Due to reports in the literature on the frequent occurrence of low bone mass in both adults and children with congenital haemophilia [15,19,31,32,33], the authors analysed the concentrations of selected markers of bone turnover in the venous blood of adult patients with haemophilia A and B. They demonstrated a statistically significant difference in osteocalcin values compared to a healthy control group. Here, BGLAP is linked to hemophilia A.