Clinical, histopathological and genetic features of a cutaneous adnexal polycystic syndrome in Lykoi cats: a prospective study of 10 cases

ObjectivesThe Lykoi is a recently recognised feline breed with a unique coat phenotype caused by six variants of the Hairless (<i>HR</i>) gene. A specific severe cutaneous comedonal syndrome has been reported in this breed. The aim of the study was to carry out a clinical, histopathological and genetic characterisation of this syndrome.MethodsProspective data collection included clinical evaluation, skin biopsies for histopathology, trichoscopic examination of hair shafts, blood sampling for haematology and biochemistry, cutaneous swabs for bacteriological culture, and buccal swabs for DNA extraction and genotyping.ResultsIn total, 11 privately owned Lykoi cats were enrolled, including those with varying degrees of skin involvement and one healthy cat. Cats were aged 1.5-7 years at the time of diagnosis. Clinical presentation was characterised by papular lesions and comedones, ranging from severe generalised forms (n = 6/10) to moderate regional forms (n = 2/10) and to mild scattered forms (n = 2/10). Histopathological lesions from skin biopsies revealed infundibular follicular cysts (n = 9/10), sebaceous gland (duct) cysts (n = 10/10) and sweat gland cysts (n = 5/10). Genetic analysis identified 5/6 described <i>HR</i> variants among the 10 affected Lykoi and the control Lykoi.Conclusions and relevanceThis cutaneous syndrome shows a variable clinical severity that is not fully explained by genotype alone. The consistent presence of cysts from all three adnexal structures, even in clinically unaffected skin, supports the recognition of a novel skin condition, which we propose to name cutaneous adnexal polycystic syndrome (CAPS) in Lykoi cats. Further research is needed to elucidate its pathogenesis.