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: Pediatrics
2 year old child presented with diarrhoea and failure to thrive, Blood examination shows - Na = 122, K - 6. He is most probably suffering from ? 
Select and explain. 
A. Bater syndrome, B. 214x Hydroxylase deficiency, C. 11-p Hydroxylase deficiency,, D. 17-a Hydroxylase deficiency
B: 214x Hydroxylase deficiency
Answer: B: 214x Hydroxylase deficiency 
Explanation: Ans. is `b' i.e., 21-a Hydroxylase deficiency o Na' is 122 (hyponatremia). That means, there is salt losing enzyme deficiency, causing hyponatremia and hyperkalemia. o 21 hydroxylase deficiency causes hyponatremia and hyperkalemia. 17a-hydroxylase and 11beta hydroxylase deficiency cause hypernateremia and hypokalemia.