In cats, the most common eosinophilic dermatoses are feline miliary dermatitis and eosinophilic granuloma complex. The most commonly identified underlying cause is a hypersensitivity reaction. Few cases of familial forms of eosinophilic dermatoses are reported in the literature. Two young adult cats from the same litter presented 2 years apart with a severe and chronic fluid or tissue infiltration of the distal part of several limbs. Lesions started on the forelegs and developed on the other limbs. Cytological and histopathological examinations showed lesions consistent with an atypical form of feline eosinophilic dermatosis associated with secondary bacterial infection. In both cats, antibiotics combined with immunosuppressive treatment partially improved the lesions, which continued to progress on a waxing and waning course, even in the absence of treatment. Allergy work-up did not permit the identification of an underlying allergic triggering factor. The severity of the lesions, the unusual presentation and the unsatisfactory response to immunosuppressive therapy in two feline littermates suggested a genetic form of eosinophilic dermatosis.