Skin biopsy and autoimmune diseases

What it involves

A skin biopsy is the taking of a small piece of skin — usually with a punch 4–8 mm in diameter, or by wedge excision — and sending it to a histopathology laboratory, where a pathologist examines the tissue structure under the microscope. Unlike cytology, it shows not only cells but also their arrangement in the layers of the skin, which makes it possible to diagnose diseases that cannot otherwise be told apart.

Autoimmune skin diseases are a group in which the immune system attacks the skin's own cells: pemphigus foliaceus, discoid lupus, vascular diseases and others. They look like an “ordinary” infection — scabs, erosions, pustules — but do not respond to antibiotics, and their treatment consists of suppressing the immune system, so the diagnosis must be certain before therapy begins.

A biopsy also provides an answer in unusual hair loss, skin nodules, lesions on the nose and paw pads, and chronic ulcers, and the histopathology result comes back to us with the pathologist's description and suggestions — we discuss it with you and turn it into a treatment plan.

When it is used

We propose a biopsy when skin lesions do not fit typical diseases, do not respond to properly conducted treatment over 4–6 weeks, involve the nose, paw pads, eyelids or the area around the claws, blisters and erosions appear, or when confirmation is needed before starting immunosuppressive medication.

It is worth doing a biopsy early — before steroids or antibiotics change the picture of the tissue. If the animal is already receiving steroids, they usually have to be stopped for 2–3 weeks before sampling, provided its condition allows.

Indications: symptoms that should prompt a visit

• Scabs and erosions have appeared on your dog's nose, and the nose is losing pigment and becoming “smooth”.
• Your cat has scabs on the pinnae, around the claws and on the nipples that do not clear up with an antibiotic.
• There are cracks, scabs or excessive keratinisation on the paw pads, and your dog limps.
• The skin lesions look like an infection, but there are no bacteria on cytology and an antibiotic does not help.
• Your dog is losing hair in an unusual way — in patches, on the nose or on the back — without itching.
• Blisters or ulcers have appeared on the skin, in the mouth or at the junction of skin and mucous membranes.
• A skin nodule or ulcer cannot be clearly assessed by cytology.

Conditions for which we use it in particular

Diagnostics beforehand

Before a biopsy we carry out basic dermatological tests (cytology, scrapings, trichogram) in the on-site laboratory — to rule out simple causes and choose good sampling sites. If a systemic disease is suspected (systemic lupus, vasculitis) we add a full blood count, biochemistry and urinalysis.

The choice of biopsy site determines the value of the result: we take several samples from fresh, typical lesions, not from old, treated scars. If the animal is receiving steroids or antibiotics, we plan sampling after they have been stopped, when that is safe. When sampling under sedation, the pre-anaesthetic assessment according to STD-01 applies.

How it proceeds

Aftercare

The sampling sites heal in 10–14 days; we fit a collar if the animal licks them. We remove the sutures at a check-up. Call us if the wound opens, becomes red or begins to discharge.

We go through the result at a follow-up visit — we explain what the pathologist found and agree the treatment. Autoimmune diseases require long-term treatment with regular check-ups and blood tests; we reduce drug doses gradually to the lowest effective dose, and relapses are possible and require the plan to be adjusted.

Frequently asked questions