My son was diagnosed through newborn screening. He began treatment at 7 days old. His only sign of a problem during that first week was weight loss. His 17OHP was 40,000ng/dl, potassium 7.1 (with normal range of 4.1-5.3), sodium 126 (with normal range of 137-147).

When he was about 2 yrs old we had genetic testing done - confirming a diagnosis of SW CAH (21 hydroxylase deficiency)

Hope that helps.