There are several causes of non-inflammatory alopecia in the cat. In this species alopecia is usually seen in large, sometimes confluent patches. With exception of the self-inflicted alopecias, hairs are usually easily epilated, and differentiating the underlying cause is often difficult. Following a list of differential diagnoses. In bold letters non-inflammatory alopecias, which will discussed in this lecture. The remaining forms of alopecia are due to infectious, parasitic or allergic causes and are considered inflammatory alopecias.
Self inflicted: allergy, psychogenic
Infection/infestation: dermatophytosis, demodicosis
Associated with trauma/injections/topical treatments: injection site alopecia/cicatricial, topical steroid treatment, posttraumatic alopecia (fracture of pelvis, sacrum)
Immune-mediated: sebaceous adenitis, mural lymphocytic folliculitis, alopecia areata
Metabolic: Cushing's disease
Neoplastic: paraneoplastic alopecia, tumour (epitheliotropic lymphoma)/mural folliculitis
This disease is diagnosed in case of a self-inflicted alopecia, when all allergic/parasitic causes have been excluded and when the cat has some other behavioural problem. Obsessive compulsive disorders (OCD) derive from species-typical behaviours, such as vocalization, locomotion, and grooming. Behaviours derived from grooming include acral lick dermatitis in the dog and self-licking and hair chewing/pulling in the cat (1). The main cause of OCD is a reactive abnormal behaviour, as an expression of a conflict induced by inappropriate environment or management. If the conflict persists, the behaviour might become repetitive and develop into a stereotypy, be performed out of that context, be generalized to any unfavourable situation or be displayed without any identifiable eliciting stimulus. Stress-induced release of opioid peptides is able to sensitize normal dopaminergic neuronal pathways, which become more easily excited, so that any further arousal is then channeled through these pathways and result in that particular behaviour (2). Endorphins (opioid peptides) might be important in the onset of the behaviour and dopamine may be more involved with the maintenance of the behaviour.
There seems to be a breed predisposition in Siamese, Burmese, Himalayan and Abyssinian cats (3). The clinical appearance is the result of chronic chewing, licking and hair pulling by the cat, which results in alopecia on the middle of the back, perineal, genital areas, medial thighs, ventral abdomen, front legs, shoulder and feet. The skin surface usually shows no lesion, unless traumatized by the tongue. The excessive licking can be accompanied by other symptoms, such as a rippling motion of the skin over the back, periodic unexplained states of agitation, a glazed appearance of the eyes with semidilated fixed pupils. The microscopic examination of the hair (broken tips), the application of an Elizabethan collar and the exclusion of all pruritic causes of self-licking (allergies, parasites) lead to the diagnosis. Therapy is based on identification and removal of the stress cause, supported by the use of psychotropic drugs.
1. Antianxiety drugs: amitriptyline (5 mg PO BID), diazepam (1-2 mg PO BID or SID)
2. Drugs that specifically interfere with the neurologic pathways involved in stereotypies: opiate-receptor blockers and dopamine antagonists (4):
a. opiate-receptor blockers: naloxone (1 mg/kg SC once) (naltrexone, nalmefene, diprenorphine) competitively inhibit ß-endorphin receptors, and seem to be more effective in short-term stereotypies (<1 year)
b. dopamine antagonist haloperidol (1 mg/kg PO SID initially, then taper), yields a better effect if the stereotypy exists for a longer period (> 1 year).
3. Drugs that selectively inhibit the serotonin re-uptake: fluoxetine (1 mg/kg SID), clomipramine (1,25-2,5 mg PO SID), imipramine.
4. Other drugs, such as sedatives and tranquilizers are ineffective.
Patches of alopecia may be seen due to iatrogenic causes in the following situations:
local smear of steroid containing cream (temporary alopecia)
injection of steroids subcutaneously (usually temporary, may be associated to thinning of the skin)
cicatricial patch of alopecia following a subcutaneous injection (usually preceded by granuloma, crust and ulceration at the injection site).
An anecdotal report (5) of alopecic patches on the lumbar area arising several weeks after a traumatic event involving the sacrum or pelvic bones. The alopecic patch remains for some months, after which the hair may regrow devoid of pigment. The cause of the alopecia is unknown, probably depending on a deficit of trophic innervation/vascularization.
Clinically cats present with patchy alopecia, easily epilated hair and various amounts of erythema, scales, follicular casts and pruritus. The definitive diagnosis is obtained only with a skin biopsy. A (pio)granulomatous infiltrate invades the sebaceous glands (6). Therapy is based on the use of immunesuppressing drugs (prednisolone 2-4 mg/kg daily, then taper to 1 mg/kg EOD), cyclosporine, or retinoids. In some cases there may be a systemic underlying disease.
Alopecia areata (AA) and pseudopelade
This rare disease is characterized by patchy (AA) to diffuse (Pseudopelade), usually non-inflammatory non-pruritic alopecia (7). The diagnosis is histological. In alopecia areata lymphocytes invade the bulbus and in pseudopelade the isthmic region. AA may spontaneously regress. Therapy (immunesuppressive drugs) is usually not attempted or not effective.
Mural lymphocytic folliculitis
Mural lymphocytic folliculitis (sometimes associated to follicular mucinosis) has a variable clinical picture, from mild alopecic patches, to severe hair loss and desquamation, erythema and variable amounts of pruritus. It is possible that this histologic pattern reflects several different diseases: initial epitheliotropic lymphoma, drug reaction, sebaceous adenitis, dermatophytosis, demodicosis, pseudopelade, FIV infection and even food allergy (8). The severity of the clinical picture and the prognosis depend on the etiology. Idiopathic forms of mural lymphocytic folliculitis have been described in middle aged to old cats (9). Therapy with steroids and/or retinoids may be useful. Cyclosporin may be a valid alternative. Prognosis is not favourable in severely affected animals.
Both iatrogenic and spontaneous Cushing's disease are rare in cats. Clinical signs are similar to those of dogs, whit the exception of polyuria and polydypsia, which are usually absent. Cutaneous lesions include patchy alopecia, easily epilated hair, dry seborrhea with dull hair, and in some cases increased fragility of the skin, which can be torn with minor traction. Description of the diagnostic and therapeutic means for feline Cushing's disease is beyond the scope of this lecture.
This is rarely seen in cats affected by pancreatic carcinoma or, less frequently, bile duct adenocarcinoma (10, 11). The cats are usually systemically ill, they do not eat, present with vomit, diarrhea, lethargy and weight loss. Results of biochemical blood analysis are usually within normal range. Radiographs and ultrasound usually fail to identify the tumour. The alopecia usually starts on the abdomen and legs and can involve the periocular areas and the pinnae. The hair is easily epilated and leaves a typically smooth shiny skin. In some cases there is pruritus and excessive licking, which exacerbates the alopecia. The footpads may be smooth, shiny or fissured and crusted. A Malassezia infection may be seen in the clawbeds (12). Histologically, there is profound atrophy and miniaturization of hair follicles and mild hyperkeratotic hyperplasia of the epidermis, with occasionally a mild lymphocytic exocytosis. The prognosis is usually poor. There are only two cases in the literature, when after surgical resection of the tumour the hair grew back (13, 14). In one of these, the alopecia recurred with relapse of the carcinoma.
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3. Sawyer LS et al. Psychogenic alopecia in cats: 11 cases (19931996). J Am Vet Med Assoc 214:71, 1999.
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6. Scott DW. Adenite sébacée pyogranulomateuse stérile chez un chat. Point Vét. 21:107, 1989.
7. Power HT et al. Novel feline alopecia areata-like dermatosis. Cytotoxic T lymphocytes target the follicular isthmus. In: kwochka KW. et al (eds): Advances in Veterinary Dermatology Vol 3. Butterworth-Heinemann, Boston, 1998:538.
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9. Declerq J. Lymphocytic mural folliculitis in two cats. Vlaams Diergeneeskd Tijdschr 64:177, 1995
10. Brooks et al. Pancreatic paraneoplastic alopecia in 3 cats. J AM Anim Hosp Assoc 30:557, 1994
11. Pascal Tenorio A et al. Paraneoplastic alopecia associated with internal malignancies in the cat. Vet Derm 8: 47, 1997.
12. Godfrey DR. A case of paraneoplastic alopecia with secondary Malassezia-associated dermatitis. J Small Anim Pract39:394, 1985
13. Hodson S et al. Resolution of paraneoplastic alopecia following surgical removal of a pancreatic carcinoma in a cat. Proceedings ESVD/ECVD, 14: 107, 1997
14. Tasker S. et al. Resolution of paraneoplastic alopecia following surgical removal of pancreatic carcinoma in a cat. J Small Anim Pract 40:16, 1999.