
B. Lipid-lowering agent related myopathy
C. Vitamin D related myopathy
D. Vitamin E related myopathy

27 Which of the following glucocorticoid pose a high risk for
myopathy ?
A. Triamcinolone
B. Betamethasone
C. Dexamethasone
D. All of the above

28 Which of the following medication can caise mitochondrial
myopathy with ragged red fibers ?
A. Zidovudine
B. D-penicillamine
C. Glucocorticoids
D. Vitamin D

29 Drug-related inflammatory or antibody-mediated myopathy is
caused by which of the following medications ?
A. Zidovudine
B. D-penicillamine
C. Glucocorticoids
D. Vitamin D

Muscular Dystrophies

[MCQ] Muscular Dystrophies- Part 3

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Muscular Dystrophies- Part 3

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