What's wrong with his feet??
By Suzanne Stack, DVM
By far, in greyhounds, the most common reason for multiple nail loss from multiple feet is pemphigus - aka symmetrical lupoid onchodystrophy (SLO). In pemphigus/SLO, the nails separate at the base and come off. You may see normal looking nails and more blood upon losing a nail in newer cases and less blood and "funky nails" in more chronic cases. The nails that regrow are stumpy, crumbly and misshapen.
Pemphigus/SLO as it occurs in the greyhound involves the nails only, there are no other systemic signs though there may certainly be a poor appetite and/or lethargy associated with the chronic pain. All of the greyhound specific texts and articles I've ever read refer to this autoimmune condition as "pemphigus." These sources include "Care of the Racing Greyhound" (Blythe, Gannon, Craig), "Canine Sports Medicine & Surgery" (Bloomberg, Dee, Taylor), and "The Racing Greyhound - Management, Medicine & Surgery" (Herron, Gannon). On the other hand, a biopsy submitted to any commercial lab will be given the diagnosis of "SLO." Properly, as one of the IDEXX pathologists explained it to me, SLO involves nails and so is the correct histopathological diagnosis, whereas pemphigus involves footpads and interdigital skin. So "pemphigus" vs. "SLO" is unimportant and a matter of semantics we are talking about the same clinical syndrome. Those of us who learned our learnings from greyhound texts and authors call it pemphigus, while those newly discovering it may call it SLO. While toenail pemphigus/SLO is an oddball diagnosis in other breeds, it should go straight to the top of the list in greyhounds experiencing multiple nail loss.
While it is, of course, possible to get secondary infections in unhealthy pemphigus nails, you cannot resolve the problem without treating the underlying autoimmune disorder. Too many people spend too much time and money treating pemphigus as a "fungal" (the #1 misdiagnosis) or "bacterial" infection with foot soaks, topicals, and expensive oral medications. Common sense will tell you that culturing a nail as a means of diagnosis is quite likely to yield any number of cooties as greyhounds use their nails to walk across the (unsterile) ground.
Unfortunately, the only way to definitively diagnose pemphigus/SLO is by amputating the whole P3 (end toe bone, including nail, just as you declaw a cat). A pathologist can make the diagnosis only by observing the skin/nail junction. The appearance/course of pemphigus in greyhounds is so classic that I feel it's a real waste of time/money, not to mention unnecessary pain and disfigurement for the poor greyhound, to go through this in the name of proving a diagnosis.
The preferred treatment, as outlined in "Care of the Racing Greyhound", is the following:
Once healthy nails have regrown, it may be possible to wean the dog off of prednisone entirely. Though it takes 4-5 months for new nails to regrow, often there is a dramatic improvement in comfort within the first few weeks of treatment. My experience has been that the sooner you get on top of these, the better the chance for regrowth of normal nails. Chronic untreated pemphigus greyhounds will always have crumbly stumpy nails, but at least treatment even at that point will stop them from continuing to lose nails. It is also worth checking thyroid levels and supplementing greyhounds that are unequivocally low.
There are alternative treatments using a niacinamide (NOT niacin)/tetracycline combination and DermCaps (vitamin E/Omega fatty acid supplement). Worth a try if prednisone scares you, perhaps, but hasn't worked in my experience. Do remember that because nails take a long time to grow, you may waste 4-5 months this route waiting for results that don't happen. Meanwhile, doing the greyhound no favors by withholding prednisone, which is the cornerstone of all autoimmune disease treatment. Please remember that we are talking about a maximum of 15 mg prednisone daily for the first week, tapering to 5 mg every other day for long-term your basic chihuahua pred dose.