Often only at puberty or during a fertility workup.
XX-male (de la Chapelle) syndrome is rare, on the order of 1 in 20,000 to 25,000 male births. Most affected men look typically male at birth, so it usually goes unnoticed until puberty brings signs like gynecomastia, or until a fertility check finds no sperm in the semen — a common consequence, since the missing rest of the Y leaves the testes unable to make sperm.
