Pachydermoperiostosis is a rare osteo-cutaneous disease characterized by hypertrophy of bones and surrounding soft tissues. The cutaneous manifestations include coarsening of facial features, cutis verticis gyrata, digital clubbing, hyperhidrosis and seborrhoea. The pathogenetic mechanism of the disease is still debated, and proposed aetiological factors include genetic influences, anomalies in fibroblast activity, or alteration in peripheral blood flow. We studied a patient with the incomplete form of pachydermoperiostosis, assessing epidermal growth factor receptor (EGF-R) and sex hormone steroid receptors (SR) in the affected skin, and also evaluating the urinary excretion of EGF. The results showed high levels of nuclear steroid receptors, increased cytosolic oestrogen receptors, and no detectable progesterone and androgen cytosolic receptors. EGF-R was also undetectable, and the urinary excretion of EGF was elevated. These findings suggest that the increased tissue sensitivity to circulating sex-steroids could induce enhanced tissue EGF/transforming growth factor alpha (TGF-alpha) production and utilization. The SR-EGF-R system could therefore be involved in determining hypertrophy of the affected tissues.