Pyogranulomatous mural folliculitis in a cat treated with methimazole

Abstract

An 11-year-old spayed female domestic shorthair cat was presented for polydipsia, hyperactivity and bilateral thyroid gland enlargement. Total T4 (TT4) was in the upper interval range; therefore, an early hyperthyroidism was suspected. A treatment trial with methimazole was started, as the owner refused further tests. Six months later the owner stopped the treatment. One year later, clinical signs persisted and TT4 was still in the upper interval range. Methimazole was re-introduced but 48 h later the cat presented non-pruritic alopecia with erythema, scales and perilesional yellowish crusts. Pyogranulomatous mural folliculitis was diagnosed by histopatological examination of the skin biopsies. Methimazole was withdrawn and macroscopic lesions healed and disappeared histologically in 15 days. An idiosyncratic drug reaction to methimazole was suspected. To the best of our knowledge, this is the first report of feline pyogranulomatous mural folliculitis likely secondary to an adverse drug reaction to methimazole administration.

Presumed Sterile Eosinophilic and Granulomatous Mural Folliculitis and Furunculosis in an Angora and Pygmy Crossbreed Goat

“…Granulomatous mural folliculitis is rarely reported in domestic animals 3,4,7) . This lesion, with prominent multinucleated histiocytic giant cells and eosinophils, has been reported in one other goat with scaling and crusting of the pinnae, nares, and buccal skin 1) . It also had multifocal erythematous papules, particularly on the distal limbs, which progressed to generalized erythema with localized scaling and thinning of the hair coat.…”

“…The etiopathogenesis is unknown in the majority of cases of granulomatous mural folliculitis reported in domestic animals. Adverse cutaneous drug reactions are the most common presumed cause of granulomatous mural folliculitis in dogs [4][5][6][7] , cats 1) , and horses 7) . In the goat reported herein, there was no known history of drug administration, including vaccinations, that closely preceded the onset of skin disease.…”

Granulomatous mural folliculitis in 16 domestic goats: Infection with malignant catarrhal fever viruses and colocalization with ovine herpesvirus-2 using in situ hybridization

“…4,10,11,24,28,44,45 GMF has otherwise been observed with dermatophytosis and presumed idiosyncratic drug reactions associated with L-thyroxine, cefadroxil, and amitraz in dogs, and methimazole in a cat. 3,39,41,42 In the last example, there was complete resolution of skin lesions 15-days following cessation of methimazole administration. 3 Idiopathic GMF has also been recently described in a canine case report, in which stabilization of skin lesions was achieved with combination immunosuppressive therapy.…”

“…3,39,41,42 In the last example, there was complete resolution of skin lesions 15-days following cessation of methimazole administration. 3 Idiopathic GMF has also been recently described in a canine case report, in which stabilization of skin lesions was achieved with combination immunosuppressive therapy. 31 Equine linear alopecia is another idiopathic entity with GMF, clinically characterized by circular areas of alopecia arranged in a linear, vertically-oriented configuration on the neck, shoulders, and/or lateral thorax.…”