Pediatric recurrent respiratory papillomatosis (RRP) can be devastating for patients and their families. The disease is caused by two strains of the human papilloma virus, HPV-6 and HPV-11, and affects approximately 4 in 100,000 children. The disease course is highly variable, with some children requiring only one or two surgeries and others requiring a hundred. Research and new tools are helping to improve patient care, though many questions remain unanswered and the rarity of the disease makes finding some answers difficult.
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October 2006HPV Type Influences Disease Course
Several recent studies show that HPV-11 is more frequently associated with aggressive RRP than is HPV-6, though both strains are associated with genital warts or condylomas in adults. In a 10-year prospective study of 73 pediatric RRP patients, Brian J. Wiatrak, MD, Chief of Pediatric Otolaryngology at The Children’s Hospital of Alabama in Birmingham, and colleagues found that patients infected with HPV-11 had a higher severity score at presentation, required more frequent surgeries, and more frequently required medical adjuvant therapies to control disease compared with patients infected with HPV-6.
HPV-16, which is known to cause cervical cancer in women, is infrequently found to infect the airway. When it does however, the likelihood that RRP will progress to cancer increases, said Dr. Wiatrak, and patients should be followed more closely.
Given these differences in disease course, Dr. Wiatrak regularly tests new patients to determine which HPV type they are infected with. If it is HPV-11, you know ahead of time that you are going to be dealing with a more aggressive subtype and you can adjust your clinical plan accordingly, he said. When treating such patients he is likely to electively schedule more frequent debridements to stay ahead of the disease as it can get out of control rather quickly. Additionally, he is more likely to start adjuvant medical treatments with this type of infection.
One problem with typing, however, is that the currently available commercial tests do not distinguish between HPV-6 and -11. Rather, the results come back in the form of low risk or high risk with respect to cancer, not RRP. As both HPV-11 and HPV-6 fall in the low-risk category for cancer, the tests are not particularly useful for RRP prognosis. Roche Laboratories plans to come out with a more specific test in the next few years, which will discriminate between -11 and -6, but until then such tests are really available only in research facilities. So general clinicians cannot find out what specific type they are dealing with unless they have a research lab they are associated with-and then only the commercially available tests are covered by insurance, said Dr. Wiatrak.
Host Factors Influence Susceptibility
In addition to viral subtype, host variables play a big role in who gets the disease and how it manifests itself. A key indication that host factors are important is the low rate of disease relative to the number of children exposed to the virus. Only seven of 1000 children born to women with condylomas develop RRP, although mother-to-child transmission during fetal development or delivery is the major route of infection.