KMU Past Paper Practice
Topic 12 — Skeletal-Muscle Atrophy, Myopathies and Muscular Dystrophies
3rd Year MBBS • 20 A-type Single Best Answer MCQs
MCQ 1
A 72-year-old man has gradually reduced muscle mass and strength without focal nerve injury or inflammatory symptoms. Muscle biopsy shows small fibres without prominent necrosis. Which factor most likely contributes to this age-related change?
Options:
Loss of motor units with reduced anabolic support
Aging causes sarcopenia through gradual motor-unit loss, reduced activity and decreased anabolic support, producing progressive reduction in muscle mass and strength.
MCQ 2
A patient remains confined to bed for several months after a major operation. The thigh muscles become visibly smaller, but there is no sensory loss or evidence of nerve injury. Which cellular change best explains the reduced muscle bulk?
Options:
Loss of myofilaments from individual fibres
Disuse reduces protein synthesis and increases protein breakdown, causing loss of contractile elements and shrinkage of individual muscle fibres.
MCQ 3
A muscle biopsy shows rounded fibres of variable size, scattered necrotic fibres, regenerating basophilic fibres and centrally placed nuclei. Which interpretation is most appropriate?
Options:
A primary disorder of skeletal muscle
Scattered necrosis, regeneration, fibre-size variation and internal nuclei form a typical myopathic pattern rather than a grouped neurogenic pattern.
MCQ 4
A 36-year-old woman has proximal weakness, dysphagia and erythematous papules over the knuckles. Biopsy shows inflammation around vessels and within perimysial connective tissue. Which process is primarily responsible for muscle damage?
Options:
Microvascular immune injury causing ischemia
Dermatomyositis primarily involves immune-mediated damage to small vessels, producing reduced perfusion and perifascicular muscle injury.
MCQ 5
A 50-year-old patient has progressive symmetrical weakness of shoulder and pelvic-girdle muscles. There is no rash. Muscle biopsy shows endomysial inflammation and scattered fibre necrosis. Which cell population is expected to predominate?
Options:
Cytotoxic T lymphocytes around fibres
Polymyositis is characterized by endomysial cytotoxic T cells that surround and directly injure muscle fibres.
MCQ 6
A 67-year-old man has gradually progressive difficulty gripping tools and rising from a chair. Weakness is unequal on the two sides. Which distribution would further support inclusion-body myositis?
Options:
Quadriceps muscles and finger flexors
Inclusion-body myositis characteristically affects quadriceps and finger flexors and may produce asymmetric proximal and distal weakness.
MCQ 7
A patient develops proximal weakness after prolonged treatment with a medicine known to increase protein catabolism. Muscle biopsy shows selective fibre atrophy without significant necrosis or inflammation. Which clinical finding is most consistent with this condition?
Options:
Painless weakness with modest enzyme elevation
Glucocorticoid-associated myopathy causes painless proximal weakness through muscle protein breakdown, with little inflammation and no major creatine-kinase rise.
MCQ 8
A 35-year-old man develops muscle pain and weakness shortly after starting a new medication. The physician suspects a toxic myopathy. Which history finding would provide the strongest support for this diagnosis?
Options:
Symptoms beginning after drug exposure
A clear temporal relationship between exposure and muscle symptoms is a major diagnostic clue in toxic myopathy.
MCQ 9
A 5-year-old boy has progressive proximal weakness. His maternal uncle had a similar illness. Muscle biopsy shows necrosis, regeneration and fatty replacement. Which genetic pattern best explains the family history?
Options:
X-linked recessive transmission
Duchenne muscular dystrophy is X-linked recessive, so affected boys may be connected through carrier females in the maternal family.
MCQ 10
A boy with a dystrophinopathy develops increasing endomysial fibrosis and reduced muscle power despite the presence of regenerating fibres. Why does weakness continue to progress?
Options:
Repeated injury exceeds regenerative capacity
Continuous contraction-related fibre damage eventually overwhelms regeneration, causing irreversible fibre loss, fibrosis and fatty replacement.
MCQ 11
A 7-year-old boy with an established muscular dystrophy is being assessed for systemic complications. Which additional evaluation is most important because the defective protein is also expressed outside skeletal muscle?
Options:
Cardiac and respiratory assessment
Dystrophin deficiency can affect cardiac and respiratory muscles, leading to cardiomyopathy and progressive ventilatory weakness.
MCQ 12
A newborn has severe hypotonia, feeding difficulty and poor respiratory effort. Muscle biopsy identifies rod-like structures inside muscle fibres. Which diagnosis is most likely?
Options:
Nemaline myopathy
Nemaline myopathy is a congenital structural myopathy characterized by rod-like nemaline bodies within affected muscle fibres.
MCQ 13
An infant with congenital hypotonia undergoes evaluation. The clinician wants to establish whether the disorder is inherited and identify its exact cause. Which investigation provides the most definitive etiological information?
Options:
Targeted genetic analysis
Genetic analysis can directly identify the pathogenic variant and establish the inherited cause of a congenital or hereditary myopathy.
MCQ 14
A 28-year-old woman has weakness, muscle pain and elevated creatine kinase. Examination reveals a characteristic skin eruption. Which investigation would most directly demonstrate the tissue pattern responsible for her disease?
Options:
Muscle biopsy
Muscle biopsy can directly show perivascular inflammation and perifascicular atrophy, confirming the characteristic pathological pattern.
MCQ 15
A man has permanent lower-limb paralysis following poliomyelitis. He is unable to walk independently but remains socially active using a wheelchair. Which term best describes his difficulty in walking?
Options:
Disability
Difficulty performing the activity of walking is a disability; paralysis is the impairment, while social disadvantage would represent handicap.
MCQ 16
Two public-health programmes are being compared. Programme X prevents years of premature death, while programme Y reduces years lived with severe physical limitation. Which feature makes DALY suitable for this comparison?
Options:
It combines mortality and disability loss
DALY combines years of life lost from premature death with years lived in less than full health.
MCQ 17
A health economist compares two rehabilitation interventions. One provides more additional years of life with good mobility and independence. Which outcome measure is most appropriate?
Options:
Quality-adjusted life years
QALYs combine the duration of survival with the quality of health experienced during those years.
MCQ 18
A district continues to report poliovirus transmission despite repeated vaccination campaigns. Review shows that many children in mobile communities are repeatedly missed. Which determinant most directly sustains transmission?
Options:
Incomplete population immunity
Repeatedly missed children create immunity gaps that allow poliovirus to circulate among susceptible individuals.
MCQ 19
Poliovirus is detected in sewage from a densely populated locality. No child with paralysis has yet been identified. Which public-health action is most appropriate?
Options:
Strengthen vaccination and surveillance promptly
Environmental detection indicates possible silent circulation and requires rapid action to close immunity gaps and identify transmission.
MCQ 20
A child recovering from paralytic poliomyelitis has weak lower limbs and early ankle stiffness. Which rehabilitation plan best prevents further functional loss while promoting independence?
Options:
Gentle exercise, stretching and suitable orthoses
Appropriate physiotherapy and orthotic support preserve joint movement, reduce contracture and improve safe functional mobility.