A cystic fibrosis patient with weakness, numbness, and ataxia due to poor adherence presents with neurological symptoms. Which vitamin deficiency is most likely responsible?

• A. Vitamin A
• B. Vitamin E
• C. Vitamin D
• D. Vitamin K

Answer: (B)

In cystic fibrosis, fat-soluble vitamins (A, D, E, K) can be poorly absorbed because of pancreatic exocrine insufficiency and steatorrhea. When a patient isn’t adhering to fat-soluble vitamin supplementation, the neurological symptoms most strongly point to vitamin E deficiency. Vitamin E helps protect neuronal membranes from oxidative damage and supports the integrity of myelin and neural pathways. Deficiency manifests with a sensory and motor neuropathy, including weakness, numbness, and ataxia from dysfunction of the posterior columns and spinocerebellar tracts.

The other fat-soluble vitamins cause different problems: lacking vitamin A often leads to night blindness and ocular surface disease; lacking vitamin D leads to bone demineralization like rickets or osteomalacia; lacking vitamin K leads to bleeding tendencies. So the neurological presentation in this CF patient aligns best with vitamin E deficiency.