Sulfur-containing amino acid metabolismDownloads

A 21-year-old man presents to the emergency department with acute back pain. The pain began a few hours prior to presentation and is located on the left lower back. The pain is described to be “shock-like,” 9/10 in pain severity, and radiates to the left groin. His temperature is 98.6°F (37°C), blood pressure is 120/75 mmHg, pulse is 101/min, and respirations are 18/min. The patient appears uncomfortable and is mildly diaphoretic. There is costovertebral angle tenderness and genitourinary exam is unremarkable. A non-contrast computerized tomography (CT) scan of the abdomen and pelvis demonstrates an opaque lesion affecting the left ureter with mild hydronephrosis. Straining of the urine with urine crystal analysis is demonstrated. Which of the following amino acids is most likely poorly reabsorbed by this patient’s kidney?

A 35-year-old woman comes to the physician because of a 1-day history of swelling and pain in the left leg. Two days ago, she returned from a business trip on a long-distance flight. She has alcohol use disorder. Physical examination shows a tender, swollen, and warm left calf. Serum studies show an increased homocysteine concentration and a methylmalonic acid concentration within the reference range. Further evaluation of this patient is most likely to show which of the following serum findings?