Muscular dystrophies — MCQs

A 38-year-old man comes to the physician because of a 6-month history of chest discomfort and progressive dyspnea. He cannot do daily chores without feeling out of breath. He was diagnosed in childhood with a milder X-linked dystrophinopathy that has caused progressive proximal muscle weakness and gait abnormalities over the years. Physical examination shows a waddling gait and weak patellar reflexes. Cardiovascular examination shows a holosystolic murmur, displaced point of maximal impulse, and bilateral pitting edema of the ankles. Laboratory studies show elevated levels of brain natriuretic peptide. Which of the following is the most likely underlying cause of this patient's muscle weakness?

A 16-year-old boy is brought to the emergency department after losing consciousness. He had no preceding chest pain or palpitations. His father has cataracts and had frontal balding in his twenties but has no history of cardiac disease. His paternal grandfather also had early-onset balding. His pulse is 43/min. Physical examination shows frontal hair loss, temporal muscle wasting, and testicular atrophy. Neurologic examination shows bilateral foot drop and weakness of the intrinsic hand muscles. An ECG shows bradycardia with third-degree atrioventricular block. The severity of this patient's symptoms compared to that of his father is most likely due to which of the following genetic properties?

A 32-year-old man presents to his primary care provider reporting weakness. He recently noticed that he has difficulty letting go of a doorknob or releasing his hand after shaking hands with others. His past medical history is notable for diabetes, for which he takes metformin. He drinks 2-3 beers per day, uses marijuana occasionally, and works as a security guard. His family history is notable for an early cardiac death in his father. His temperature is 98.6°F (37°C), blood pressure is 130/85 mmHg, pulse is 85/min, and respirations are 18/min. On exam, there is notable muscle atrophy in his hands, feet, and neck. He has delayed hand grip release bilaterally and is slow to return from a smile to a neutral facial expression. His gait is normal, and Romberg's test is negative. He also has frontal balding. This patient’s condition is caused by a mutation in which of the following genes?

A 19-year-old man comes to the physician for the evaluation of progressive difficulty climbing stairs over the last 2 years. During this period, he has also had problems with running, occasional falls, and standing from a chair. He has not had any vision problems or muscle cramping. There is no personal or family history of serious illness. Neurological examination shows deep tendon reflexes are 2+ bilaterally and sensation to pinprick and light touch is normal. Musculoskeletal examination shows enlarged calf muscles bilaterally. He has a waddling gait. Laboratory studies show a creatine kinase level of 1700 U/L. Which of the following is the most appropriate next step to confirm the diagnosis?

A 9-year-old boy is getting fitted for leg braces because he has become too weak to walk without them. He developed normally until age 3 but then he began to get tired more easily and fell a lot. Over time he started having trouble walking and would stand up by using the Gower maneuver. Despite this weakness, his neurologic development is normal for his age. On exam his calves appeared enlarged and he was sent for genetic testing. Sequence data showed that he had a mutation causing a shift in the reading frame, resulting in a severely truncated and non-functional protein. Which of the following types of mutations is most likely the cause of this patient's disorder?

A 3-year-old boy presents to the office with his mother. She states that her son seems weak and unwilling to walk. He only learned how to walk recently after a very notable delay. The boy was born at 39 weeks gestation via spontaneous vaginal delivery. He is up to date on all vaccines and is meeting all verbal and social milestones but he has a great deal of trouble with gross and fine motor skills. Past medical history is noncontributory. He takes a multivitamin every day. The mother states that some boys on her side of the family have had similar symptoms and worries that her son might have the same condition. Today, the boy’s vital signs include: blood pressure 110/65 mm Hg, heart rate 90/min, respiratory rate 22/min, and temperature 37.0°C (98.6°F). On physical exam, the boy appears well developed and pleasant. He sits and listens and follows direction. His heart has a regular rate and rhythm and his lungs are clear to auscultation bilaterally. He struggles to get up to a standing position after sitting on the floor. A genetic study is performed that reveals a significant deletion in the gene that codes for dystrophin. Which of the following is the most likely diagnosis?

A 15-year-old boy comes to the physician for the evaluation of progressive difficulty climbing stairs for the last 2 years. During this period, he has also had problems running and standing up from a seated position. He is at the 50th percentile for height and weight. Examination shows enlarged calf muscles bilaterally and a waddling gait. Which of the following is the most likely cause of this patient's condition?

A 7-year-old boy is brought to the emergency department by his parents. He is complaining of left-sided knee pain which has progressively increased in severity over the past 2 days. It started when he was playing football with his brothers but he does not recall falling or getting any injury. Past medical history is significant for prolonged bleeding and easy bruising. His maternal uncle has similar problems. Physical exam reveals swollen and painful left knee. His laboratory investigations reveal: Hemoglobin 11.8 g/dL WBC count 7,000/mL Platelets 250,000/mL INR 0.9 aPTT 62 sec, fully corrected with a mixing study Which of the following disorders have the same mode of inheritance as this patient’s disease?

A 17-year-old boy is brought to the pediatrician by his mother for fatigue. The patient reports that he was supposed to try out for winter track this year, but he had to quit because his “legs just give up.” He also reports increased difficulty breathing with exercise but denies chest pain or palpitations. He has no chronic medical conditions and takes no medications. He has had no surgeries in the past. The mother reports that he met all his pediatric milestones and is an “average” student. He is up-to-date on all childhood vaccinations, including a recent flu vaccine. On physical examination, there is mild lumbar lordosis. The patient’s thighs appear thin in diameter compared to his lower leg muscles, and he walks on his toes. An electrocardiogram shows 1st degree atrioventricular nodal block. Which of the following is the most likely cause of the patient’s condition?

A 4-year-old male child presents with muscle weakness. His mother tells that her child has difficulty in climbing stairs and getting up from the floor. On muscle biopsy, small muscle fibrils and absence of dystrophin was found. What is the diagnosis out of given options?