This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Helmet cells are a feature of 
Select and explain. 
A. G6PD deficiency, B. pyruvate kinase deficiency, C. Pyrimidine 5 - nucleotidase, D. Adenylate kinase deficiency
A: G6PD deficiency
Answer: A: G6PD deficiency 
Explanation: Bite cells / Blister cells / Helmet cells - G6PD deficency.