- See:
- Osteomalacia:
- Vit D Abnormalities:
- Discussion:
- rickets is an osteomalacic syndrome in which there is an inability to mineralize chondroid and osteoid;
- lack of available calcium or phosphorus (or both) for mineralization of newly formed osteoid;
- osseous changes in both adults and children reflect that either ionized Ca or phos, or both, is insufficient in concentration to mineralize the skeleton fully;
- there is less mineralized bone per unit volume of bone;
- osseous changes in the rapidly growing skeleton of a young child w/ rickets may result in bowing deformities due to the decreased resistance of the
skeleton to bending and shearing moments;
- as consequence, stress frxs w/ resultant deformities occur;
- note that the classic changes of rickets will typically occur in children younger than 6-7 years of age;
- Causes of Rickets and Osteomalacia
- deficiency states
- gastrointestinal causes
- renal osteodystrophy
- hypophosphatemic vitamin d-resistant rickets;
- vitamin-D deficiet rickets:
- may see hypophosphatemia, low level of vitamin D, and normal level of PTH hormone;
- vit D dependent rickets: type I and II
- idiopathic hypophosphatemic rickets:
- new syndrome of hypophosphatemic rickets has been described that is unusual in that symptoms include hyper-calciuria and a normal serum calcium level;
- high 1,25 vit D levels & hyperabsorption of Ca distinguish this new disorder from more common X linked familial hypophos-phatemic rickets, in which
defective 1,25 Vit D production is usual feature;
- it is probably that both X linked and hypophosphatemic forms have a similar renal tubular defect in phosphate reabsorption;
- renal tubular acidosis:
- increased phosphate retention causes increased binding of Ca in the gut;
- patients get a secondary hyperparathyroidism;
- tumors: (see soft tissue and bone tumors)
- may present as late onset rickets in a patient without family history of metabolic disease;
- many of these tumors secrete phosphatonin, which will inhibit tubular resorption of phosphate and which converts hydroxylation of 25 Vit D to 1-25 Vit D;
- medications:
- chronic use of anticonvulsant medication:
- lasix, heparin, steroids, INH, tetracycline;
- Differential Dx:
- hypophosphatasia:
- it is important to note that in young children hypophosphatasia may cause hypercalcemia, and therefore it would be inappropriate to prescribe Vit D or
calcium supplementation (which might be given if the condition was mistaken for rickets);
- metaphyseal chondrodysplasia:
- many pts initially to have been considered to have Vit D resistant rickets, have actually been found to have metaphyseal chondrodysplasia,
& has led to innappropriate administration of vitamin D in some patients;
- fibrous dysplasia or neurofibromatosis:
- fanconi syndrome:
- autosomal recessive syndrome w/ a hypokalemic, hyperchloremic acidosis;
- patients show hypocalcemia, hypophosphatemia, and increase alk phos;
- urine is alkaline instead of being acidotic;
- Clinical Presentation:
- classically brittle bones w/ physeal cupping/widening, bowing of long bones, transverse radiolucent (Looser's) lines, ligamentous laxity, flattening of skull,
enlargment of the costal cartilages (rachitic rosary), and dorsal kyphosis characterize this disorder;
- personality:
- children may show apathy and irritability;
- they may be hypokinetic and may prefer to sit rather than to stand or to walk;
- growth disturbance:
- most children who have florid rickets, regardless of etiology, have some stunting of growth, and the height sometimes falls far below the normal range;
- face and skull:
- skull in very young children may show softening (craniotabes) and prominence of suture lines (hot-cross-bun skull) and frontal bones (frontal bossing);
- defects of the dental enamel and extensive caries are common;
- spine and thorax:
- exam of spine frequently shows a thoracic kyphosis (rachitic cat-back)
- exam of thorax may show prominence of the costochondral junctions (rachitic rosary) and, not uncommonly, pectus carinatum;
- indentation of lower part of the rib cage, at the insertion of diaphragm, is referred to as Harrison groove.
- the resultant deformities may cause a "pot belly" abdominal deformity;
- extremities:
- examination of extremities is likely to show rather marked enlargement of the wrists, ankles,
knees, and elbows and bowing deformity of long bones, especially of the lower limbs.
- see: coxa vara and genu varum;
- frxs are common in children w/ rickets and in those with renal osteodystrophy;
- slipped capital femoral epiphysis is sometimes a serious problem;
- Histologic Changes in Rickets:
- Treatment:
- if disorder is detected early in life, skeleton may develope normally;
- treatment w/ phosphate and 1,25 Vit D can usually maintain normal growth in such disorders as sex linked dominant hypophosphatemic rickets;
- prevention:
- premature infants: require 2,000 IU/day for first 3 months;
- full term infants: require 400 IU/day
- treatment:
- vitamin D 1,500 to 5,000 IU/day for 6-10 weeks;
- w/ in 2-4 weeks, x-rays demonstrate evidence of healing
Principles and results of corrective lower limb osteotomies for patients with vitamin D-resistant hypophosphatemic rickets.