Cystic Fibrosis :: Early onset of poor bone mineralization revealed in children with cystic fibrosis
In a study of children with cystic fibrosis, French researchers found evidence of very early onset defective bone mineration in the lumbar spine that was not caused by either nutritional status or lung disease. The lumbar spine is that part of the back between the ribs and pelvis.
The results of the study, which included children from the age of 2 to puberty, appear in the first issue for May 2007 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
Isabelle Sermet-Gaudelus, M.D., Ph.D., of the Service de P?diatrie G?n?rale, H?pital Necker-Enfants Malades in Paris, and nine associates studied 25 children with cystic fibrosis (CF) younger than six years, 53 prepubertal children with CF aged six to 10, and 36 adolescents 11 to 18 with the disease.
They found that ideal weight for height, fat-free mass and fat mass values decreased significantly as the children aged. Also, pulmonary disease severity increased significantly, mainly in adolescents, as shown by the higher proportion of CF patients colonized with P.auruginosa (gram negative bacteria) and by lower lung function test values.
Among white persons in the U.S., CF is the most common hereditary problem that can lead to death at a relatively early age. The illness causes certain glands to produce abnormal secretions that affect the digestive tract and plug the lungs with mucus. About 1 in every 2,500 white babies is born with this difficulty. The disease is much less common in Blacks and Asians.
The authors believe that their observations of a reduction in bone mineral density, even in healthy children in early childhood, provide an argument for an initial CF defect in primary bone, which can be aggravated by additional disease factors such as low fat-free mass, excessive inflammation, poor nutritional status and low vitamin D levels.
“Deficient bone mineral density is becoming an increasingly important clinical issue in adult patients with CF,” said Dr. Sermet-Gaudelus. “The pathogenesis of low bone mineral density in individuals with CF remains uncertain and bone histomorphometry studies have, thus far, been limited to adults with usually severe CF disease.”
During the test, all of the patient?s values were normalized to compensate for their smaller physical size.
“Bone mineral density is influenced by bone size and can be underestimated in smaller individuals,” said Dr. Sermet-Gaudelus. “Accordingly, the fact that many of the children with CF in our study were smaller than average for their age might have biased our findings. To compensate for differences in body size, bone mineral density was based on height-adjusted rather than chronological age. Lumbar spine bone mineral density scores were thus calculated with reference to a control population of healthy Parisian children and adolescents matched for statural age, sex and puberty status. Our control database included 317 children and adolescents aged 1 to 20 years. . .”
According to the researchers, this is the first study to focus on bone status in patients with CF less than 6 years old, including those as young as 2 years.
“In our study, 60 percent of the normal-weight patients had a low fat-free mass score, a hidden loss that has been previously reported in adults with CF.” said Dr. Sermet-Gaudelus. “Our data demonstrate this can occur in early childhood, even in children with a normal nutritional status. This may be of critical importance in young children and adolescents, because undiagnosed reduction of muscular mass may deprive the growing skeleton of one of its main factors of development.”
(Fat-free mass is the total weight of the body (muscle, bone, skin, and organs) that is not fat. It consists of approximately 73 percent water, 20 percent protein, 6 percent mineral, and 1 percent ash.)
The authors recommend that all children with CF undergo assessment of bone mineral density and body composition early in life in order to target those who need preventive treatment.
“Efforts to obtain and maintain normal bone status in these children must begin early in childhood,” said Dr. Sermet-Gaudelus.