Seborrhea

Introduction

Seborrhea is characterised by a defect in keratinisation or cornification. This results in increased scale formation, a greasy skin and hair coat and often secondary inflammation and infection.

There are large amounts of free fatty acids and cholesterol and decreased amounts of diester waxes in surface lipids which lead bacterial populations to become pathogenic coagulase positive staphylococci

It is a chronic disease affecting mainly dogs, but also sometimes cats and horses.

Primary idiopathic seborrhea

This is a common inherited skin disorder seen most frequently in Cocker Spaniels. Basal epidermal cells in affected dogs undergo accelerated cellular proliferation and turnover.

There is an increase in the number of actively dividing basal cells, a shortened cell cycle, and a decreased transit time to the stratum corneum (7-8 days compared with 21-23 days). Hair follicles and sebaceous glands are also affected.

• Microscopically:
  • Hyperkeratosis distending follicular ostia causing papillary appearance
  • Parakeratosis at edges of follicular ostia
  • Congested, oedematous dermal papillae
  • Spongiotic epidermis with leukocytes

Secondary seborrhea

• Develops secondarily to many types of disease (e.g. ectoparasites, fungal infections, endocrine disease, internal disease or allergy)
• Microscopically:
  • Hyperkeratosis and/or parakeratosis of follicles and epidermis
  • Lesions relevant to the other disease