GSD type V (McArdle disease) — MCQs

A 6-month-old girl is brought to the emergency department by her father after he observed jerking movements of her arms and legs earlier in the day. She appears lethargic. Physical examination shows generalized hypotonia. The liver edge is palpable 3 cm below the right costophrenic angle. Her fingerstick glucose shows hypoglycemia. Serum levels of acetone, acetoacetate, and β-hydroxybutyrate are undetectable. Molecular genetic testing shows a mutation in the carnitine palmitoyltransferase II gene. This patient will most likely benefit from supplementation with which of the following?

A 12-year-old male presents to the pediatrician after two days of tea-colored urine which appeared to coincide with the first day of junior high football. He explains that he refused to go back to practice because he was humiliated by the other players due to his quick and excessive fatigue after a set of drills accompanied by pain in his muscles. A blood test revealed elevated creatine kinase and myoglobulin levels. A muscle biopsy was performed revealing large glycogen deposits and an enzyme histochemistry showed a lack of myophosphorylase activity. Which of the following reactions is not occurring in this individual?

A 48-year-old woman comes to the physician because of a 6-month history of muscle stiffness, myalgia, and a 7-kg (15-lb) weight gain. Her last menstrual period was 4 months ago. Physical examination shows cold, dry skin, and proximal muscle weakness. Deep tendon reflexes are 2+ bilaterally, with delayed relaxation. The creatine kinase level is 2,940 U/L. Which of the following is the most appropriate next step in diagnosis?

A 25-year-old man comes to the physician for severe back pain. He describes the pain as shooting and stabbing. On a 10-point scale, he rates the pain as a 9 to 10. The pain started after he lifted a heavy box at work; he works at a supermarket and recently switched from being a cashier to a storekeeper. The patient appears to be in severe distress. Vital signs are within normal limits. On physical examination, the spine is nontender without paravertebral muscle spasms. Range of motion is normal. A straight-leg raise test is negative. After the physical examination has been completed, the patient asks for a letter to his employer attesting to his inability to work as a storekeeper. Which of the following is the most appropriate response?

A 5-year-old boy presents to the pediatrician after his parents noted that he could not sustain physical exertion and would experience muscle cramping. It was noted that after physical exertion the boy experienced severe muscle pain. After a series of biochemical and genetic tests, it was discovered that the boy had a nonsense mutation in the gene encoding the muscle glycogen phosphorylase. Thus he was diagnosed with McArdle's disease. Which of the following mRNA changes would be expected to cause this mutation?

A 13-year-old boy is brought to the physician by his parents, who are concerned about recurrent muscle cramps he experiences while playing soccer. The boy has always loved sports and has been playing in a soccer league for the past 3 years. He now complains of severe cramping pain in his legs after intense practice sessions. He has no significant medical history. His physical examination is unremarkable. A battery of laboratory tests is ordered and they are all normal. Imaging studies yield no abnormalities as well. Which of the following is most likely deficient in this patient?

A 7-year-old boy is brought to his pediatrician by his mother who is worried about his clumsiness. She states that over the past 3 months she has noticed progressive weakness. He used to climb trees and run outside with his cousins, but now he says he gets “too tired.” She’s recently noticed him starting to “walk funny,” despite having “muscular legs.” Upon physical examination, the patient has calf muscle hypertrophy. He uses his arms to rise out of the chair. Labs are obtained that show an elevated creatine kinase. Genetic analysis detects a dystropin gene mutation. A muscle biopsy is performed that reveals reduced dystrophin. Which of the following is the most likely diagnosis?

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

A 15-year-old boy comes to the physician because of severe muscle cramps and pain for 3 months. He first noticed these symptoms while attending tryouts for the high school football team. Since then, he becomes easily fatigued and has severe muscle pain and swelling after 10 minutes of playing. However, after a brief period of rest, the symptoms improve, and he is able to return to the game. Two days ago, he had an episode of reddish-brown urine after playing football. There is no family history of serious illness. He appears healthy. Vital signs are within normal limits. Physical and neurological examinations show no abnormalities. Serum creatine kinase concentration is 333 U/L. Urinalysis shows: Blood 2+ Protein negative Glucose negative RBC negative WBC 1–2/hpf Which of the following is the most likely cause of this patient's symptoms?

A 16-year-old boy comes to the physician because of muscle weakness and cramps for 5 months. He becomes easily fatigued and has severe muscle pain and swelling after 15 minutes of playing basketball with his friends. The symptoms improve after a brief period of rest. After playing, he sometimes also has episodes of reddish-brown urine. There is no family history of serious illness. Serum creatine kinase concentration is 950 U/L. Urinalysis shows: Blood 2+ Protein negative Glucose negative RBC negative WBC 1–2/hpf Which of the following is the most likely underlying cause of this patient's symptoms?