<prompt> A 1-month old baby presents with frequent vomiting and failure to thrive. There are features of moderate dehydration. Blood sodium is 122 mEq1 and potassium is 6.1 mEq1. The most likely diagnosis is:11 -bhydroxylase deficiencyCriterman syndromeBater syndrome21 -hydroxylase deficiency  <response>: Congenital adrenal hyperplasia due to 21-hydroxylase deficiency 21-OH CAH, in all its forms, accounts for over 95 of diagnosed cases of congenital adrenal hyperplasia. Hence CAH in most contexts refers to 21-hydroxylase deficiency. Ref: Kliegman, Behrman, Jenson, Stanton 2008, Chapter 577, Congenital Adrenal Hyperplasia, In the book, Nelsons Textbook of Pediatrics, Volume 2, 18th Edition, New Delhi, Page 2360; Harrisons Internal Medicine, 17th Edition, Page 2267. 