Immunosuppression, IBD, and risk of lymphoma

Diagnostic medical radiation in inflammatory bowel disease: how to limit risk and maximize benefit

Diagnosis and management of inflammatory bowel disease (IBD) requires repeat diagnostic imaging for monitoring of disease activity. Recent evidence has suggested that patients with IBD are at increased risk of radiation exposure from repeat imaging. The aim of this article was to highlight risks associated with increasing radiation exposure and identify alternatives to minimize exposure. The increasing use of computed tomography (CT) in both Crohn's disease and ulcerative colitis has brought additional benefits to guiding management through non-invasive measures. However, the massive increase in use of CT scans poses a risk of exposing patients with IBD to high levels of diagnostic medical radiation. High levels of diagnostic medical radiation are associated with an increased risk of malignancy in several studies. Numerous studies have identified particular risk factors in IBD associated with high levels of diagnostic medical radiation which are also associated with a more severe disease course. Imaging techniques such as magnetic resonance enterography, ultrasound, small bowel follow through, and capsule endoscopy are alternatives to CT scans as they do not utilize radiation. Gastroenterologists managing patients with IBD, particularly Crohn's disease, should be aware of the increased risk of high cumulative doses of radiation exposure, particularly from CT scanning. Alternative forms of imaging should be carefully considered when evaluating patients, in particularly those with identifiable risk factors for an aggressive disease course.

Long-term outcome of intractable ulcerating enterocolitis of infancy

BACKGROUND

Chronic enterocolitis is rare in infancy and accounts for less than 0.5% of all newly diagnosed inflammatory bowel disease (IBD) in the UK. Presentation at this young age is usually indicative of underlying immunodeficiency/immunodysregulation. A group of such infants suffer intractable ulcerating enterocolitis of infancy (IE) in which there is a pan-enteritis with marked oro-anal involvement and deep flask like mucosal ulcers throughout the colon.

METHODS

Retrospective review of presenting features, treatment and long-term outcome in a series of 8 children with typical IE.

RESULTS

The 8 children were aged between 1 and 4 weeks at onset (median 2 weeks, mean 2.3 weeks), of which 7 were followed up for 2-22 years (median 7.5 years, mean 11 years). All 8 children had an intractable disease course requiring a colectomy for control of symptoms. The median age at colectomy was 1.7 years (range 4 months-4 years). Three children developed a generalised lymphadenopathy due to uncontrolled EBV-related lymphoid proliferations (ages 4, 12, 18). These comprised a monomorphous B-lymphoycte lympho-proliferative disorder, a large pleomorphic follicular lymphoma, and a high grade pleomorphic B cell non-Hodgkin's lymphoma.

CONCLUSIONS

Infants with IE have a high risk of developing lymphomatous proliferations that appears to be related to the underlying immunodysregulation. Use of aggressive immunosuppression and acquisition of EBV infection appears to accelerate this process; hence we advocate early colectomy in confirmed cases. In children with IE screening for EBV and vigilance for abnormal lymphoid proliferations is paramount.

Nonlinear dose-response relationship in the immune system following exposure to ionizing radiation: mechanisms and implications

The health effects of low-dose radiation (LDR) have been the concern of the academic spheres, regulatory bodies, governments, and the public. Among these effects, the most important is carcinogenesis. In view of the importance of immune surveillance in cancer control, the dose-response relationship of the changes in different cell types of the immune system after whole-body irradiation is analyzed on the basis of systemic data from the author's laboratory in combination with recent reports in the literature. For T lymphocytes J- or inverted J-shaped curves are usually demonstrated after irradiation, while for macrophages dose-response curves of chiefly stimulation with irregular patterns are often observed. The intercellular reactions between the antigen presenting cell (APC) and T lymphocyte (TLC) in the immunologic synapse via expression of surface molecules and secretion of cytokines by the two cell types after different doses of radiation are illustrated. The different pathways of signal transduction thus facilitated in the T lymphocyte by different doses of radiation are analyzed to explain the mechanism of the phenomenon of low-dose stimulation and high-dose suppression of immunity. Experimental and clinical data are cited to show that LDR retards tumor growth, reduces metastasis, increases the efficacy of conventional radiotherapy and chemotherapy as well as alleviates the suppression of immunity due to tumor burden. The incidence of thymic lymphoma after high-dose radiation is lowered by preexposure to low-dose radiation, and its mechanism is supposed to be related to the stimulation of anticancer immunity induced by low-dose radiation. Recent reports on lowering of standardized cancer mortality rate and all cause death rate of cohorts occupationally exposed to low-dose radiation from the US, UK, and Canada are cited.