Richets

Rickets

OBJECTIVES

The learner will be better able to:
1) Explain the principles reflected in the history and discovery of rickets
2) Generate a differential diagnosis given a patient case
3) Describe the distinct features of a radiological image of a patient with rickets
4) Explain factors that influence the incidence of rickets in a given population
5) Identify classic features of rickets given a patient case

INTRODUCTION

Rickets is a childhood condition resulting in soft and/or weak bones. In adults this condition is known as osteomalacia. Rickets is caused by insufficient amounts of vitamin D, calcium or phosphate. Environmental conditions such as limited sunlight exposure decreases the body's own production of vitamin D which can also lead to rickets. Bones that do not calcify properly do not become rigid and bend more easily. This is readily seen in young children with bowed legs since the weight-bearing bones are relatively weaker. However, not all forms of rickets are severe and some children with rickets can present without the typical skeletal phenotype.

EPIDEMIOLOGY

In the United States, rickets is a rare disease. Increased awareness and improved nutrition have greatly decreased the incidence of this disease. Milder forms of the disease continue to exist in persons with inadequate calcium, phosphorous or vitamin D intake. Infants who are breastfed solely as a source of nutrition are at increased risk of developing rickets. Some studies reveal a higher incidence in persons of darker skin pigmentation because the sunlight-dependent vitamin D synthesis is inhibited in these individuals. Another study also points out that decreased dairy consumption may contribute to the mineral deficiency in Nigerian children, leading to increased reports of rickets.

ETIOLOGY

Rickets is caused by an insufficient amount of activated vitamin D during childhood. The active form of vitamin D, calcitriol, acts as a hormone to regulate calcium absorption from the intestine and to regulate levels of calcium and phosphate in the bones. In nutritional deficiencies of vitamin D, the body is unable to regulate calcium and phosphate levels. The body detects low serum levels of calcium and phosphate, stimulating the release of parathyroid hormone (PTH). PTH helps release calcium and phosphate from the bones to the bloodstream. Decreased amounts
of calcium and phosphate do not
allow the bones to calcify properly.

CLINICAL DIAGNOSIS AND MANIFESTATIONS

Bone pain and tenderness are common symptoms associated with rickets. Rickets also leads to an increased tendency towards bone fractures. Skeletal deformities occur because of the inadequate calcification process. These deformities vary in severity and anatomical location. Rickets in the tibia can lead to bowing of the legs. Spinal deformities can lead to scoliosis or kyphosis. An asymmetrical or odd-shaped skull, craniotabes, is also observed in infants with rickets. This is best illustrated along suture lines since the cranial bones do not fuse because of the reducued calcification process. Chest deformities result in a rachitic rosary, caused by an overgrowth of cartilage at the costochondral junction. Respiratory muscles pull on a weakened rib cage and produce an anterior protrusion of the sternum known as a pigeon breast deformity. Dental deformities are also common in young children. Teeth formation is delayed and there are defects in structure. Teeth are weaker and have a higher incidence of dental caries (cavities).

DIFFERENTIAL DIAGNOSIS

Osteomalacia
Osteodystrophy
Hyperparathyroidism
Malnutrition
Malabsorptive disorder
Metaphyseal chondrodysplasia
Renal tubular disorder

TREATMENT

Supplementation with calcium, phosphate or vitamin D will eliminate most symptoms. If severe skeletal deformities develop, orthopedic surgery may be required.

SUMMARY

Rickets is a disorder of mineralization of newly synthesized organic matrix, leading to improper bone formation. Deficiencies in vitamin D, calcium, phosphorous or inadequate exposure to sunlight are the major causes of rickets. Skeletal deformities develop in growing children who remain untreated for extended periods. Tibial involvement produces bowing of the legs. A rachitic rosary develops at the costochondral margin from the overgrowth of cartilage.

REFERENCES

1. Narchi H, El Jamil M, Kulaylat N. Symptomatic rickets in adolescence. Arch Dis Child 2001;84:501-3

2. Harrison HE, Harrison HC: Disorders of calcium and phosphate metabolism in childhood and adolescence. Philadelphia: WB Saunders Co. 1979.

3. Kreiter SR, Schwartz RP, Kirkman HN Jr, Charlton PA, Calikoglu AS, Davenport ML. Nutritional rickets in African American breast-fed infants. J Pediatr. 2000;137:153-157

4. Fuller KE, Casparian JM. Vitamin D: balancing cutaneous and systemic considerations. South Med J. 2001;94:58-64

5. Okonofua F, Gills DS, Alabi ZO, Thomas M, Bell JL, Dandona P. Rickets in Nigerian children: a consequence of calcium malnutrition. Metabolism 1991;40:209-13

6. Juppner H. Receptors for parathyroid hormone and parathyroid hormone-related peptide: exploration of their biological importance. Bone 1999;25:87-90