Full Professor of the Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, Dermatology Service Av. Prof. Dr. Orlando Marques de Paiva, São Paulo
Among the most intriguing and remarkable feline dermatopathies challenging veterinary medicine are those known as psychogenic dermatitis (PD). The occurrence of feline PDs fluctuates, in each analyzed country (Brazil, France and United States), from 1.2 to 4.7% (Nesbitt, 1982; Ledon and Larsson, 1990; Otsuka and Larsson, 1996; Bourdeau and Fer, 2004). A survey in a specialized service of dermatology unit in São Paulo, Brazil, in an eight-year period (between 1999 and 2007), appraise that, among 1,236 attended cats, about 3% (n=37) of the cases reported symptoms of PD. These diseases add up to the seventh main cause of integumentary diseases in domestic cats (Oliveira et al., 2008), but it is safe to assume that many veterinarians overestimate the occurrence of these diseases. Waiglass et al. (2006) reported in Canada, from 21 cats initially diagnosed with psychogenic alopecia, one of the diseases grouped as PDs, only 2 (10%) of the cases unarguably had psychogenic etiology. In 16 (76%) of those felines the fur-pulling (trichotillomania) was imputable to other causes.
Nowadays, mainly in human dermatology, the branch of medicine denominated psychodermatology (Estelita-Lins et al., 2008), which studies the mutuality between skin and mind, has been receiving increased attention. The correlation between the integument and the central nervous system (CNS) has in fact been studied since the 18th and 19th centuries, in the works of Falconer (1708), Damon (1891), Bloch (1895) and Kaposi (1895). The mind-skin correlation is partly explained by the fact that the epidermis and the nervous system stem from the same embryonic layer, the ectoderm. Psychodermatology, in human or veterinary medicine, supports that the diseased skin should not be considered by itself, but as part of the patient as a whole--that is, a complex and integral subject, exposed to a variety of causes that superimpose, intermingle, add up and interact among themselves. To study and diagnose psychogenic skin diseases, one must adopt a bidirectional view of the mind-body relations, abolishing the infectious etiology approach of trying to define single causes to a disorder, however well-adapted they may seem. It should be favored, instead, a multi-factor model, as adopted in degenerative, neoplastic and psychiatric diseases diagnosis.
The International Statistical Classification of Diseases and Related Health Problems (ICD-10) lists and categorizes about 54 psychiatric disorders that could develop psychodermatological symptoms (Estelita-Lins et al., 2008). In 1997, Fitzpatrick et al. proposed a classification of human diseases with psychodermatological aspects, clustering them in three groups: I. Conditions with major psychic influences or psychiatric comorbidity (trichotillomania, factitial dermatitis, neurotic excoriation, deliria); II. Conditions showing evidences of psychic origin (vitiligo, universal or generalized pruritus, alopecia areata); III. Conditions produced by stress or emotional imbalance (seborrheic and atopic dermatitis).
Experienced veterinarians can safely avouch that such classification can fully be transposed to the integumentary diseases afflicting pets, especially nowadays, when cats and dogs closely coexist with their owners. Six years ago, VIRGA (2003), in an excellent study on behavioral dermatology, classified the behavior-connected dermatitis in four categories of phenomena: psychophysiologic disorders (PD), primary (PSD) and secondary behavioral disorders (SBD) and cutaneous sensory disorders (CSD). The PDs constitute the primary dermatologic conditions that are affected by emotional stress, and includes the atopic dermatitis and chronic inflammatory dermatoses. "With PD, the activation of psychoneuroendocrinoimmunologic mediators may contribute to an exacerbation of clinical signs. By means of vasoactive mediators, emotional stress can precipitate or perpetuated the 'itch-scratch cycle' associated with PD. Potential environmental and social stressors that should be considered are as follows: inadequate mental and aerobic stimulation or exercise, inadequate interaction with family or other pets, social isolation, conflicts (status or territorially-related), addition or loss of family members or pets, new home/environment, boarding or hospitalization. The conditions for which the primary problem is related to behavior in nature and the secondary skin manifestations are self-induced are classified as PBD. The PBD in cats include compulsive behaviors (psychogenic dermatitis, feline hypersensitivity syndrome, tail suckling and excessive chewing of feet and/or tails), psychogenic alopecia and pruritus (Virga, 2003). Secondary behavior disorders (SBD) "may result from dermatologic conditions that adversely affect the normal behavioral patterns and social functioning of the animal. Based on sensory stimuli (pain and pruritus) typically associated with a variety of dermatologic lesions, it is likely that the behavioral patterns and social functioning of animals may be affected". The cutaneous sensory disorders (CSD) are "conditions for which the patient experiences a purely sensory complaint without clinical evidence of a dermatologic, neurologic or medical condition. As such, although it is problematic to confirm a diagnosis in animals, CSD should be carefully considered if the patient exhibits: a response as if experiencing pain to non-noxious stimuli (touch, mild pressure, heat or cold); a markedly exaggerated response to a stimulus that is typically painful; behaviors that subjectively seem to be in response to or avoidance of an unpleasant stimulus or, finally, excessive self-directed behavior (e.g., licking, grooming, chewing, biting, rubbing)". The anamnesis is of utmost relevance, as should be, according to Virga (2003) and Scott et al. (2001), a detailed behavioral background, including: description of the behavior before, during and after the problem; chronology and progression (continual or sporadic); investigation of the home environment (including relations to humans and other animals) and if the occurrence of symptoms is related to the presence or absence of those animals or humans); patient's background (adoption sources, familial history, behavior prior to the problem, training); interaction/handling (feeding and grooming) and duration, frequency and for of said interaction; environment (verification of sleeping and resting locales).
The symptoms of the PDs are somewhat typical and can be verified through dermatological examination. They normally consist of elementary skin lesions, alopecia (localized or generalized), pelage color changes (pheo or rhodotrichia), tissue losses (ulceration or excoriation), thickness variations (keratosis, lichenification, plaques). As the self-directed behaviors can have potentially varied and multiple etiologies, clinical examination must be thorough, contemplating both the nervous and integumentary systems, and further examination (blood and urine, biochemical, radiological, and histopathological) should be considered. The topography and aspect of the lesions should be used to eliminate basic causes (perianal lesions could either mean psychogenic alopecia and CSDs or a swollen and inflamed anal sac; ventral abdominal lesions could be caused by psychogenic alopecia and CSDs or by eventual lower urinary tract diseases). If a PD is clearly diagnosed, a veterinarian properly trained or specialized in ethology, conditioning or psychology should introduce modification procedures in the environment and behavior patterns, making use, if necessary, of pharmacological measures, choosing from tri-cyclic antidepressants (amitriptyline, doxepin, clomipramine) or selective serotonin reuptake inhibitors (fluoxetine, paroxetine, sertraline). The professional, however, must be fully aware that each distinct class of medication has several adverse effects, whether to the integumentary system (drug eruptions) or to other systems, including the CNS.