Metabolism — MCQs

An 11-year-old girl presents to her primary care physician because she has been having difficulty hearing her teachers at school. She says that the difficulty hearing started about a year ago, and it has slowly been getting worse. Her past medical history is significant for multiple fractures in both her upper and lower extremities. She also recently had a growth spurt and says that her friends say she is tall and lanky. A mutation in which of the following genes is most likely associated with this patient's condition?

A 38-year-old woman presents to the clinic complaining of fatigue and recurrent stomach pain for the past 3 years. She reports an intermittent, dull ache at the epigastric region that is not correlated with food intake. Antacids seem to help a little, but the patient still feels uncomfortable during the episodes. She reports that she has been getting increasingly tired over the past week. The patient denies fevers, chills, nausea, vomiting, melena, hematochezia, or diarrhea but does endorse intermittent abdominal bloating. Her past medical history is significant for type 1 diabetes that is currently managed with an insulin pump. Physical examination demonstrates pale conjunctiva and mild abdominal tenderness at the epigastric region. Laboratory studies are shown below: Leukocyte count: 7,800/mm^3 Segmented neutrophils: 58% Bands: 4% Eosinophils: 2% Basophils: 0% Lymphocytes: 29% Monocytes: 7% Hemoglobin: 10 g/dL Platelet count: 170,000/mm^3 Mean corpuscular hemoglobin concentration: 36 g/dL Mean corpuscular volume: 103 µm^3 Homocysteine: 15 mmol/L (Normal = 4.0 – 10.0 mmol/L) Methylmalonic acid: 0.6 umol/L (Normal = 0.00 – 0.40 umol/L) What substance would you expect to be decreased in this patient?

A 47-year-old homeless man is brought to the emergency department by police, who found him sleeping by the side of the street. He is somnolent and confused and is unable to give a reliable history. His medical history is unobtainable. Vital signs include: temperature 36.9°C (98.4°F), blood pressure 112/75 mm Hg, and pulse 85/min. Physical examination reveals that he has severe truncal ataxia and horizontal gaze palsy with impaired vestibulo-ocular reflexes. Muscle stretch reflexes and motor strength are normal. He has no sensory deficits. Which of the following best represents the most likely etiology of this patient’s condition?

A 32-year-old woman comes to the physician for genetic consultation. She has a history of recurrent generalized seizures, diffuse muscular weakness, and multiple episodes of transient left-sided paresis. She has been hospitalized several times for severe lactic acidosis requiring intravenous fluid hydration. Her 10-year-old daughter also has seizures and muscle weakness. Her 7-year-old son has occasional muscle weakness and headaches but has never had a seizure. Pathologic examination of a biopsy specimen from the woman's soleus muscle shows ragged-appearing muscle fibers. Genetic analysis of the patient's son is most likely to show which of the following?

A homeless woman presents with shortness of breath on exertion and pedal edema. Cardiac workup performed shows evidence of dilated cardiomyopathy and increased cardiac output. She also has decreased sensation over both extremities bilaterally. Which vitamin deficiency most likely caused these symptoms?

A student is experimenting with the effects of nitric oxide in the body. He used a variety of amino acid isolates and measured the resulting nitric oxide levels and the physiological effects on the body. The amino acids function as substrates for nitric oxide synthase. After supplement administration, blood vessels dilated, and the systemic blood pressure decreased. Which of the following amino acids was used in this study?

A 52-year-old man comes to the physician because of a 4-month history of fatigue, weakness, constipation, decreased appetite, and intermittent flank pain. He takes ibuprofen for knee and shoulder pain. Physical examination shows mild tenderness bilaterally in the costovertebral areas. His serum calcium concentration is 11.2 mg/dL, phosphorus concentration is 2.5 mg/dL, and N-terminal parathyroid hormone concentration is 830 pg/mL. Which of the following steps in vitamin D metabolism is most likely increased in this patient?

A 45-year-old man presents with lethargy, muscle aches, and dry skin. He is underweight and has very particular eating habits. Physical examination reveals swollen bleeding gums, cracked lips, petechiae, perifollicular hemorrhage, and corkscrew hairs. Laboratory tests reveal a nutritional deficiency. Which of the following is the key function of the most likely deficient nutrient?

A 1-year-old boy is brought to the physician by his parents for the evaluation of recurrent seizures. He is at the 5th percentile for height and 10th percentile for weight. Examination shows coarse pale hair, inelastic hypopigmented skin, and generalized hypotonia. Laboratory studies show low serum ceruloplasmin levels. Decreased activity of which of the following enzymes is most likely responsible for this patient's condition?

A 55-year-old woman presents to her primary care physician with diarrhea. She states that it has persisted for the past several weeks and has not been improving. She also endorses episodes of feeling particularly flushed in the face. Her temperature is 99°F (37.2°C), blood pressure is 125/63 mmHg, pulse is 100/min, respirations are 15/min, and oxygen saturation is 97% on room air. Physical exam is notable for wheezing on pulmonary exam. The patient is discharged with medications for her symptoms. She returns 2 weeks later with symptoms of diarrhea, dry skin, a non-specific rash, and a notable decline in her memory. Which of the following is the most likely cause of this patient’s most recent presentation?