You searched for: “onychopathology
onychopathology (s) (noun) (no pl)
The study of disorders of the nails; onychology: Jill read that the outdated term onychopathology, relating to the science of finger and toe nails, was not used any more in the working medical language.

The dermatologist that Mary went to said that the formal discipline of onychopathology did research in the past on the kind of ailment she had regarding her nails becoming dry, yellowish, and cracking.