Mupirocin Pemphigus-Like Drug Reaction in a Dog
Authors: Ferreira Tiago Cunha , De Medeiros Guedes Rodrigo Fonseca , Bezerra Belise Maria Oliveira , Nunes-Pinheiro Diana Célia Sousa 
Published: March 2020

Background: Pharmacodermia is defined as adverse reaction in skin, mucosa and appendages, which generates morpho-functional alterations in cutaneous barrier, inducing autoimmune diseases, such as pemphigus foliaceous, which is known as the most common autoimmune skin disease in dogs. This disease involves autoantibodies against desmoglein and desmocolin molecules, being induced by the use of certain drugs. Mupirocin (pseudomonic acid A) is a broad-spectrum antibiotic with bacteriostatic activity, being effective against Gram-positive pathogens and used to control superficial bacterial folliculitis. Based on that, the aim of this study was to report a pemphigus-like lesions after topical use of mupirocin in dog.Case: An 1-year-old, uncastrated male, Poodle dog, weighing 13.8 kg was treated in a private clinic in Fortaleza. The main complaint was related to pruritus in abdominal and inguinal region, in addition of legs licking. Dermatological examination revealed melanic crusts, epidermal collars and diffuse pustules in inguinal, abdominal, perianal and thoraco-lumbar regions. The therapy was based on topical use of Mupirocin in form of 0.2% aquous spray. After drug administration, the animal presented urticaria, diffuse epidermal collars, papulo-crusted and pustular lesions, which were more evident in abdominal and inguinal region. Nasal erythema, binocular blepharitis, apathy and fever were also observed. Cytological examination and bacterial culture were performed, revealing inflammatory and acantholytic cells and no bacterial growth. Biopsy procedure revealed subcorneal pustule with presence of epithelial acantholytic cells and neutrophils, compatible with canine pemphigus foliaceous. The topical treatment of ocular lesions with 0.1% Tacrolimus associated with systemic treatment with high dose of prednisolone (1.2 mg kg-1). The patient improved the dermatological clinical signs, however, some side effects have already become evident, such as the presence of telangiectasia, polyuria, polyphagia and polydipsia. Heterodox therapy based on the use of azathioprine (2 mg kg-1) was chosen in order to reduce corticoid dose. After 3 days of therapy, blood material was collected for hepatic evaluation, detecting hepatotoxicity. From the results, azathioprine therapy was suspended, and only high-dose corticosteroid therapy (1.5 mg kg-1) was maintained. The patient presented a considerable improvement in the lesion after 10 days of treatment.Discussion: There have been reports that pharmacodermic reactions may be associated with the development of autoimmune diseases, such as pemphigus foliaceus and vulgaris. In some cases, the lesions regress after drug discontination. In others, the medication acts as a triggering factor, activating the genetic predisposition of patient, which develops the pathology even after therapy interruption. The drug related pemphigus-foliaceous is a well-recognized disease in humans, however this disease is limited to sporadic cases in dogs. The therapy was based in use of a high dose of prednisolone, which caused some side effects. Therefore, a heterodox therapy was chosen in order to reduce the corticoid dosage. At the first hemato-biochemical evaluation, the patient already presented significant alterations, being requested to suspend the prescribed treatment, although the owners already reported improvement of the dermatological lesions. Due to this, a higher dose of prednisolone was chosen, obtaining the best response among the therapies used since the beginning of the treatment. After clinical improvement, the gradual reduction of steroidal therapy was started in order to avoid side effects related to suppression of the hypothalamic-pituitary-adrenal axis. This report provides evidences of Mupirocin as a potential triggering factor of pemphigus-like lesions in dogs.