- Risk Factors
- Rickets is a bone disorder caused by a deficiency of vitamin D, calcium, or phosphate.
- There are several different types of rickets.
- There are different bony abnormalities associated with rickets, but all are due to poor mineralization with calcium and phosphate.
- The active form of vitamin D is synthesized by skin cells when exposed to sunlight.
- Vitamin D is found in small amounts in some foods.
- Infants who are exclusively breastfed should receive vitamin D supplements.
- Children and adolescents who do not obtain enough vitamin D though milk and foods should receive vitamin D supplements.
What is rickets?
Rickets is a bone disorder caused by a deficiency of vitamin D, calcium, or phosphate. Rickets leads to softening and weakening of the bones and is seen most commonly in children 6-24 months of age. There are several subtypes of rickets, including hypophosphatemic rickets (vitamin-D-resistant rickets), renal or kidney rickets (renal osteodystrophy), and most commonly, nutritional rickets (caused by dietary deficiency of vitamin D, calcium, or phosphate). Classic nutritional rickets is also medically termed osteomalacia.
What is the history of rickets?
Roman descriptions of individuals with rickets can be found as early as the second century, and in the 1640s, the condition was well documented as a common bone ailment across England. Unfortunately, the scientifically proven cause of rickets was not identified until the 1920s, and by the 1930s, public-health initiatives recommended fortifying milk with vitamin D and cod-liver oil as a nutritional supplement for young infants and children. This led to a near eradication of rickets in the United States and other industrialized nations. Unfortunately, rickets has made a comeback and is still common in less-developed nations. Moreover, for a variety of reasons, rickets is seen more frequently amongst infants and children living in industrialized nations, often among more affluent populations.
What are risk factors for the development of rickets?
Rickets risk factors include
- premature birth (low levels of vitamin D, calcium, and phosphorus);
- limited sun exposure (especially in high and low latitudes);
- hereditary metabolic diseases (for example, X-linked hypophosphotemic rickets);
- darkly pigmented individuals;
- infants born to vitamin D-deficient mothers;
- renal (kidney) diseases that affect calcium and phosphorus absorption; and
- nutrition -- suboptimal calcium and phosphorus intake or low vitamin D intake (seen in certain vegan diets due to avoidance of milk/dairy products). Soy milk and breakfast cereals fortified with vitamin D are helpful.
What causes rickets?
Regardless of the type of rickets, the cause is always either due to a deficiency of vitamin D, calcium, or phosphate. Three common causes of rickets include nutritional rickets, hypophosphatemic rickets, and renal rickets.
Nutritional rickets, also called osteomalacia, is a condition caused by vitamin D deficiency. Vitamin D is a fat-soluble vitamin that is essential for the normal formation of bones and teeth and necessary for the appropriate absorption of calcium and phosphorus from the bowels. It occurs naturally in very small quantities in some foods such as saltwater fish (salmon, sardines, herring, and fish-liver oils). Vitamin D is also naturally synthesized by skin cells in response to sunlight exposure. It is necessary for the appropriate absorption of calcium from the gut.
Infants and children most at risk for developing nutritional rickets include dark-skinned infants, exclusively breastfed infants, and infants who are born to mothers who are vitamin D deficient. In addition, older children who are kept out of direct sunlight or who have vegan diets may also be at risk.
Hypophosphatemic rickets is caused by chronically low levels of phosphate in the blood. The bones become painfully soft and pliable. This is caused by a genetic dominant X-linked defect in the ability for the kidneys to control the amount of phosphate excreted in the urine. The individual affected is able to absorb phosphate and calcium from the gut, but the phosphate is lost through the kidneys into the urine. This is not caused by a vitamin D deficiency. Patients with hypophosphatemic rickets typically have obvious symptoms by 1 year of age. Treatment is generally through nutritional supplements of phosphate and calcitriol (the activated form of vitamin D).
Renal (kidney) rickets
Similar to hypophosphatemic rickets, renal rickets is caused by a number of kidney disorders. Individuals suffering from kidney disease often have decreased ability to regulate the amounts of electrolytes lost in the urine. This includes calcium and phosphate, and therefore the affected individuals develop symptoms almost identical to severe nutritional rickets. Treatment of the underlying kidney problem and nutritional supplementation are recommended for these patients.
What are rickets symptoms and signs?
Signs and symptoms of rickets include bone pain or tenderness, dental deformities, delayed formation of teeth, decreased muscle strength, predisposition to infections, impaired growth, short stature, and a number of skeletal deformities, including abnormally shaped skull (craniotabes), bowlegs, rib-cage abnormalities (rachitic rosary), and breastbone, pelvic, and spinal deformities.
Occasionally, in very severe rickets, patients may develop even more serious signs and symptoms associated with very low levels of calcium or phosphate. These might include tetany (involuntary muscle contractions) or seizures. These are medical emergencies and require immediate treatment.
Who are the specialists who treat rickets?
Pediatricians and family practitioners usually care for children with nutritional rickets without consulting specialists. Kidney specialists (nephrologists) generally help manage renal rickets as well as hypophosphatemic rickets and sometimes a pediatric endocrinologist (specializes in hormones) may get involved.
How do health care professionals diagnose rickets?
Rickets is initially diagnosed clinically with a complete medical and nutritional history and with a complete physical exam by a health professional. If rickets is suspected in a child and the child has no acute symptoms such as seizures or tetany, X-rays of long bones (radius, ulna, and femur) and ribs are obtained.
Vitamin D levels, alkaline phosphatase, parathyroid hormone (hormone involved in calcium and phosphate control), and electrolytes, including indirect measurements of kidney function (BUN and creatinine), should be evaluated if the X-rays show any of the following characteristics that are consistent with rickets:
- Widening or abnormally shaped metaphysis (most actively growing part of the bone below the growth plate)
- Obvious bowing of the femurs
- Osteopenia (bones which are not as dense, a sign of decreased mineralization)
- Rib flaring (rachitic rosary)
- Multiple fractures at different healing stages
Different causes of rickets will reveal different findings on laboratory tests. For the scope of this article, we will focus on vitamin D deficiency. In these cases, the active form of vitamin D will be decreased, parathyroid hormone will be increased, and calcium and phosphate will be decreased.
What is the treatment for rickets?
The treatment for rickets depends upon the cause as mentioned above in the discussion of hypophosphatemic rickets and renal rickets. In cases of nutritional rickets and vitamin D deficiency, treatment is simple. The first step is to prevent the complications of calcium and phosphate deficiency by correcting any abnormal levels with supplemental calcium or phosphate as well as the activated vitamin D (calcitriol). Once the diagnosis of rickets is confirmed, initiation of vitamin D supplementation is recommended, as well as a diet rich in calcium. This is especially important for children on vegan diets. The treatment for some of the bony abnormalities depends on the severity of the cases and may require referral to an orthopedic provider for evaluation.
What is the prognosis for rickets?
Outcomes for children with nutritional rickets are excellent, especially if diagnosed early. Appropriate supplementation with calcium and vitamin D will lead to healing of the bony defects within days to months. Severe bowing, seen in longer-standing cases of rickets, may also resolve over a number years without requiring surgical intervention. In patients with very advanced disease, however, the bony changes may be permanent.
Is it possible to prevent rickets?
Pediatricians, family practitioners, and obstetricians are responsible for educating parents (and expecting parents) about measures to prevent rickets. For the expecting mother, this includes recommending prenatal vitamins and appropriate nutritional counseling. For the new mother, it is important for her to be advised about vitamin D supplementation for exclusively breastfed babies and, as the child gets older and begins to wean, appropriate nutritional counseling, and reasonable sun exposure for the child.
Vitamin D insufficiency is increasingly being recognized as an under-detected health risk for people of all ages in the United States. Up to 30% of U.S. children are vitamin D deficient to some degree and worldwide this is a much higher percentage. In 2011, the American Academy of Pediatrics (AAP) published a technical report titled "UV Radiation: A Hazard to Children and Adolescents" that concluded that all "infants, children, and adolescents receive vitamin D supplementation and avoid overexposure to sunlight and artificial sources due to the health risks (cancer, etc)." Currently, studies are unclear about how much vitamin D is enough in certain populations, but the current recommendation is for at least 400 IU daily.
Given the fact that vitamin D supplementation may not be readily available worldwide, more research needs to be performed to determine the "safe" amount of sunlight exposure for infants and children if we are going to successfully prevent rickets throughout the world.
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DiMaggio, Dina M., et al. "Update in Infant Nutrition." Pediatrics in Review 38.10 October 2017: 449-462.
Mughal, M.Z. "Rickets." Current Osteoporosis Report. 9.4 Dec. 2011: 291-299.