Rickets, or vitamin D deficiency rickets, is a systemic, chronic, nutritional disease characterized by skeletal lesions due to disorders of calcium and phosphorus metabolism caused by vitamin D deficiency in infants, children, and adolescents. The main feature is incomplete calcification of the cartilage plate and bone tissue of the growing long bone epiphysis, and incomplete calcification of mature bone due to insufficient vitamin D. What parents think is calcium deficiency is not really a calcium deficiency, but a lack of vitamin D that causes calcium to not be absorbed properly.