JPC SYSTEMIC PATHOLOGY
Signalment (JPC #2812885-01): Military working dog
HISTORY: None provided
HISTOPATHOLOGIC DESCRIPTION: Haired skin: Multifocally expanding the dermis there are densely cellular areas of inflammatory cells centered on ruptured hair follicles and free hair shafts (furunculosis). Inflammatory nodules are composed of viable and degenerate neutrophils, lymphocytes, plasma cells, and macrophages. Adjacent, less affected hair follicles are markedly elongated, ectatic and distorted (follicular dysplasia), lined by hyperplastic epithelium, and filled with lamellated keratin debris and fragmented hair shafts admixed with degenerate neutrophilis and basophilic colonies of 1um cocci (luminal folliculitis). Adjacent apocrine gland ducts are multifocally ectatic, filled with an eosinophilic homogenous material (inspissated secretory product) and surrounded by aggregates of lymphocytes and plasma cells (perihidradenitis). Throughout the superficial and deep dermis dysplastic hair follicles and ectatic apocrine glands are embedded in abundant collagen (fibrosis) composed of dense bands that widely separate adnexa and which often orient perpendicular to the epidermis (vertical streaking). Within the superficial dermis, there are scattered melanomacrophages and free melanin granules (pigmentary incontinence). Diffusely, the overlying epidermis is moderately hyperplastic with acanthosis, prominent anastomosing rete ridges and compact orthokeratotic hyperkeratosis. Multifocally, there is deposition of melanin granules in all layers of the epidermis (hyperpigmentation).
MORPHOLOGIC DIAGNOSIS: Haired skin: Furunculosis, pyogranulomatous, multifocal, marked, with apocrine perihidradenitis, dermal fibrosis and vertical streaking, epidermal and follicular hyperplasia, and orthokeratosis, breed unspecified, canine.
CONDITION: Acral lick dermatitis
SYNONYMS: Acral lick granuloma, acral pruritic nodule, neurodermatitis
- Common syndrome characterized by incessant licking resulting in self-mutilation
- Seen in male > female dogs, but can occur in either sex of any breed
- Most commonly seen in large active-breed dogs < 5-year-old
- Predisposed breeds: Doberman pinscher, German shepherd dog, great Dane, Labrador retriever, Irish setter and golden retriever
- Multifactorial, often categorized as a primary behavioral dermatosis (e.g. obsessive-compulsive disorder, boredom, separation anxiety) +/- underlying organic disease (e.g. hypersensitivity reaction, bacterial or fungal infection, demodicosis, trauma, joint disease, neoplasia, or neuropathy)
- Endorphin release during licking may propagate the itch-lick cycle
- May lead to secondary deep pyoderma, further perpetuating clinical signs
- Often there is secondary traumatic furunculosis (displaced free hair shafts deep to follicle)
TYPICAL CLINICAL FINDINGS:
- Persistent licking and chewing, most common on the cranial aspect of the distal forelimb (carpus, metacarpus, radius) > hindlimbs (tibia and metatarsus)
TYPICAL GROSS FINDINGS:
- Ovoid, firm, well-circumscribed, 2-6 cm diameter alopecic plaque
- +/- ulcerated center surrounded by a hyperpigmented halo
- +/- saliva staining of surrounding hair
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Epidermis: marked acanthosis and rete ridge formation and compact orthokeratotic and/or parakeratotic hyperkeratosis
- Vertical alignment of collagen between rete ridges (vertical streaking)
- Follicles: infundibular elongation and enlargement (ectasia), folliculitis, furunculosis
- Epitrichial glands: epithelial cell hypertrophy, gland dilation, retention or inspissation of secretions, hidradenitis/perihidradenitis, rupture
- Dermis: superficial +/- deep fibrosis with vertical streaking of collagen and capillaries, lymphoplasmacytic dermatitis
ADDITIONAL DIAGNOSTIC TESTS:
- Bacterial culture: deep cultures yield Staphylococcus intermedius most commonly, with occasional isolates of methicillin-resistant Staphylococcus species; cytology and superficial cultures (Micrococcus, Proteus mirabilis, Pseudomonas spp.) do not correlate well with deep culture results
- For gross and/or histopathological findings: deep pyoderma, bacterial furunculosis, fungal granulomas, dermatophytosis, demodicosis, neoplasia
- Other psychogenic disorders in dogs: tail biting (young, long-tailed, long-haired); tail dock neuroma (nerve nodule, Cocker spaniel); flank sucking (Doberman pinscher); self-nursing (females); anal licking (poodle); foot licking (atopy, Malassezia)
- Cats: psychogenic alopecia and dermatitis (excessive grooming, anxiety);
- Most common in indoor cats and oriental breeds;
- Two clinical forms
- Psychogenic dermatitis: lesion grossly resemble that of eosinophilic plaque
- Alopecic form: regional hypotrichosis and normal skin
- Tail sucking (Siamese)
- Horse: equine self-mutilation syndrome
- No primary lesion, but secondary excoriation may be present
- First calf heifer: excessive licking of udder and teats, sometimes lead to teat necrosis and culling
- Denerolle P, White SD, Taylor TS, et. al. Organic diseases mimicking acral lick dermatitis in six dogs. J Am Anim Hosp Assoc. 2007;43(4):215-220.
- Mauldin EA, Peters-Kennedy J, et. al. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:561-562.
- Gross TL, Ihrke PJ, Walder EJ, et. al. Hyperplastic diseases of the epidermis. In: Gross TL, Ihrke PJ, Walder EJ, et. al., eds. Skin Diseases of the Dog and Cat. 2nd ed. Ames, IA: Blackwell Science Ltd; 2005:140-142, 429.
- Hargis AM, Ginn, PE. The integument. In: Zachary JF, McGavin MD, eds. Pathologic Basis of Veterinary Disease. 5th ed. St. Louis, MO: Elsevier Mosby; 2012:1018-1019.
- Campbell KL, Griffin CE, Miller WH, eds. Small Animal Dermatology. 7th ed. Philadelphia, PA: WB Saunders Company; 2013:650-658.
- Shumaker AK, Angus JC, Coyner KS, et. al. Microbiological and histopathological features of canine acral lick dermatitis. Vet Dermatol. 2008;19(5):288-298.