Well, it could be mites, dry skin, or allergies. Because of the pattern, though, I'd suspect psychogenic alopecia - the medical name for licking oneself bald due to a behavioral disorder, obsessive/compulsive disorder (OCD). Most of these cats begin licking their hind legs, tails, and belly raw first. Looks like peach fuzz! Some cats even make themselves bleed because of their raw tongue going over and over the now bald skin. Then this can result in a skin infection, like staph, which is itchy, and it snowballs.
I've had three cats with obsessive/compulsive disorder leading to alopecia. Two went on Prozac, as stress reduction did not help, and their behavior lasted for months. They were back to normal in a few months, and the medication was discontinued. The other's case was due to grief - her best kitty friend died. She went through stress-induced alopecia for about three months but returned to normal as the grief began to resolve.
One other thing that comes to mind is hyperasthesia, or "rolling skin syndrome". It's a condition that's not very well known. It's related to a seizure disorder in some cats, in others it's due to overexposure poisoning from everyday substances like plastic dishes, hairspray, smoke, etc. There are other causes, too, but nearly all cases appear to have no known cause.
It causes extreme skin sensitivity, generally on the tail and hind quarters. The cat may overgroom and cause baldness, have twitching skin, become agitated...some cats have it so severely they will actually chew their tails until they bleed. It also can result in howling, running about wildly, hiding, aggression, and even hallucinations.
Many drugs have been tried and have been successful in some cases. They include antianxiety drugs like Prozac, Valium, Buspar, and amitriptyline, anti-inflammatory agents, like Prednisone, and many others. Those cases believed to be caused by overexposure can be helped by avoiding the causes - using only stainless steel food bowls, feeding foods with no preservatives, not using nail polish, paint, or other products with harmful fumes, and smoking outside (if you smoke).