Oh sure -- I go on a bike ride with the club and to the pub after, and you guys need me?! Sorry I was out!

Well, I agree with multiple things here --

1) Could have had a small injury or irritation that started the process. I'm quite interested in the "got an injection and it helped for a bit".. was this a steroid? If so, it's an anti-inflammatory and the area could have been responding to injection, and not irritating the cat for a bit, and therefore he left it alone. So, I'd look into skin scrapings for odd things (mites), and send to lab for culture for ringworm, and also for culture for bacteria. A basic punch biopsy of the area (small 3 to 5mm ring of skin taken) can help define many of these things at the laboratory. Anything odd turns up, treat it aggressively and see what happens.

2) Yes, most pets do better on 3 than 3.5 limbs. But, as you said, 7 yrs old and suddenly something has changed.

3) Yes, many cats will over-groom with stress or boredom. Yours may just have an easy time getting to this area instead of the belly, rear limbs, etc. Try a plug-in of a relaxing hormone (your vet should be able to get you this -- I admit, I cannot remember the name of it now). But it comes in a spray and a plug-in, and emits calming hormones. Give him more attention and exercise.

4) Try an e-collar (the lampshade) if he is getting the area raw.

5) Any change in diet / environment that could be irritating the skin? They can have many allergies to stuff they come in contact with or stuff they breathe or eat. Make sure all is the same.

6) Treat for fleas NO MATTER WHAT. Flea allergies can be hard to diagnose, and it's easy to treat just in case. DO NOT use the over-the-counter spot treatments such as Sargeants or Hart's, etc. Use Advantage or Frontline -- best out there.

Hope this helps. If all of these are ruled out, (2nd opinion at the dermatology specialist is an excellent idea) and he continues to self mutilate, then amputation is your last option. I would worry that he could still mutilate the stump, although it would be almost flush with the body wall, so less likely to cause trouble. But the habit is still there -- self grooming like this can release endorphins in the brain, making the habit very hard to get rid of. Sort of like our exercise habits!

Good luck and keep us informed!
Jes