A pediatric resident is caring for a term infant who is lethargic and vomiting at 24 hours of life. Plasma ammonia is markedly elevated, and pH is normal. What is the most likely diagnosis?
A 6-year-old boy develops exercise-induced muscle pain, early fatigue, and dark urine after exertion, with a ‘second-wind’ phenomenon allowing him to continue activity after a brief rest. He is treated with pre-exercise carbohydrate loading, including cornstarch supplementation, to improve exercise tolerance. Which disease is this therapy used for?
A 1-year-old girl with hypotonia and seizures has marked elevations of succinylacetone, α-fetoprotein, and plasma tyrosine; liver ultrasound shows hepatomegaly with nodules. What is the treatment of choice to prevent progression?
A 13-year-old with a history of cardiomyopathy and recurrent episodes of muscle weakness is diagnosed with systemic primary carnitine deficiency. Which organ system involvement is a typical feature?
A 14-month-old boy presents with coarse facial features, corneal clouding, hepatosplenomegaly, joint contractures, and progressive developmental regression. Enzyme testing reveals markedly deficient alpha-L-iduronidase activity, and urine glycosaminoglycans show elevated dermatan and heparan sulfate. What is the most likely diagnosis?
A 2-year-old with poor growth and developmental delay also exhibits severe hypotonia during fasting, hypoketotic hypoglycemia, hepatomegaly, and massive dicarboxylic aciduria. Which diagnosis is most likely?
A toddler has severe abdominal pain, vomiting, and muscle weakness after fasting overnight. Physical exam reveals hepatomegaly, and labs show hypoglycemia with elevated lactate and uric acid levels. What condition is most likely?
A 5-month-old infant is found to have profound hypotonia (“floppy baby”), poor feeding, macroglossia, and hepatomegaly. Echocardiogram reveals marked left ventricular hypertrophy with a thickened interventricular septum. Creatine kinase is markedly elevated, but there is no fasting hypoglycemia or lactic acidosis. Which diagnosis is most likely?
A teenager has arrhythmia, osteoporosis, and high plasma homocysteine/methionine with low cysteine despite vitamin B6 therapy. Which adjunct can improve the biochemical abnormality?
A 7-year-old boy presents with acute abdominal pain, constipation, and muscle weakness. Urinary porphobilinogen is markedly elevated during the episode. Which diagnosis is most likely?
