A list of feline diseases which results in some hair loss. There is a page on hair loss in cats also. The source1 is excellent.
“It is good for a cat caretaker to know a bit about cat health but only as a tool to help instruct their veterinarian”
Hyperthyroidism [Link] – excess of thyroid hormone. The hair of about 33% of cats with hyperthyroidism pulls out easily. There is also hair loss.
Hypothyroidism [link]- deficiency of thyroid hormone. This is uncommon. The hair is brittle and dull, skin is dry. The hair coat thins out.
Psychogenic alopecia – compulsive over-grooming. Hair thins in a stripe down the back and/or on abdomen.
Feline endocrine alopecia [link]- symmetrical thinning, balding of the coat on the insides of the hind legs, genital area and lower abdomen. Mainly affects neutered/spayed males/females.
Ringworm [link]- a fungal infection. Highly contagious disease and transmission to people is common. Can be hard to see in a cat and diagnose and treat, as I understand it. Skin has scaly, red circular or partially circular patches where there is hair loss. Sometimes there are just broken hairs around the face and ears.
Stud tail – excess of secretions from “supra-caudal gland“ at the base of the tail. Greasy, bad smelling “waxy-brown material”. There might be no hair where the gland is.
Demodectic mange – uncommon in cats. Loss of hair and thinning around eyes and eyelids. Cat looks “moth-eaten”.
Cortisone excess – seen with Cushing’s disease. Hair loss symmetrically over body and trunk. Underlying skin darkens. May be a thyroid problem also. Skin may thin.
Congenital hypotrichosis – a genetic condition. Kittens lose their hair by 4 months of age.
Indolent ulcer [link]- usually concerns middle of upper lip. Shiny red patches of hairless skin.
Eosinophilic granuloma – I’ll have quote the source information for this rare disease, “raised, red circular plaque on the abdomen or insides of the thighs or linear plaques on the backs of the hind legs. (note: plaque in medical terms in this context means: an abnormal patch on the skin)
1. Source: Cat Owner’s Home Veterinary Handbook third edition, page 131.