A 4-month-old male infant presents with recurrent seizures, sparse kinky hair with hypopigmentation, and failure to thrive. Serum copper is 20 microgram/dL (low) and ceruloplasmin is undetectable, despite normal dietary copper intake. The defect lies in:

• A Incorporation of copper into ceruloplasmin within hepatocytes
• B ATP7A-mediated copper efflux from intestinal enterocytes ✓
• C ZIP4-mediated apical uptake of zinc in the duodenum
• D Biliary excretion of copper via ATP7B

Explanation

Menkes disease (kinky hair disease) results from mutation in ATP7B, the copper-transporting ATPase expressed in enterocytes. Failure of copper efflux across the basolateral membrane blocks absorption, so serum copper and ceruloplasmin are low even with adequate intake. ATP7A (option A and D) is the hepatic protein defective in Wilson disease, where copper is high, not low. The X-linked inheritance in an affected male infant supports ATP7B.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.