Rickets: The Skeletal Disorders of Impaired Calcium or Phosphate Availability

Rickets and osteomalacia result from inadequate mineralization of growing or mature bone due to insufficient calcium and/or phosphate availability. Rickets refers to the histological, radiographic, and clinical abnormalities that occur in the physis (growth plate) leading to skeletal deformities (particularly of the lower extremities), impaired linear growth, and abnormal gross motor function. Osteomalacia is not limited to the growth plate and is characterized by undermineralized bone matrix and can be present before or after skeletal maturity when physes are fused. The most common cause of rickets worldwide is nutritional deficiency of vitamin D and/or calcium. Genetic forms of rickets are rare and result from abnormalities in the pathways regulating calcium, vitamin D, and phosphate homeostasis. This chapter will outline the pathophysiology, etiology, clinical evaluation, and treatment of nutritional and heritable forms of rickets.