Feb. 17, 2012

Reduced Bone Density in Newly Diagnosed Children with Lupus

Low bone mineral density is present in newly diagnosed paediatric systemic lupus erythematosus patients
Lim SH, Benseler SM, Tyrrell PN, Charron M, Harvey E, Hebert D, Silverman ED. (2011). Annals of the Rheumatic Diseases 70: 1991-1994.

What is the topic?

People with lupus are at increased risk of osteoporosis, thinning or loss of bone tissue over time. Children with lupus may be especially susceptible to osteoporosis due to disease mechanisms, steroid treatments, decreased physical activity, vitamin D insufficiency, and/or the timing of their disease. Childhood and adolescence are critical periods of bone growth and, by the end of adolescence, over 90% of bone mass should have been accrued.

What did the researchers hope to learn?

The researchers hoped to learn about the prevalence of low bone mineral density (BMD), as well as to identify risk factors for its development, in a large cohort of newly diagnosed children and adolescents with lupus.

Who was studied?

The study included 80 pediatric lupus (5-18 years old) patients seen at the SickKids Lupus Clinic in Toronto, Canada between December 2001 and 2007.

How was the study conducted?

Each pediatric lupus patient underwent a bone scan within three months of lupus diagnosis. Pediatric lupus patients that also had a history of other diseases known to independently affect bone health were excluded from the study. Each participant received 80 international units/day of vitamin D, as well as 1000 mg/day of calcium supplementation.

Upon entry to the study, demographic information was recorded for each participant, including age, gender, ethnicity, family history of osteoporosis, pubertal status, and menstrual status. At this time, clinical information was also collected for each participant, including neuropsychiatric or kidney involvement, complement and creatinine levels in the blood, lupus disease activity, and drug treatments.

At the time of bone scans, height and weight were recorded for each participant, and body mass index (BMI) was calculated accordingly. Bone mineral density measurements were classified as being either “low,” “low-normal,” or “abnormal.”

For each participant, bone density was scanned at three different sites on the lower spine. In addition, two bone density scans were performed on the hip (one scan for each side). In addition, for each participant, markers of bone function were assessed, including blood levels of 25-hydroxyvitamin D (the biologically active form of vitamin D) and calcium (important for vitamin D absorption).

Advanced statistics were used to determine the relationship between bone scan measurements and the aforementioned clinical or laboratory measures, as well as to determine the impact of steroid use on bone density in children with lupus.

What did the researchers find?

The study participants were mostly Caucasian and Asian pubertal girls who were an average age of 14 year old at the time of lupus diagnosis. Few of the participants had a family history of osteoporosis, or had brain or kidney involvement.

Forty-six percent of patients underwent bone scanning within the first month of lupus diagnosis, while 20% were scanned between the first and second months after diagnosis. Twenty-eight percent of patients had not been treated with steroids at the time of bone scanning. At the time of bone scans, 34% were taking hydroxychloroquine and 24% were taking an immune-suppressing drug (mostly azathioprine).

In terms of bone density, 15% of patients were classified as “low” and 33% were classified as “abnormal.” There were no significant differences in bone density at either the spine or hip between participants who had been exposed to steroids and those who had not. Patients who had been exposed to steroids were not at increased risk of having lower bone density in either the spine or hip. Furthermore, reduced bone density was not significantly associated with overall lupus disease activity or lupus treatments (including steroids and other treatments).

Reduced bone density measurements were significantly associated with lower BMI (at the time of lupus diagnosis), as well as with reduced calcium levels in the blood. Reduced hip bone density measurements were significantly associated with lower BMI (at the time of lupus diagnosis).

What were the limitations of the study?

Data regarding genetics and levels of physical activity for patients may have been useful but were not available. In addition, the patients included in the study tended to have higher lupus disease activity than those excluded.

What do the results means for you?

Steroid exposure within the first three months of lupus diagnosis does not appear to significantly increase risk of reduced bone density. The authors recommend that all newly diagnosed pediatric lupus patients undergo a bone scan, especially those having some of the risk factors identified in this study. It is also important to encourage adequate calcium and vitamin D intake in all people with lupus, particularly because sunscreen use is advised in all lupus patients, which may lead to vitamin D deficiency. Long-term follow-up of these patients will be required to further understand their future bone-related health outcomes.

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