Inborn errors of metabolism — MCQs

A 27-year-old woman gives birth to a boy at 36 weeks gestational age. The infant weighs 4022 grams at birth, is noted to have a malformed sacrum, and appears to be in respiratory distress. Apgar scores are 5 and 7 at 1 minute and 5 minutes respectively. Hours after birth, the infant is found to be irritable, bradycardic, cyanotic, and hypotonic, and the infant's serum is sent to the laboratory for evaluation. Which of the following abnormalities would you expect to observe in this infant?

A 10-year-old boy is brought to the emergency department due to vomiting and weakness. He is attending a summer camp and was on a hike with the other kids and a camp counselor. His friends say that the boy skipped breakfast, and the counselor says he forgot to pack snacks for the kids during the hike. The child’s parents are contacted and report that the child has been completely healthy since birth. They also say there is an uncle who would have to eat regularly or he would have similar symptoms. At the hospital, his heart rate is 90/min, respiratory rate is 17/min, blood pressure is 110/65 mm Hg, and temperature is 37.0°C (98.6°F). Physical examination reveals a visibly lethargic child with slight disorientation to time and place. Mild hepatosplenomegaly is observed but no signs of dehydration are noted. A blood sample is drawn, and fluids are started via an intravenous line. Lab report Serum glucose 44 mg/dL Serum ketones absent Serum creatinine 1.0 mg/dL Blood urea nitrogen 32 mg/dL Alanine aminotransferase (ALT) 425 U/L Aspartate aminotransferase (AST) 372 U/L Hemoglobin (Hb%) 12.5 g/dL Mean corpuscular volume (MCV) 80 fl Reticulocyte count 1% Erythrocyte count 5.1 million/mm3 Which of the following is most likely deficient in this patient?

A 3-week-old newborn is brought to the pediatrician by his mother. His mother is concerned about her son’s irritability and vomiting, particularly after breastfeeding him. The infant was born at 39 weeks via spontaneous vaginal delivery. His initial physical was benign. Today the newborn appears mildly jaundiced with palpable hepatomegaly, and his eyes appear cloudy, consistent with the development of cataracts. The newborn is also in the lower weight-age percentile. The physician considers a hereditary enzyme deficiency and orders blood work and a urinalysis to confirm his diagnosis. He recommends that milk and foods high in galactose and/or lactose be eliminated from the diet. Which of the following is the most likely deficient enzyme in this metabolic disorder?

A 2-day-old male is seen in the newborn nursery for repeated emesis and lethargy. He was born at 39 weeks to a 24-year-old mother following an uncomplicated pregnancy and birth. He has been breastfeeding every 2 hours and has 10 wet diapers per day. His father has a history of beta-thalassemia minor. Laboratory results are as follows: Hemoglobin: 12 g/dL Platelet count: 200,000/mm³ Mean corpuscular volume: 95 µm³ Reticulocyte count: 0.5% Leukocyte count: 5,000/mm³ with normal differential Serum: Na+: 134 mEq/L Cl-: 100 mEq/L K+: 3.3 mEq/L HCO3-: 24 mEq/L Urea nitrogen: 1 mg/dL Creatinine: 0.6 mg/dL Ammonia: 150 µmol/L (normal: 50-80 µmol/L) Which of the following is the most likely diagnosis?

An 8-month-old female infant from a first-degree consanguineous couple was brought to the physician because the mother noticed abnormalities in the growth of her child as well as the different lengths of her child's legs. The infant had gingival hyperplasia, restricted movement in both shoulders, a prominent, pointed forehead, and enophthalmos with a slight opacity in both corneas. A blood test revealed 10 fold higher than normal levels of the following enzymes: N-acetyl-ß-glucosaminidase, ß-glucuronidase, ß-hexosaminidase A, and alkaline phosphatase. Which of the following is most likely deficient in this patient?

You are counseling a mother whose newborn has just screened positive for a deficit of phenylalanine hydroxylase enzyme. You inform her that her child will require dietary supplementation of which of the following?

A 2-week-old boy presents to the emergency department because of unusual irritability and lethargy. The patient is admitted to the pediatric intensive care unit and minutes later develops metabolic encephalopathy. This progressed to a coma, followed by death before any laboratory tests are completed. The infant was born at home via vaginal delivery at 39 weeks' of gestation. His mother says that the symptoms started since the infant was 4-days-old, but since he only seemed ‘tired’, she decided not to seek medical attention. Further testing during autopsy shows hyperammonemia, low citrulline, and increased orotic acid. Which of the following enzymes is most likely deficient in this patient?

On a medical trip to Nicaragua, you observe a sweet odor in the cerumen of a 12-hour-old female newborn. Within 48 hours, the newborn develops ketonuria, poor feeding, and a sweet odor is also noticed in the urine. By 96 hours, the newborn is extremely lethargic and opisthotonus is observed. In order to prevent a coma and subsequent death, which of the following amino acids is one of those that should be withheld from this newborn's diet?

A 9-month-old girl is brought to the physician because of a 1-month history of poor feeding and irritability. She is at the 15th percentile for height and 5th percentile for weight. Examination shows hypotonia and wasting of skeletal muscles. Cardiopulmonary examination shows no abnormalities. There is hepatomegaly. Her serum glucose is 61 mg/dL, creatinine kinase is 100 U/L, and lactic acid is within the reference range. Urine ketone bodies are elevated. Which of the following enzymes is most likely deficient in this patient?

A 3-year-old male presents with his parents to a pediatrician for a new patient visit. The child was recently adopted and little is known about his prior medical or family history. The parents report that the child seems to be doing well, but they are concerned because the patient is much larger than any of the other 3-year-olds in his preschool class. They report that he eats a varied diet at home, and that they limit juice and snack foods. On physical exam, the patient is in the 73rd percentile for weight, 99th percentile for height, and 86th percentile for head circumference. He appears mildly developmentally delayed. He has a fair complexion and tall stature with a prominent sternum. The patient also has joint hypermobility and hyperelastic skin. He appears to have poor visual acuity and is referred to an ophthalmologist, who diagnoses upward lens subluxation of the right eye. This child is most likely to develop which of the following complications?