Rickets is a heterogeneous group of diseases of the growing child caused by defect mineralization of bone. Nutritional rickets is caused by deficiency of vitamin D, calcium or both. Several hereditary forms of rickets exist where the disease proceeds into adulthood. Nutritional rickets was common in the past, but by introduction of preventative administration of cod liver oil and vitamin D supplementation, nutritional rickets became a rarity. During the last decades, case reports of nutritional rickets reappear in the industrialized countries. It is the general conception that in the industrialized countries, hereditary rickets is the most prevalent cause of rickets today. However, the incidence of nutritional rickets and the incidence and prevalence of hereditary rickets in Scandinavia are unknown. The most common form of hereditary rickets is hypophosphatemic rickets (HR). The geno- and phenotype among Scandinavian patients have not been characterized. Especially, the disease in adult patients is not well described. Moreover, there are conflicting reports of the benefits of medical treatment throughout childhood, and in addition on gender differences in disease severity.