Beware the Diagnosis of Psychogenic Alopecia

By Jennifer Coates, DVM on Jan. 23, 2013

Recently, I was doing some research for another article when I stumbled upon this intriguing study: “Underlying medical conditions in cats with presumptive psychogenic alopecia.”

Okay, "intriguing" might be a little over the top, but diagnosing a cat with psychogenic alopecia always leaves a bad taste in my mouth. In essence I’m saying, "I can’t figure out why your cat is pulling out her hair, so let’s call her crazy."

The word "psychogenic" means originating from a psychological rather than physical cause, and "alopecia" simply means hair loss. As should be obvious, before a veterinarian diagnosis a cat with psychogenic alopecia he or she should rule out every other cause for the patient’s condition. Cats can over-groom themselves to the point of hair loss for all sorts of reasons; for example, parasites, infections, allergies, adverse food reactions, pain, and hormonal disorders.

In the real world, many owners allow their vets to run a few tests and if the answer is not forthcoming they basically say, "I don’t really care why my cat’s pulling her hair out, just make her stop." Whenever I back into a diagnosis of psychogenic alopecia in this way, I always have the sneaking suspicion that if I had just been allowed to run one more test (okay, to be honest it might have taken three or four) I could have figured out what was really going on. Essentially, the results of this study prove just that.

The scientists reevaluated 21 cats that had been presumptively diagnosed with psychogenic alopecia. The cat’s primary caregiver filled out a detailed behavior and dermatologic questionnaire, and a veterinarian performed a complete behavioral and dermatologic examination and then ran the following tests:

cytologic examination of skin scrapings
fungal culture
evaluation of responses to parasiticides
a food trial with an exclusion diet; if the cat didn’t respond it was treated with a steroid injection to rule out itchiness as a cause of over-grooming
assessment for environmental allergies and hormonal disorders
histologic examination of skin biopsy specimens

Here’s what the study found:

Medical causes of pruritus [itchiness] were identified in 16 (76%) cats. Only 2 (10%) cats were found to have only psychogenic alopecia, and an additional 3 (14%) cats had a combination of psychogenic alopecia and a medical cause of pruritus. An adverse food reaction was diagnosed in 12 (57%) cats and was suspected in an additional 2. All cats with histologic evidence of inflammation in skin biopsy specimens were determined to have a medical condition, but of 6 cats without histologic abnormalities, 4 had an adverse food reaction, atopy[environmental allergy], or a combination of the 2, and only 2 had psychogenic alopecia.

The take home message? Failing to run a complete diagnostic work-up on a cat that is pulling her hair out is an invitation for a misdiagnosis.