Systemic disease of infancy and childhood in which calcification of growing skeletal elements is defective because of a deficiency of vitamin D in the diet or a lack of exposure to ultraviolet radiation (sunshine).
Most common in premature infants and usually develops between 6 and 12 months of age.
Classic radiographic signs :
It include cupping and fraying of metaphyseal ends of bone with disappearance of normally sharp metaphyseal lines; delayed appearance of epiphyseal ossification centers, which have blurred margins (unlike the sharp outlines in scurvy); and excessive osteoid tissue in the sternal ends of ribs producing characteristic beading (rachitic rosary).
(A) Initial film shows severe metaphyseal changes involving the distal femurs and proximal tibias and fibulas. Note the pronounced demineralization of the epiphyseal ossification centers.
(B) After vitamin D therapy, there is remineralization of the metaphyses and an almost normal appearance of the epiphyseal ossification centers.