You are in: eMedicine Specialties > Radiology > PEDIATRICS RicketsArticle Last Updated: Feb 2, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 7
  Author: Rick R van Rijn, MD, PhD, Staff Physician, Department of Radiology, Academic Medical Center Amsterdam Coauthor(s): Kieran McHugh, MBBCh, Honorary Lecturer, The Institute of Child Health; Consultant Pediatric Radiologist, Department of Radiology, Great Ormond Street Hospital for Children, London, UK Editors: Beverly P Wood, MD, MS, PhD, Professor, Departments of Radiology and Pediatrics, Division of Medical Education, Keck School of Medicine, University of Southern California; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; David A Stringer, BSc, MBBS, FRCR, FRCPC, Professor, National University of Singapore; Clinical Director, Diagnostic Imaging, National University Hospital; Head, Diagnostic Imaging, KK Women's and Children's Hospital, Singapore; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington Author and Editor Disclosure Synonyms and related keywords: English disease, osteomalacia, rachitis, vitamin D deficiency, abnormal vitamin D metabolism, scoliosis, craniotabes, bowing of long bones, knock-knees, genu valgum, triradiate pelvis, metaphyseal cupping, metaphyseal widening, metaphyseal spur, widened epiphyseal plates, metaphyseal fraying, metaphyseal splaying, rickets rosary, saber shin deformity INTRODUCTIONSection 2 of 7
  BackgroundRickets is an entity in which mineralization is decreased at the level of the growth plates, resulting in growth retardation and delayed skeletal development. Osteomalacia is found within the same spectrum, affects trabecular bone, and results in undermineralization of osteoid bone. By definition, rickets is found only in children prior to the closure of the growth plates, while osteomalacia occurs in persons of any age. Any child with rickets also has osteomalacia, while the reverse is not necessarily true. The term rickets is said to have derived from the ancient English word wricken, which means "to bend." In several European countries, rickets is also called English disease, a term that appears to stem from the fact that at the turn of the 19th century, rickets was endemic in larger British cities. PathophysiologyRickets results from a Vitamin D deficiency, the abnormal metabolism of vitamin D, or the abnormal metabolism or excretion of inorganic phosphate. Histologic changes are seen at the level of the growth plates or, more specifically, at the level of the hypertrophic zone, where an increased number of disorganized cells is found. The increased number of cells results in increased width and thickness of the hypertrophic zone. Understanding of the pathophysiology of vitamin D–deficiency rickets requires knowledge of the biochemistry of vitamin D (cholecalciferol). What generally is termed vitamin D is actually a prohormone, which requires activation. In the human body, vitamin D can be either exogenous (vitamin D2, acquired through food supplements) or endogenous (vitamin D3, resulting from exposure of the body to sunlight). Activation is accomplished by hydroxylation of vitamin D at 2 sites. The first hydroxylation, at the 25 site on the vitamin D molecule, occurs mainly in the liver, although this process may also occur in the kidneys and intestine. This step in the vitamin D pathway is a self-limiting feedback system, which is necessary because 25-hydroxyvitamin D persists only for several days in the human body, while vitamin D itself can be stored in the liver for months. The second hydroxylation, at the 1 site on the vitamin D molecule, always takes place in the kidneys; this process is regulated by the enzyme 25-hydroxyvitamin D1a-hydroxylase. Only after the second hydroxylation occurs does vitamin D become active (1,25-dihydroxyvitamin D). Activation is regulated by parathyroid hormone (PTH), a potent inhibitor of 25-hydroxyvitamin D1 a-hydroxylase. When PTH is suppressed, 25-hydroxyvitamin D is converted into the much less potent 24,25-dihydroxyvitamin D. The action of 1,25-dihydroxyvitamin D is 2-fold; first, it regulates and enhances absorption of calcium from the intestines, and second, it may stimulate differentiation of stem cells into osteoclasts. Metabolic bone disease of prematurity, seen in infants with very low birthweight (VLBW), can occur in as many as 55% of infants weighing less than 1000 g at birth (Backstrom et al, 1996). In the third trimester of pregnancy, bone mineral density shows the highest rate of increase. In this stage, the requirement for calcium and phosphorus is at its maximum level. If the amount of dietary calcium is too low, renal a-1-hydroxylase is activated and 1,25-dihydroxyvitamin D is generated. This in turn increases the uptake of calcium and phosphorus in the gastrointestinal tract and inhibits the release of PTH. Although PTH reduces the output of phosphorus in urine and decreases bone absorption, the potent bone-absorbing capacities of 1,25-dihydroxyvitamin D leads to a net decrease in bone mass. Therefore, it is of the utmost importance that nutrition be especially adapted in infants with VLBW. In utero, the fetus receives approximately 120-140 mg/kg of calcium and 70-80 mg/kg of phosphorus, but breast milk contains only 60 mg/kg of calcium and 30 mg/kg of phosphorus. It is easy to see that these levels are inadequate and that infants with VLBW need special formula to gain bone mass. (For further discussion, see Backstrom, as well as Disorders of Bone Mineralization, Hypophosphatemic Rickets, and Osteomalacia and Renal Osteodystrophy.) Because rickets results from a metabolic disturbance, the underlying disease should be diagnosed. The causes of rickets can be classified into 11 main categories:
FrequencyUnited StatesIn the Western world, exact data on the prevalence of rickets are hard to find; however, Welch and colleagues (2000) stated that around the year 1900, finding children younger than 2 years who were not affected would have been difficult in urban areas. In the following 50 years, with the introduction of dietary supplements for children, rickets was eradicated almost completely. In the last few years, reports have indicated that the prevalence of rickets has increased. A recent study described 5 cases of vitamin D–deficient rickets in Georgia; in all cases, the child was a black male who was breastfed for more than 6 months without additional vitamin D supplementation (Tomashek, 2001). When the mother has a low vitamin D level, the child can be born with a relative vitamin D deficiency as a result of decreased maternal transfer. In these cases, vitamin D supplementation during pregnancy can increase birthweight and growth. Additionally, the breast milk of a mother with a low vitamin D level will contain less vitamin D than normal, adding to the risk of development of rickets. However, even in mothers with a normal vitamin D level, breastfeeding can cause rickets because the recommended daily vitamin D intake for infants is 200 IU, while breast milk contains only 12-60 IU/L. This has led to the advice to supplement vitamin D when breastfeeding. InternationalIn most developing countries, rickets is seldom seen, supposedly as a result of high exposure to sunlight. An exception occurs in groups of women who are rarely allowed to leave the house (largely for religious reasons) or who must wear veils (chadors) when they do. Because these women may have low vitamin D levels, their babies are at a higher risk of developing rickets. Premature babies: This group is at a relatively high risk of developing rickets. Dabezies and Warren (1997) described a 39% incidence of rickets and an associated 10% fracture incidence in premature infants with VLBW. Mortality/Morbidity
Race
SexBoys and girls are affected equally with rickets. There is a form of genetic rickets, called X-linked hypophosphatemic rickets, in which some children, often girls, may be only moderately affected. However, girls with this disorder can have rickets symptoms that are just as severe as those in boys. Age
AnatomyThe most affected skeletal sites are the anterior costochondral junctions of the middle ribs, the proximal humerus, the distal radius and ulna, the distal femur, and the proximal and distal tibia. Clinical DetailsClinical findings are related to the involved skeletal site.
Preferred ExaminationPlain radiography of the affected bones is the preferred examination. The distal radius and ulna typically demonstrate rachitic lesions early on radiographs. In preterm neonates and young infants, radiographs of the knee may be more reliable than those of the wrist. Limitations of TechniquesIn the early stage of rickets, radiographs depict no pathology; however, chemical changes in blood serum can already be found at this time. DIFFERENTIALSSection 3 of 7
Bone Metastases
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| Media file 1: Anteroposterior and lateral radiographs of the wrist of an 8-year-old boy with rickets demonstrates cupping and fraying of the metaphyseal region. | |
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| Media file 2: Radiographs of the knee of a 3.6-year-old girl with hypophosphatemia depict severe fraying of the metaphysis. | |
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| Media file 3: Radiograph in a 4-year-old girl with rickets depicts bowing of the legs caused by loading. | |
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| Media file 4: Radiograph in a 4-year-old girl with rickets, focused on the knees. Image depicts the development of knock-knees. | |
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| Media file 5: Radiograph of the proximal humerus in a 2.5-year-old girl who had a peripheral neuroectodermal tumor of the right brachial plexus. After treatment with ifosfamide, the patient developed rickets of the proximal femur. In this case, metastasis should be incorporated into the differential diagnosis. | |
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| Media file 6: Radiograph of the knees of an 11-year-old boy with treated vitamin D–resistant rickets. Image demonstrates bilateral multiple growth arrest lines and underdevelopment of the medial aspect of both the tibial plateau and the femoral condyle. | |
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| Media file 7: Radiograph of a leg with the patient in a standing position demonstrates knock-knees. The patient is an 11-year-old boy with treated vitamin D–resistant rickets. | |
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| Media file 8: Findings in patients with rickets. | |
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Article Last Updated: Feb 2, 2007
