La granulomatose septique chronique

NADPH Oxidases (NOX): An Overview from Discovery, Molecular Mechanisms to Physiology and Pathology

The reactive oxygen species (ROS)-producing enzyme NADPH oxidase (NOX) was first identified in the membrane of phagocytic cells. For many years, its only known role was in immune defense, where its ROS production leads to the destruction of pathogens by the immune cells. NOX from phagocytes catalyzes, via one-electron trans-membrane transfer to molecular oxygen, the production of the superoxide anion. Over the years, six human homologs of the catalytic subunit of the phagocyte NADPH oxidase were found: NOX1, NOX3, NOX4, NOX5, DUOX1, and DUOX2. Together with the NOX2/gp91phox component present in the phagocyte NADPH oxidase assembly itself, the homologs are now referred to as the NOX family of NADPH oxidases. NOX are complex multidomain proteins with varying requirements for assembly with combinations of other proteins for activity. The recent structural insights acquired on both prokaryotic and eukaryotic NOX open new perspectives for the understanding of the molecular mechanisms inherent to NOX regulation and ROS production (superoxide or hydrogen peroxide). This new structural information will certainly inform new investigations of human disease. As specialized ROS producers, NOX enzymes participate in numerous crucial physiological processes, including host defense, the post-translational processing of proteins, cellular signaling, regulation of gene expression, and cell differentiation. These diversities of physiological context will be discussed in this review. We also discuss NOX misregulation, which can contribute to a wide range of severe pathologies, such as atherosclerosis, hypertension, diabetic nephropathy, lung fibrosis, cancer, or neurodegenerative diseases, giving this family of membrane proteins a strong therapeutic interest.

[Auto-immune hepatitis in chronic granulomatous disease in a 2-year-old girl]

BACKGROUND

Chronic granulomatous disease is a rare inherited primary immune deficiency disease characterized by recurrent infection and an increased susceptibility to autoimmunity disorders. We report on the case of a girl with autoimmune hepatitis in chronic granulomatous disease to describe the clinical and biological features and treatment implications for patients with chronic granulomatous disease associated with autoimmune disorders.

CASE REPORT

An 18-month-old girl was referred to our department for investigation of hepatomegaly. She was the third child of non-consanguineous parents. Her two elder sisters had died from infectious diseases at an early age. She had elevated liver transaminase levels with a normal gamma globulin concentration. Negative results were found for all autoimmune markers (antinuclear antibody, anti-smooth muscle, anti-liver-kidney microsomal, anti-liver cytosol and anti-soluble liver antigen). Her liver biopsy showed features of interface hepatitis with portal fibrosis. The diagnosis of seronegative autoimmune hepatitis was established. Treatment with corticosteroids and azathioprine led to clinical improvement with normalization of transaminases. Six months after initial presentation, at the age of 2 years, she was readmitted for fever. Staphylococcus aureus bacteremia was identified with multiple foci of infection (skin infection, arthritis of the right elbow, pneumonia, buttock abscess). The immunological workup revealed chronic granulomatous disease. The course was marked by a fatal outcome despite appropriate antibiotics and intensive care.

CONCLUSION

Early diagnosis of the association between chronic granulomatous disease and autoimmune disorders allows for appropriate treatments, improves the quality of life for affected patients, and reduces the risk of mortality.

Pulmonary manifestations in adult patients with chronic granulomatous disease

Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by failure of superoxide production in phagocytic cells. The disease is characterised by recurrent infections and inflammatory events, frequently affecting the lungs. Improvement of life expectancy now allows most patients to reach adulthood. We aimed to describe the pattern of pulmonary manifestations occurring during adulthood in CGD patients. This was a retrospective study of the French national cohort of adult patients (≥16 years old) with CGD. Medical data were obtained for 67 adult patients. Pulmonary manifestations affected two-thirds of adult patients. Their incidence was significantly higher than in childhood (mean annual rate 0.22 versus 0.07, p=0.01). Infectious risk persisted despite anti-infectious prophylaxis. Invasive fungal infections were frequent (0.11 per year per patient) and asymptomatic in 37% of the cases. They often required lung biopsy for diagnosis (10 out of 30). Noninfectious respiratory events concerned 28% of adult patients, frequently associated with a concomitant fungal infection (40%). They were more frequent in patients with the X-linked form of CGD. Immune-modulator therapies were required in most cases (70%). Respiratory manifestations are major complications of CGD in adulthood. Noninfectious pulmonary manifestations are as deleterious as infectious pneumonia. A specific respiratory monitoring is necessary.

[Ocular manifestations in chronic granulomatous disease]

Chronic granulomatous disease (CGD) is a rare genetic immune deficiency due to defective oxygen metabolism in phagocytic cells. It results in recurrent severe bacterial and fungal infections in patients from an early age on. Inflammatory lesions are also observed, with the formation of granulomas. Diagnosis relies on the demonstration of a deficiency in the oxidative properties of phagocytes. Pulmonary infections are the most frequent clinical manifestations of the disease, yet all organs can be involved, such as the eye, with either infections or inflammatory chorioretinal lesions. The treatment of CGD relies on prophylaxis to avoid infections, and on the rapid management of infectious and inflammatory episodes. The only cure to date is allogenetic bone marrow transplant, which requires a compatible donor and can only be considered in certain clinical situations.

[Lymphohistiocytic activation syndrome and Burkholderia cepacia complex infection in a child revealing chronic granulomatous disease and chromosomal integration of the HHV-6 genome]

Chronic granulomatous disease (GCD) is characterized by severe infections, notably with Burkholderia cepacia complex (BCC). GCD is rarely complicated by lymphohistiocytic activation syndromes, most often secondary to bacterial or viral infections, in particular human herpes virus 6 (HHV-6). We describe the case of a 10-month-old boy who suffered from multiple organ failure due to a BCC infection and a lymphohistiocytic activation syndrome, leading to diagnosis of GCD. The initial search for HHV-6 was positive and the infection was treated, but the progression and viral sample analysis led to the chromosomal integration of the HHV-6 genome. The child's clinical condition was normal after bone marrow transplantation. This case describes a rare association between GCD and lymphohistiocytic activation syndrome and raises questions about the role played by chromosomal integration of the HHV-6 genome.

Interstitial lung diseases in children

Interstitial lung disease (ILD) in infants and children comprises a large spectrum of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. These disorders are characterized by inflammatory and fibrotic changes that affect alveolar walls. Typical features of ILD include dyspnea, diffuse infiltrates on chest radiographs, and abnormal pulmonary function tests with restrictive ventilatory defect and/or impaired gas exchange. Many pathological situations can impair gas exchange and, therefore, may contribute to progressive lung damage and ILD. Consequently, diagnosis approach needs to be structured with a clinical evaluation requiring a careful history paying attention to exposures and systemic diseases. Several classifications for ILD have been proposed but none is entirely satisfactory especially in children. The present article reviews current concepts of pathophysiological mechanisms, etiology and diagnostic approaches, as well as therapeutic strategies. The following diagnostic grouping is used to discuss the various causes of pediatric ILD: 1) exposure-related ILD; 2) systemic disease-associated ILD; 3) alveolar structure disorder-associated ILD; and 4) ILD specific to infancy. Therapeutic options include mainly anti-inflammatory, immunosuppressive, and/or anti-fibrotic drugs. The outcome is highly variable with a mortality rate around 15%. An overall favorable response to corticosteroid therapy is observed in around 50% of cases, often associated with sequelae such as limited exercise tolerance or the need for long-term oxygen therapy.

Dual oxidases and hydrogen peroxide in a complex dialogue between host mucosae and bacteria

Among the host defense mechanisms against bacteria, leukocyte phagocytosis leads to their hydrogen peroxide (H(2)O(2))-mediated destruction. The recent discovery of dual oxidase (DUOX)-dependent H(2)O(2) generation associated with peroxidase and thiocyanate secretion at the apex of mucosal cells has been similarly interpreted as a killing mechanism. However, the rapid degradation of H(2)O(2) would be expected to reduce the efficiency of this system. It has been demonstrated that H(2)O(2) acts as a chemorepellent for bacteria, and such an effect might be sufficient to block cellular infection. Therefore, H(2)O(2) generation might represent one of the mechanisms that allows the coexistence of mucosae with potentially harmful bacteria. Here, we discuss the possible role of DUOXes and H(2)O(2) in interactions between host mucosae and bacteria to maintain mucosal homeostasis.