Pachydermoperiostosis (PDP) is a rare genodermatosis, characterized by pachydermia, digital clubbing, periostosis and an excess of affected males. Although an autosomal dominant model with incomplete penetrance and variable expression has been proved, both autosomal recessive and X-linked inheritance have been suggested. However, at present, genetic heterogeneity is not fully supported. The aim of this study is to review the clinical and pedigree data of 68 published PDP families, including 204 patients. This analysis has confirmed an autosomal dominant mutation in 37 families and suggested the existence of an autosomal recessive form in the remaining families. The two forms may differ in clinical severity, intrafamilial variability and prevalence of some features. Additionally, the marked skewed sex ratio could not be easily explained by an X-linked mutation, but alternative explanations (i.e. testosterone promoting proliferation) are discussed.