A 35-year-old woman presents for evaluation of symmetric proximal muscle weakness. The patient also presents with a blue-purple discoloration of the upper eyelids accompanied by rashes on the knuckles, as shown in the picture below. What is the most likely cause?
ADermatomyositis
BInclusion body myositis
CDuchenne muscular dystrophy
DPolymyositis
EHypothyroidism
A 32-year-old woman presents to the clinic with the complaint of excessive fatigue for the past few weeks. After returning home from the office, she feels too tired to climb up the stairs, comb her hair, or chew her food. She has occasionally experienced double vision. She denies any history of fever, cough, weight loss, night sweats, or snoring. Past history is unremarkable. Physical examination reveals: blood pressure 124/86 mm Hg, heart rate 85/min, respiratory rate 14/min, temperature 37.0°C (98.6°F), and body mass index (BMI) 22.6 kg/m2. On examination, the right upper eyelid is slightly drooping when compared to the left side. Her eye movements are normal. Flexion of the neck is mildly weak. Muscle strength is 5/5 in all 4 limbs. When she is asked to alternately flex and extend her shoulder continuously for 5 minutes, the power in the proximal upper limb muscles becomes 4/5. The muscle tone and deep tendon reflexes are normal. What is the most appropriate test to diagnose this condition?
ACT scan chest
BPlasmapheresis
CTensilon test
DSingle-fiber electromyography
EPresynaptic calcium channel antibodies
A 10-year-old boy is brought to the physician because of recurring episodes of achy muscle pain in his legs. He has a history of poor school performance despite tutoring and has been held back two grades. He is at the 40th percentile for height and 30th percentile for weight. Examination shows ptosis, a high-arched palate, and muscle weakness in the face and hands; muscle strength of the quadriceps and hamstrings is normal. Sensation is intact. Percussion of the thenar eminence causes the thumb to abduct and then relax slowly. Which of the following is the most likely underlying cause?
ADefect of voltage-gated sodium channels of the sarcolemmal membrane
BCTG trinucleotide expansion in the DMPK gene
CComplete impairment of the dystrophin protein
DApoptosis of lower motor neurons
EHumoral immune attack against the endomysial blood vessels
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