Superficial pyoderma

Superficial pyoderma is defined as an infection confined to the epidermis of the skin. It encompasses feline diseases such as acne and juvenile pustular dermatitis, as well as superficial folliculitis. Superficial pyoderma are under-recognised in cats, probably because of the variant forms which it presents clinically, compared to the more classic signs in dogs.

The predominant lesion types are crusted papules, plaques, scaling, excoriations and ulcerations. It is commonly caused by infection with Staphylococcus spp, although other bacteria may be present[1]S. intermedius appears to be the most common isolate in cats affected with pyoderma.

Superficial infections begin with bacteria normally present in the skin, or are transferred to the affected region by the grooming behaviour of cats. What triggers super-infection with a limited number of specific bacteria is unknown in cats, although it is likely to be multi-factorial. Pre-existing systemic diseases such as eosinophilic granuloma complex, lymphoma, etc., can lead to immuno-incompetence within the epidermis, resulting in proliferation of particular bacterial species. Staphylococcus are unique in that they produce toxins, enzymes and other factors that aid colonisation and thus disease[2].


Primary superficial pyoderma, other than cat-fight abscesses, are uncommon in cats and in most cases are secondary to concurrent disease (see table below). Cytological examination of smears, cultures, histopathology and response to treatment should be used to diagnose and assess the role of bacterial infections in most cases.

Type Appearance Causes
Superficial Papules, crusted papules, plaques, crusting, excoriations, comedones, hyper-pigmentation, scaling, alopecia, ulceration, epidermal collarettes Parasitic: Cheyletiella sppPediculosisNotoedres sppSarcoptes sppDemodex spp
Infectious: Ringworm, FHV, Pox virus, Leishmania spp
Hypersensitivity: Flea allergy dermatitis, Atopy, Food allergy dermatitis, Mosquito-bite hypersensitivity
Autoimmune: Pemphigus foliaceous, bullous pemphigoid
Immune-mediated: Lupus erythematosus, erythema multiforme, exfoliative dermatitis associated with thymoma
Deep pyoderma Non-healing abscesses, cellulitis, nodules, draining fistulae, ulceration Bacterial: Mycobacterium sppNocardia sppActinobacillus sppActinomyces sppRhodococcus equi infection, Staphylococcus spp, Streptococcal spp, or Pseudomonas pyogranuloma
Fungal subcutaneous mycoses: phaeohyphomycosis, Pythium spp, dermatophyte or eumycotic mycetoma; systemic mycoses (sporotrichosis, Cryptococcus sppHistoplasma sppBlastomyces sppCoccidioides spp
Viral: Pox virus infection, FHV
Neoplastic: Fibrosarcoma, Squamous cell carcinoma, lymphoma, mast cell tumour
Sterile idiopathic nodular panniculitis


  1. ↑ August, JR (2006) Consultations in feline internal medicine. Vol 5. Elsevier Saunders, Philadelphia. pp:251-259
  2. ↑ Gemmell, CG (1983) Extracellular toxins and enzymes of coagulase-negative staphylococci. In Easmon, CSF & Adlam, C (Eds): Staphylococci and staphylococcal infections. Vol 2. Academic Press, London. pp:809

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