I'm pretty certain that my husband has onychatrophia judging on the photos I've found online under "nail conditions". It's very difficult to convince him to see a doctor and he has had this condition for the past 10+ years without any medical advice. Not sure if this could be connected; but he has suffered from back problems for the same length of time and has a small patch of psoriasis on his arm which comes and goes.
What Are the Known Causes for Onychatrophia? (photo)
Doctor Answers 1
There are many reasons that one can get Onychatrophia, including other diseases and conditions, or damage to the matrix (the area that your fingernail grows out from). It's best your husband sees a physician for treatment and proper diagnosis. It's impossible to tell you that all of these things are or are not related. But if he does have psoriasis, there's a chance that he has the condition in his nails too, which is very common.
"This answer has been solicited without seeing this patient and cannot be held as true medical advice, but only opinion. Seek in-person treatment with a trained medical professional for appropriate care."