Sebaceous adenitis in a dog

Skin biopsies have been taken from areas of scaling and crusting on the dorsal neck and trunk regions of a 2-year-old female poodle.

Fig 1. There is a nodular dermal inflammatory infiltrate (arrow) that corresponds to the location of the sebaceous glands. In many of the sections however, the sebaceous glands are absent.
Fig 2. The inflammatory infiltrate is dominated by macrophages mixed with fewer neutrophils. Rare remaining sebaceous gland cells are identified (delineated by red circular outline).
Fig 3. There is orthokeratotic hyperkeratosis and follicular plugging that manifests clinically as increased scale and follicular casts.

Final Diagnosis

Granulomatous sebaceous adenitis associated with sebaceous gland loss and hyperkeratosis


Sebaceous adenitis is an uncommon lesion in dogs of uncertain aetiology that results in keratinisation abnormalities. The strong breed predilection (e.g. Standard poodles, Akitas, Viszlas and German Shepherds) suggests a genetic basis. Clinically, dogs typically have poor coat quality associated with adherent scale and follicular casts. The lesion distribution is often bilaterally symmetrical but in some cases, the tail can be predominantly affected creating the appearance of a ‘rat tail’.