A 22-year-old woman is diagnosed with bipolar disorder. Over the next year, she develops neurologic manifestations that include resting and intention tremors, rigidity, chorea, dysphagia, and dysarthria. On physical examination, she has bilateral Babinski signs. There are ring-like deposits of green material involving the cornea bilaterally, but her vision is not decreased. One year later, she has an illness that lasts 3 weeks, with nausea, vomiting, and malaise and scleral icterus. Laboratory findings include serum AST, 100 U/L; ALT, 122 U/L; alkaline phosphatase, 105 U/L; total bilirubin, 4.5 mg/ dL; glucose, 77 mg/dL; and creatinine, 0.9 mg/dL. Serologic test results for hepatitis A, B, and C are negative. This episode subsides without treatment, but she eventually develops cirrhosis. A mutation in a gene encoding for what substance is most likely to be present in this woman?
A 22-year-old woman is diagnosed with bipolar disorder. Over the next year, she develops neurologic manifestations that include resting and intention tremors, rigidity, chorea, dysphagia, and dysarthria. On physical examination, she has bilateral Babinski signs. There are ring-like deposits of green material involving the cornea bilaterally, but her vision is not decreased. One year later, she has an illness that lasts 3 weeks, with nausea, vomiting, and malaise and scleral icterus. Laboratory findings include serum AST, 100 U/L; ALT, 122 U/L; alkaline phosphatase, 105 U/L; total bilirubin, 4.5 mg/ dL; glucose, 77 mg/dL; and creatinine, 0.9 mg/dL. Serologic test results for hepatitis A, B, and C are negative. This episode subsides without treatment, but she eventually develops cirrhosis. A mutation in a gene encoding for what substance is most likely to be present in this woman?
π‘ Explanation
**Core Concept**
The patient's symptoms suggest a systemic disorder involving the nervous system, liver, and cornea, leading to a diagnosis of Wilson's disease, an inherited disorder of copper metabolism.
**Why the Correct Answer is Right**
Wilson's disease is caused by a mutation in the ATP7B gene, which encodes a copper-transporting P-type ATPase responsible for incorporating copper into ceruloplasmin and excreting excess copper into bile. The patient's symptoms, including neurological manifestations (tremors, rigidity, chorea, dysphagia, and dysarthria), Kayser-Fleischer rings (ring-like deposits of green material involving the cornea), and liver dysfunction (cirrhosis), are characteristic of Wilson's disease. The patient's episode of acute illness with jaundice and liver enzyme elevation is consistent with acute liver failure, which can occur in Wilson's disease.
**Why Each Wrong Option is Incorrect**
**Option A:** A mutation in the HFE gene is associated with hereditary hemochromatosis, a disorder of iron metabolism, not copper metabolism.
**Option B:** A mutation in the ALA gene is associated with hereditary porphyria, a disorder of heme biosynthesis, not copper metabolism.
**Option C:** A mutation in the APOC3 gene is associated with hypertriglyceridemia, a disorder of lipid metabolism, not copper metabolism.
**Clinical Pearl / High-Yield Fact**
Wilson's disease can be diagnosed by measuring serum ceruloplasmin levels, which are typically low in affected individuals. However, a definitive diagnosis requires genetic testing for mutations in the ATP7B gene.
**Correct Answer:** C. A mutation in a gene encoding for ceruloplasmin (the ATP7B gene) is most likely to be present in this woman.
β Correct Answer: C. C Copper-transporting ATPase
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