Cystic lung lesions as an immune reconstitution inflammatory syndrome (IRIS) in HIV-TB co-infection?

Pulmonary manifestations of the immune reconstitution inflammatory syndrome

PURPOSE OF REVIEW

Immune reconstitution inflammatory syndrome (IRIS) is a common occurrence in HIV patients starting antiretroviral therapy (ART), and pulmonary involvement is an important feature of tuberculosis-IRIS and pneumocystis-IRIS. Pulmonologists need an awareness of the timing, presentation and treatment of pulmonary IRIS.

RECENT FINDINGS

Case definitions for tuberculosis-IRIS and cryptococcal-IRIS have been published by the International Network for the Study of HIV-associated IRIS (INSHI). A number of studies have addressed validation of clinical case definitions and the optimal time to commence ART after diagnosis of an opportunistic infection in HIV patients. The pathogenesis of IRIS is being assessed at a molecular level, increasing our understanding of mechanisms and possible targets for future preventive and therapeutic strategies.

SUMMARY

Tuberculosis-IRIS, nontuberculosis mycobacterial-IRIS and pneumocystis-IRIS occur within days to weeks of starting ART, causing substantial morbidity, but low mortality. Cryptococcal-IRIS usually occurs later in the course of ART, and may be associated with appreciable mortality. Early recognition of unmasking and paradoxical IRIS affecting the lung allows timely initiation of antimicrobial and/or immunomodulatory therapies.

Tuberculosis-associated immune reconstitution inflammatory syndrome and unmasking of tuberculosis by antiretroviral therapy

The tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is a frequent early complication of antiretroviral therapy (ART), used to treat HIV-1 infection, especially in countries where TB is prevalent. TB-IRIS is characterized by an exaggerated inflammatory response toward the antigens of Mycobacterium tuberculosis that results in clinical deterioration in patients experiencing immune recovery during early ART. Two forms of TB-IRIS are recognized: paradoxical; and unmasking. Paradoxical TB-IRIS manifests with new or recurrent TB symptoms or signs in patients being treated for TB during early ART, and unmasking TB-IRIS is characterized by an exaggerated, unusually inflammatory initial presentation of TB during early ART. In this review the incidence, clinical features, risk factors, treatment, and prevention of TB-IRIS in adult and pediatric patients are discussed.

Immune restoration diseases reflect diverse immunopathological mechanisms

Up to one in four patients infected with human immunodeficiency virus type 1 and given antiretroviral therapy (ART) experiences inflammatory or cellular proliferative disease associated with a preexisting opportunistic infection, which may be subclinical. These immune restoration diseases (IRD) appear to result from the restoration of immunocompetence. IRD associated with intracellular pathogens are characterized by cellular immune responses and/or granulomatous inflammation. Mycobacterial and cryptococcal IRD are attributed to a pathological overproduction of Th1 cytokines. Clinicopathological characteristics of IRD associated with viral infections suggest different pathogenic mechanisms. For example, IRD associated with varicella-zoster virus or JC polyomavirus infection correlate with a CD8 T-cell response in the central nervous system. Exacerbations or de novo presentations of hepatitis associated with hepatitis C virus (HCV) infection following ART may also reflect restoration of pathogen-specific immune responses as titers of HCV-reactive antibodies rise in parallel with liver enzymes and plasma markers of T-cell activation. Correlations between immunological parameters assessed in longitudinal sample sets and clinical presentations are required to illuminate the diverse immunological scenarios described collectively as IRD. Here we present salient clinical features and review progress toward understanding their pathogeneses.

The radiology of IRIS (immune reconstitution inflammatory syndrome) in patients with mycobacterial tuberculosis and HIV co-infection: appearances in 11 patients

AIM

To determine the radiological manifestations of IRIS (immune reconstitution inflammatory syndrome) in patients with HIV and mycobacterium tuberculosis co-infection, in the context of their demographic and clinical data.

MATERIALS AND METHODS

The radiological imaging, demographic and clinical data of 11 patients diagnosed with IRIS associated with HIV and mycobacterial tuberculosis co-infection were studied retrospectively. Where available, follow-up imaging studies were also reviewed.

RESULTS

The most common radiological feature of IRIS was lymph node enlargement (73%), with central low attenuation centres, in keeping with necrosis, present in most of these cases (88%). Most commonly affected were intra-abdominal nodes (70%), followed by axillary (40%) and mediastinal lymph nodes (36%). Within the lung parenchyma, diffuse, bilateral pulmonary nodules were seen in 55% of cases. Unilateral small volume pleural effusions were seen in two cases with associated parenchymal changes seen in only one. Small volume ascites was seen in two cases. Thirty-six percent of cases presented with new or worsening abscesses despite treatment. In this context, image-guided radiological drainage proved a useful adjunct to the conventional medical therapy for IRIS. The most common clinical signs of IRIS included fever (64%), abdominal pain (36%) and cough (27%).

CONCLUSION

We have described the radiological features that are characteristic in IRIS and the importance of putting these into context with the clinical and pathological findings as part of a multidisciplinary approach in making the diagnosis. The role of the radiologist is central in diagnosis, monitoring of disease progression and management of complications in patients with IRIS.

Immune reconstitution inflammatory syndrome in HIV

PURPOSE OF REVIEW

The purpose of this review is to describe the epidemiology, clinical features, putative immune mechanisms and management of immune reconstitution inflammatory syndrome (IRIS) using data published in the last 2 years.

RECENT FINDINGS

Ever more conditions are reported as IRIS events. These most frequently occur with mycobacterial (tuberculosis or Mycobacterium avium complex infection) or cryptococcal disease (each in approximately 30% of cases). Definitions have been proposed for its clinical diagnosis. These suffer from a lack of prospective studies to support their predictive value. The immunopathogenesis of IRIS appears to be related to the interaction between HAART-induced changes in host immune response and the presence of (usually microbial) antigen. Increasing evidence exists that this might be an anatomically compartmentalized phenomenon, such that immune responses may be localized to specific tissue sites such as the brain. This has implications for the use of simple blood tests, such as CD4 count or change in viral load, when assessing risk of IRIS. Treatment options include immune modulation, though supportive care is typically all that is required, unless symptoms are prolonged, significant or life-threatening.

SUMMARY

IRIS is common and will become more so as HAART is rolled out worldwide. Clear clinical definitions are required to avoid its over-diagnosis due to misclassification of other conditions.