This question tests understanding of inherited metabolic and single-gene disorders. These disorders often result from specific genetic mutations affecting metabolic pathways. In this vignette, the patient presents with elevated phenylalanine on newborn screen, which is indicative of phenylketonuria. The correct choice is A because it accurately explains the genetic mutation involved, leading to prevention of neurologic injury through diet. A common distractor is D which is incorrect because waiting for symptoms risks irreversible damage. Teaching strategies: Encourage students to focus on recognizing patterns in genetic mutations and their biochemical consequences. Practice with case studies to reinforce understanding of inheritance patterns and clinical presentations.

This question tests understanding of inherited metabolic and single-gene disorders. These disorders often result from specific genetic mutations affecting metabolic pathways. In this vignette, the patient presents with acute chest pain, anemia, and sickled erythrocytes, which is indicative of sickle cell disease. The correct choice is B because it accurately explains the genetic mutation involved, leading to codominant expression where carriers are asymptomatic but homozygotes have disease. A common distractor is A which is incorrect because sickle cell is recessive, not dominant with variable penetrance. Teaching strategies: Encourage students to focus on recognizing patterns in genetic mutations and their biochemical consequences. Practice with case studies to reinforce understanding of inheritance patterns and clinical presentations.

This question tests understanding of inherited metabolic and single-gene disorders. These disorders often result from specific genetic mutations affecting metabolic pathways. In this vignette, the patient presents with elevated phenylalanine and low tyrosine, which is indicative of phenylketonuria. The correct choice is A because it accurately explains the genetic mutation involved, leading to neurotoxic buildup. A common distractor is B which is incorrect because it confuses with albinism or other tyrosine defects. Teaching strategies: Encourage students to focus on recognizing patterns in genetic mutations and their biochemical consequences. Practice with case studies to reinforce understanding of inheritance patterns and clinical presentations.

This question tests understanding of inherited metabolic and single-gene disorders. These disorders often result from specific genetic mutations affecting metabolic pathways. In this vignette, the patient presents with recurrent vaso-occlusive crises and anemia, which is indicative of sickle cell disease. The correct choice is A because it accurately explains the genetic mutation involved, leading to sickling under hypoxia. A common distractor is C which is incorrect because it describes hereditary spherocytosis. Teaching strategies: Encourage students to focus on recognizing patterns in genetic mutations and their biochemical consequences. Practice with case studies to reinforce understanding of inheritance patterns and clinical presentations.

The patient's presentation of chorea, psychiatric disturbances, and a family history consistent with autosomal dominant inheritance is classic for Huntington disease. This neurodegenerative disorder is caused by an expansion of a CAG (cytosine-adenine-guanine) trinucleotide repeat in the huntingtin (HTT) gene, leading to a toxic gain-of-function protein. The atrophy of the caudate nucleus is a characteristic imaging finding.

This patient's presentation of meconium ileus, recurrent pulmonary infections, and failure to thrive, along with an elevated sweat chloride test, is diagnostic of cystic fibrosis (CF). CF is an autosomal recessive disorder caused by mutations in the CFTR gene. The most common mutation (ΔF508) leads to misfolding of the CFTR protein, a chloride channel, which is then targeted for premature degradation in the proteasome, preventing its insertion into the cell membrane.

This patient's constellation of findings, including tall stature, arachnodactyly (long, thin extremities), pectus excavatum, and myopia, is classic for Marfan syndrome. This is an autosomal dominant connective tissue disorder caused by mutations in the FBN1 gene, which encodes fibrillin-1. Fibrillin-1 is a key component of microfibrils, which form the scaffold for elastic fibers. Aortic root dilation and dissection are major cardiovascular risks.

The scenario describes phenylketonuria (PKU), an autosomal recessive disorder caused by a deficiency of phenylalanine hydroxylase. This enzyme converts phenylalanine to tyrosine. Without it, phenylalanine accumulates and is converted to phenylketones, which are neurotoxic. The musty odor is due to these metabolites. Treatment involves lifelong dietary restriction of phenylalanine.

This is a classic presentation of G6PD deficiency, an X-linked recessive disorder. The enzyme G6PD is crucial for the pentose phosphate pathway, which produces NADPH. NADPH is necessary to keep glutathione reduced, protecting red blood cells from oxidative damage. Triggers like certain drugs (e.g., sulfonamides), infections, or fava beans cause oxidative stress, leading to hemolysis in deficient individuals. Heinz bodies are aggregates of denatured hemoglobin.

The presence of tendon xanthomas and markedly elevated LDL cholesterol in the context of a family history of premature cardiovascular disease is characteristic of familial hypercholesterolemia (FH). This autosomal dominant disorder is most commonly caused by mutations in the LDL receptor gene, leading to a decreased number of functional receptors on hepatocytes. This impairs the clearance of LDL from the circulation, resulting in severe hypercholesterolemia and accelerated atherosclerosis.