NEW ORLEANS — Nutritional rickets caused by vitamin D deficiency persists, in part because the risk factors may not be fully appreciated, Dr. Arlette Soros and colleagues reported in a poster at the Southern regional meeting of the American Federation for Medical Research.
The authors have encountered nearly a dozen cases in the last decade at Children's Hospital in New Orleans, and have documented four representative cases. The children, aged 3 months to 3 years, shared similar risk factors of limited sun exposure, darker skin pigmentation, and having been breast-fed without any vitamin D supplementation.
Breast milk typically contains a vitamin D concentration of 25 IU or less per liter, which falls far short of the daily recommended minimum intake of 200 IU per day for infants, said Dr. Soros, a pediatrician with the division of endocrinology at Louisiana State University, New Orleans.
“It's wrong to think that a baby will get all the nutrients it needs from breast milk, and not give vitamin D supplementation” she said in an interview. “They may appear healthy, but there is a deficiency going on.”
In addition, synthesis of vitamin D from ultraviolet sunlight is decreased in darker skin pigmentation. Lifestyle and cultural factors may further limit sunlight exposure.
Three of the children were African American and one was Arabic. They presented with tetany, bony deformities such as bowed legs, widening of wrists and ankles, and rachitic rosary.
All of the children had low serum total calcium (range 6.1–7.8 mg/dL) and ionized calcium levels (range 2.2- 4.3 mg/dL); relatively low normal serum phosphorus levels (range 4.3–6.1 mg/dL), and elevated alkaline phosphatase levels (range 391–1,158 U/L).
All had low serum 25-hydroxy vitamin D (range 5.0–21 ng/mL), high parathyroid hormone levels (range 143–454 pg/mL), and relatively high 1,25-dihydroxy vitamin D levels (range 93–195 pg/mL). Renal and liver functions were normal.
One boy had even been put in a soft cast because his pediatrician misdiagnosed the rickets as a sprain. After a single dose of intravenous calcium, ergocalciferol, or calcitriol, all of the children had complete or near-complete resolution of their symptoms. “He was up running the next day,” Dr. Soros said. “This is very preventable.”
In 2003, the American Academy of Pediatrics published new guidelines for vitamin D intake and recommended supplementation of 200 IU for all breast-fed infants. It also has issued directives that infants younger than 6 months should be kept out of direct sunlight.
For the most part, the problem of nutritional rickets has been well identified, although pediatricians are responsible for tolerating lower levels of vitamin D, particularly in African American, Arabic, and Hispanic children, senior author Dr. Alfonso Vargas, professor of pediatrics at Louisiana State, said in an interview.
“The message from the AAP is not collating quickly enough,” he said. “The beauty of this study shows that if a child's vitamin D needs are not addressed, they will be in serious trouble quite quickly.”
The fraying and lack of calcification seen in this x-ray are typical of rickets. Courtesy Dr. Alfonso Vargas/Children's Hospital