Investigators at the National Institutes of Health have demonstrated that a disabling bone disorder, osteonecrosis of the hip, is surprisingly common among patients with HIV infection.
The study results will be presented during the Infectious Diseases Society of America's annual meeting Sept. 8 in New Orleans.
Concern that the disorder might be a new and unrecognized complication of HIV infection prompted the investigation, a collaboration between the NIH Clinical Center and the National Institute of Allergy and Infectious Diseases (NIAID).
Magnetic resonance imaging was used to evaluate 339 study volunteers, all patients with HIV. While none of the study participants had the hip pain typically associated with osteonecrosis, 15 (4.4 per cent) were found to have the disorder. As a comparison, 118 patients without HIV were tested, and none were found to have osteonecrosis.
"These 15 patients with asymptomatic osteonecrosis had lesions in one or both hips," noted Dr. Henry Masur, critical care medicine chief at the NIH Clinical Center. "Many of the lesions were large. Our concern is that the lesions will lead to clinical symptoms ultimately requiring total hip replacements."
The reason for this unexpected complication of osteonecrosis-bone death-is unclear. "We've been following patients with HIV at the NIH Clinical Center for more than 17 years and had not seen this complication until about a year ago," said Dr. Joseph Kovacs, also of the NIH hospital's Critical Care Medicine Department. "Longer patient survival, new therapies, or lifestyle influences may somehow contribute to the development of this disorder. It's important to find out why it's happening."
While researchers can't yet pinpoint a specific cause, patients in this study found to have osteonecrosis were more likely to have taken testosterone, lipid-lowering drugs, and corticosteroids, all prescribed therapies for the acute and chronic complications of HIV infection or other common medical problems. They were also more likely to have been involved in weight-training and body-building. The occurrence of osteonecrosis was not associated with the level of immunodeficiency or any particular pattern of antiretroviral use.
"In 1999, four of our patients with HIV developed hip and groin pain that was subsequently diagnosed as osteonecrosis, also known as avascular necrosis," added Dr. Masur. "In evaluating these cases, we learned that other physicians around the country were seeing a small but increasing number of HIV-infected patients with osteonecrosis. To prevent the development of osteonecrosis, it was clearly important to find out how many of our asymptomatic patients were developing these lesions and pinpoint contributing factors."
"Researchers from both NIH Clinical Center and NIAID conduct numerous research studies at the NIH hospital in Bethesda currently involving about 600 volunteer patients with HIV infection," noted Dr. John I. Gallin, NIH Clinical Center director. "Participants in this study were drawn from this cohort of patients. A critical mass of patient volunteers enables research at the NIH Clinical Center to track how diseases such as HIV evolve."
A longitudinal study is under way to determine how many patients will develop these lesions and how many will ultimately need hip replacement. Larger studies are needed to identify factors that contribute to the development of osteonecrosis, Dr. Kovacs said. "If we can identify what's causing the disorder among these patients, we are hopeful we can determine a way to prevent and treat it."