Skin: idiopathic/granulomatous sebaceous adenitis

Introduction

• Causes : an inflammation of and around the sebaceous glands leading to loss of these structures.
• Signs : dry skin, scaling and hair loss.
• Certain breeds are predisposed, but has been seen in over 60 breeds plus crossbreeds.
• Etiology and pathogenesis unclear.
• Treatment : shampoos, sprays, immunomodulatory therapy and antibacterials.
• Prognosis : guarded but variable.

Diagnosis

Clinical signs

• Fig.1 Skin: sebaceous adenitis 01

  Fig.2 Skin: sebaceous adenitis 02

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  Symmetrical and partial multifocal alopecia with excess scale and dull brittle hairs . (Figs. 1-2)
• Lesions first observed along dorsal midline.
• May affect specific areas - dorsal nasal planum, top of head, dorsal neck, trunk and tail.
• Initially non pruritic, may not progress beyond this stage.
• Progression results in the formation of tightly adherent silver-white scale, follicular casts around hair shafts, and small tufts of matted hair.
• Predisposed to secondary bacterial folliculitis at this stage.

• Fig.3 Sebaceous adenitis 01
  Lesions begin as annular, or arciform, areas of scaling and alopecia predominantly on trunk (Fig. 3).
• Affected areas enlarge peripherally, to become polycyclic, and occasionally coalesce.
• Fine, white non-adherent scale.
• Secondary pyoderma uncommon.

Differential diagnosis

• Other causes of pyoderma [Skin: bacterial skin disease - overview].
• Demodicosis [Skin: demodectic mange].
• Dermatophytosis .
• Sterile granuloma/pyogranuloma syndrome.
• Leishmaniosis .

• Keratinization defects .
• Endocrine skin disease (later stage of disease).

Outcomes

Prognosis

• Response to therapy varies somewhat, depending on the severity or chronicity of the disease and on the breed of animal.
• Prognosis is poorest when sebaceous glands have been completely destroyed.
• Evidence suggests that treatment with cyclosporin A, alone or in combination with topical therapy, reduces macrophagic and lymphocytic inflammation and may achieve some regeneration of sebaceous glands.
• Some dogs have cyclic patterns of spontaneous improvement and worsening.