Primary diseases of keratinization are usually manifested by excess scale formation. They are usually genetic diseases and affected patients have a familial history. Diseases of keratinization are characterized by mild to severe, dry to waxy scales. A rancid odor is often present. In fact, the rancid odor is usually due to the secondary bacterial or yeast infections and the fatty acids that are produced by these microorganisms.
Follicular casts are tightly adherent scales around the hair shaft.
Common secondary findings are alopecia, pruritus, erythema, and pyoderma. However, most of the time these cases are complicated by a concurrent pyoderma or Malassezia dermatitis and it is difficult to establish the sequence of events. Most cases are pruritic at time of presentation. In establishing a diagnosis a few factors are important such as the breed, the age of onset, the response to previous antibiotic therapy and the exclusion of other more common diseases. A dog should never be diagnosed with a primary disease of keratinization without a complete diagnostic plan to rule out secondary causes of scaling.