Histiocytosis is a rare disease that involves histiocytes. The disease can range from limited involvement that spontaneously regresses to progressive multiorgan involvement that can be chronic and debilitating. In some cases, the disease can be life-threatening. It is approximated that histiocytosis affects 1 in 200,000 children born each year in the United States. The disease is rare and not much is known securely about how to treat it. Because of its rarity, prospective studies are not possible.Unfortinately the only evidence that is available regarding PET is from case reports. The same is true of treatment ; this is rare disease.
With that caveat, there are a number of reports of PET being useful in this condition. A 2007 report by Kaste et al is representative. It concludes: “We conclude that PET-CT information is clinically useful to evaluate disease activity and response to therapy and provides information that cannot be obtained from technetium 99m methylene diphosphonate bone scans or radiographs.”
We conclude that PET-CT information is clinically useful to evaluate disease activity and response to therapy and provides information that cannot be obtained from technetium 99m methylene diphosphonate bone scans or radiographs.”
PDQ incldues PET in its recommendations. This is what it says in its section on Langerhans:
“Radiologic tests for the first level of screening include skeletal survey, skull series, positron emission tomography (PET), or bone scans, and chest x-ray. Computed tomographic (CT) scan of the head is indicated if orbital or mastoid involvement is suspected. Imaging tests may include magnetic resonance imaging (MRI) scan with gadolinium contrast of the brain for patients with DI or suspected brain or vertebral involvement.A CT scan of the lungs is indicated for patients with abnormal chest x-rays or pulmonary symptoms. High-resolution CT scans may show evidence of pulmonary Langerhans cell histiocytosis (LCH) when the chest x-ray is normal, thus in infants and toddlers with normal chest x-rays, a CT scan may be considered. LCH causes fatty changes in the liver or hypodense areas along the portal tract, which can be identified by CT scans. Newer diagnostic imaging modalities, such as somatostatin analogue scintigraphy or fludeoxyglucose F 18 (18F-FDG) PET scans, which augment these standard methods may prove useful.[4-8] PET scans may be helpful in following the response to therapy since the intensity of the PET image diminishes with healing of a bone or other lesion.
PET-CT in pediatric Langerhans cell histiocytosis.Pediatr Radiol.