Feline maculopapular cutaneous mastocytosis: a retrospective study of 13 cases and proposal for a new classification

Abstract

Case series summary Cutaneous mastocytosis is a disorder rarely reported in veterinary dermatology and usually described as 'urticaria pigmentosa'. This study aimed to evaluate the diagnosis, treatment and outcome of 13 affected cats, selected from the files of a private referral dermatology practice within a period of 14 years. Breeds of the affected individuals included Sphynx (n = 9), Devon Rex (n = 2) and Sphynx/Devon Rex crossbreeds (n = 2). Females (n = 9) were over-represented and the median duration of clinical signs prior to diagnosis was 8 months. The clinical presentation of these 13 cats was compared with cases reported in the veterinary literature and classified according to the current human consensus on cutaneous mastocytosis. Three clinical forms could be distinguished in cats: (1) large papular lesions and wheals, typically localised to the head, shoulders, ventral neck and axillae, and which may spontaneously resolve (termed polymorphic maculopapular cutaneous mastocytosis); (2) erythematous dermatitis, characterised by small maculopapular lesions often associated with crusts and with a poorer prognosis (termed monomorphic maculopapular cutaneous mastocytosis); and (3) more chronic dermatitis characterised by lichenification and hyperpigmentation, similar to the human condition 'urticaria pigmentosa' (termed pigmented maculopapular cutaneous mastocytosis). Histopathology was performed in eight cases and revealed a superficial-to-deep dermatitis characterised by infiltrates of mast cells and eosinophils. The response to various treatments, including antihistamines, steroids and ciclosporin, was variable. Relevance and novel information This article reports 13 new cases of feline cutaneous mastocytosis, confirming the clinical presentation and apparent breed predisposition. The feline maculopapular cutaneous mastocytosis seems to be clinically very close to the human form. This study proposes a new classification system for the feline disease based on the current human consensus, clinical presentation and prognosis, with three different subforms: polymorphic maculopapular cutaneous mastocytosis with eventual spontaneous regression; monomorphic maculopapular cutaneous mastocytosis with chronic evolution; and pigmented maculopapular cutaneous mastocytosis.

Cutaneous mastocytosis in a dog

“…8 In cats, different therapies have been recommended with various results, such as antihistamines, glucocorticoids, antibiotics or cyclosporine. 16,17,19 The current case revealed a good response to H1 antihistamine and oral glucocorticoids, similarly to previous reports. 6 Although a complete remission was not verified, a marked improvement and reduction in the number of skin lesions were noted.…”

“…It has been reported as a maculopapular eruption, often associated with significant pruritus and inconsistent hyperpigmentation. [15][16][17] Histopathologic findings are similar between the current case and previous reports, consisting of cutaneous dense aggregates of well-differentiated MC, with fewer number of eosinophils, minimal to mild pleomorphism and rare mitotic figures. 5,7,8 These microscopic features are also similar to the ones described in human UP.…”

“…This suggests that CM may be controlled with oral glucocorticoids and antihistaminic medication and that tapering the dose of glucocorticoids can be considered in cases without disease regression to minimise potential associated side effects. A good response to treatment with oral cyclosporine was seen in some feline reports 17,19 . To the authors’ knowledge, there are no reports in the canine veterinary literature that were treated with this drug.…”

“…The other reported dog did not respond to treatment with H1 and H2 antihistamines and glucocorticoids, but pruritus and flare episodes were completely resolved after treatment with lokivetmab and H1 and H2 blockers 8 . In cats, different therapies have been recommended with various results, such as antihistamines, glucocorticoids, antibiotics or cyclosporine 16,17,19 …”

“…A good response to treatment with oral cyclosporine was seen in some feline reports. 17,19 To the authors' knowledge, there are no reports in the canine veterinary literature that were treated with this drug. If effective in dogs, cyclosporine may be an interesting option, which can potentially replace or lead to a dose reduction in the treatment with glucocorticoids.…”