Moderate severity

Pemphigus Foliaceus

The most common autoimmune skin disease of cats, in which the immune system attacks the glue holding skin cells together, producing crusts and pustules on the face, ears and paw pads.

⚠️ Common symptoms

Yellow crusts and scabs on the bridge of the nose, ears and around the eyesCrusting and thickening of the paw pads, sometimes with lamenessPustules around the nail beds with a cheesy dischargeHair loss over affected areasItching, which is variable but can be intenseFever, lethargy and reduced appetite in widespread cases

Pemphigus foliaceus is uncommon, but among the autoimmune diseases of feline skin it is the one vets see most. The name comes from the Greek for "blister" and the Latin for "leafy" — a reference to the flaky, leaf-like crusts that peel from affected skin.

The distribution is what makes it recognisable. It goes for the face first: the bridge of the nose, the margins and inner surfaces of the ears, and the skin around the eyes develop pustules that are so fragile they are rarely seen intact, having already burst and dried into thick yellow-brown crusts by the time the cat is examined. The paw pads are the other classic site, and crusting around the nail folds — often with a soft, pale, cheesy material that can be squeezed out — is close to being a signature of the disease in cats. Owners sometimes bring a cat in because it has started walking oddly rather than because of the skin, the pads being too sore to bear weight comfortably.

Because the clinical picture overlaps heavily with ringworm, bacterial pyoderma, allergic dermatitis and even some forms of cutaneous lymphoma, a diagnosis cannot be made by looking. Skin biopsies are essential; the pathologist looks for acantholytic keratinocytes — rounded-off skin cells that have lost their connections to their neighbours and float free in the pustule. Cytology from an intact pustule can be strongly suggestive and is often done first because it is quick and cheap.

Treatment is a balancing act. Enough immunosuppression to stop the antibody attack, but not so much that the cat becomes vulnerable to infection or develops steroid-induced diabetes. Most vets induce remission with a relatively high steroid dose over two to four weeks, then taper in careful steps with regular rechecks, adding a steroid-sparing drug if the required maintenance dose stays uncomfortably high. Cats generally tolerate this better than dogs do, and the prognosis is considerably better than the frightening early appearance suggests: the great majority achieve good control and live comfortable, ordinary lives, with flares managed by temporarily increasing the dose.

One practical point is worth emphasising for owners. If the disease appeared shortly after starting a new medication — methimazole for an overactive thyroid is the classic example — tell your vet, because drug-triggered pemphigus can remit permanently once the drug is stopped and an alternative found.

🔍 Causes

Pemphigus foliaceus is an autoimmune disease: antibodies target desmosomes, the protein rivets that bind neighbouring skin cells together. When those connections fail, cells separate and fluid-filled pustules form just beneath the outer layer of skin, which quickly rupture and dry into the characteristic honey-coloured crusts. Most feline cases are idiopathic, with no trigger identified. A minority are drug-induced — methimazole for hyperthyroidism, some antibiotics and topical flea products have all been implicated — and these can resolve when the drug is withdrawn. Chronic skin inflammation from allergy is a suspected trigger in some cats.

🛡 Prevention

There is no way to prevent idiopathic pemphigus. Where a drug reaction is suspected, note the medication and never re-expose the cat. Keeping a written record of any drug that preceded a skin flare is genuinely useful. Good flea control and management of underlying allergy reduce the background inflammation that may contribute in some cases.

💊 Treatment

Diagnosis requires a skin biopsy, and treatment is immunosuppression. Corticosteroids — usually prednisolone or triamcinolone — are the first line, given at high doses to gain control and then tapered slowly to the lowest dose that keeps the disease quiet. Cats that cannot be controlled on steroids alone, or that develop side effects such as diabetes, are given a second agent such as ciclosporin or chlorambucil. Secondary bacterial infection of the crusted skin is treated with antibiotics, and gentle bathing softens and lifts crusts. Most cats need lifelong medication, though a proportion can eventually be weaned off entirely.

When to see a vet: Any crusting rash on a cat's face, ears or paw pads deserves veterinary assessment — it can look very like ringworm, allergy or a bacterial infection, and the treatments are completely different, so guessing is unhelpful and treating pemphigus as an infection will not work. See a vet urgently if the cat is also lethargic, feverish, off its food, or is limping on crusted pads.

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⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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