Systemic Inflammation and Normocytic Anemia in DOCK11 Deficiency

BACKGROUND

Increasing evidence links genetic defects affecting actin-regulatory proteins to diseases with severe autoimmunity and autoinflammation, yet the underlying molecular mechanisms are poorly understood. Dedicator of cytokinesis 11 (DOCK11) activates the small Rho guanosine triphosphatase (GTPase) cell division cycle 42 (CDC42), a central regulator of actin cytoskeleton dynamics. The role of DOCK11 in human immune-cell function and disease remains unknown.

METHODS

We conducted genetic, immunologic, and molecular assays in four patients from four unrelated families who presented with infections, early-onset severe immune dysregulation, normocytic anemia of variable severity associated with anisopoikilocytosis, and developmental delay. Functional assays were performed in patient-derived cells, as well as in mouse and zebrafish models.

RESULTS

We identified rare, X-linked germline mutations in DOCK11 in the patients, leading to a loss of protein expression in two patients and impaired CDC42 activation in all four patients. Patient-derived T cells did not form filopodia and showed abnormal migration. In addition, the patient-derived T cells, as well as the T cells from Dock11-knockout mice, showed overt activation and production of proinflammatory cytokines that were associated with an increased degree of nuclear translocation of nuclear factor of activated T cell 1 (NFATc1). Anemia and aberrant erythrocyte morphologic features were recapitulated in a newly generated dock11-knockout zebrafish model, and anemia was amenable to rescue on ectopic expression of constitutively active CDC42.

CONCLUSIONS

Germline hemizygous loss-of-function mutations affecting the actin regulator DOCK11 were shown to cause a previously unknown inborn error of hematopoiesis and immunity characterized by severe immune dysregulation and systemic inflammation, recurrent infections, and anemia. (Funded by the European Research Council and others.).

Dual latent tuberculosis screening with tuberculin skin tests and QuantiFERON-TB assays before TNF-α inhibitor initiation in children in Spain

Tumor-necrosis-factor-α inhibitors (anti-TNF-α) are associated with an increased risk of tuberculosis (TB) disease, primarily due to reactivation of latent TB infection (LTBI). We assessed the performance of parallel LTBI screening with tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube assays (QFT-GIT) before anti-TNF-α treatment in children with immune-mediated inflammatory disorders in a low TB-burden setting. We conducted a multicenter cohort study involving 17 pediatric tertiary centers in Spain. LTBI was defined as the presence of a positive TST and/or QFT-GIT result without clinical or radiological signs of TB disease. A total of 270 patients (median age:11.0 years) were included, mainly with rheumatological (55.9%) or inflammatory bowel disease (34.8%). Twelve patients (4.4%) were diagnosed with TB infection at screening (LTBI, n = 11; TB disease, n = 1). Concordance between TST and QFT-GIT results was moderate (TST+/QFT-GIT+, n = 4; TST-/QFT-GIT+, n = 3; TST+/QFT-GIT-, n = 5; kappa coefficient: 0.48, 95% CI: 0.36-0.60). Indeterminate QFT-GIT results occurred in 10 patients (3.7%) and were associated with young age and elevated C-reactive protein concentrations. Eleven of 12 patients with TB infection uneventfully completed standard LTBI or TB treatment. During a median follow-up period of 6.4 years, only 2 patients developed TB disease (incidence density: 130 (95% CI: 20-440) per 100,000 person-years), both probable de novo infections.

CONCLUSION

A substantial number of patients were diagnosed with LTBI during screening. The dual strategy identified more cases than either of the tests alone, and test agreement was only moderate. Our data show that in children in a low TB prevalence setting, a dual screening strategy with TST and IGRA before anti-TNF-α treatment is effective.

WHAT IS KNOWN

• The optimal screening strategy for latent tuberculosis in children with immune-mediated inflammatory disorders remains uncertain. • Children receiving anti-TNF-α drugs are at increased risk of developing severe tuberculosis disease.

WHAT IS NEW

• A dual screening strategy, using TST and an IGRA assay, identified more children with latent tuberculosis than either of the tests alone. • Identification and treatment of latent tuberculosis before initiation of anti-TNF-α therapy averted incident tuberculosis cases.

Are infections in children with juvenile idiopathic arthritis more frequent than in healthy children? A prospective multicenter observational study

BACKGROUND

Children with juvenile idiopathic arthritis (JIA) might be at a higher risk of infection. Our objectives are to describe and compare infection rates in patients with JIA vs. healthy patients.

METHODS

A prospective, multicenter observational study was performed in Spain from January 2017 to June 2019. Patients with JIA from 7 participating hospitals and children without JIA (siblings of patients with JIA, and non-JIA children from primary health centers) were followed up with quarterly questionnaires to record infection episodes. Tuberculosis, herpes zoster, and infections requiring hospital admission were considered severe infections. Rates of infection (episodes/patient/year) were compared using a generalized estimating equations model.

RESULTS

A total of 371 children (181 with and 190 without JIA) were included. The median age was 8.8 years (IQR 5.5-11.3); 75% of the patients with JIA received immunosuppressive treatment (24% methotrexate, 22% biologic, 26% both). A total of 667 infections were recorded; 15 (2.2%) were considered severe. The infection rate was 1.31 (95%CI 1.1-1.5) in JIA and 1.12 (95%CI 0.9-1.3) in non-JIA participants (p = 0.19). Age <4 years increased the infection rate by 2.5 times (2.72 vs. 1.12, p < 0.001) in both groups. The most frequent infection sites were upper respiratory (62.6% vs. 74.5%) and gastrointestinal (18.8% vs. 11.4%). There were no differences in severe infections (2.5% vs. 2%, p = 0.65) between the groups. In children with JIA, younger age and higher disease activity (JADAS71) were associated with a higher infection rate.

CONCLUSION

We found no differences in the infection rate or infection severity between patients with and without JIA. Most infections were mild. An age younger than 4 years increased the infection risk in both groups. Higher disease activity was associated with a higher infection rate.

Activated PI3Kδ syndrome type 2: Two patients, a novel mutation, and review of the literature

BACKGROUND

Autosomal dominant gain-of-function mutations in PIK3R1 encoding for the regulatory subunit (p85α, p55α, and p50α) of Class IA phosphoinositide 3-kinase (PI3K) result in the activated PI3Kδ syndrome (APDS) type 2 characterized by childhood-onset combined immunodeficiency, lymphoproliferation, and immune dysregulation. To improve clinical awareness and understanding of these rare diseases, we reviewed all hitherto published cases with APDS type 1 and type 2 for their clinical and immunologic symptoms and added novel clinical, immunologic, and genetic findings of two patients with APDS type 2.

METHODS

Clinical, immunologic, and genetic evaluation of two new patients with APDS2 was performed followed by the systematic collection of all available previously published data of patients with APDS1 and APDS2.

RESULTS

Patients with APDS type 1 (n = 49) and type 2 (n = 15) showed an indistinguishable immunologic phenotype. Overlapping clinical features shared by APDS type 1 and type 2 were observed, but our review also revealed previously unnoticed clinical differences such as remarkably high incidence of microcephaly, poor growth/short stature in patients with APDS2. Clinical management and outcome were variable and included prophylactic antibiotics, immunosuppression, immunoglobulin substitution, and hematopoietic stem cell transplantation.

CONCLUSIONS

A disease-specific registry collecting prospective and long-term follow-up data of patients with APDS, as currently set up by the European Society for Immunodeficiencies, are needed to better understand the natural history and to optimize treatment concepts and thereby improving the outcome of this heterogenous patient group.

Infant with probable catastrophic antiphospholipid syndrome successfully managed with rituximab

The antiphospholipid syndrome (APS) is an acquired thrombophilic disorder characterized by the presence of autoantibodies to a variety of phospholipids and phospholipid-binding proteins. Clinical manifestations range from being asymptomatic to having imminently life-threatening events. Catastrophic antiphospholipid syndrome (CAPS) occurs in <1% of patients with APS and is defined by multiple small-vessel occlusions that lead to multiple-organ failure and is associated with high morbidity and mortality rates. Here we report the case of a 3-month-old boy with probable CAPS who presented to us with digital necrosis and pulmonary hemorrhage. In addition, a skin biopsy demonstrated multiple small-vessel thromboses without signs of vasculitis. Results of testing for autoantibodies were positive for anti-beta(2) glycoprotein I (anti-beta(2)-GPI) only. His treatment consisted of high-dose steroids, immunoglobulin therapy, exchange transfusion, cyclophosphamide, and rituximab as well as iloprost and bosentan as vasodilators for his ischemia; he showed an excellent clinical response. To the best of our knowledge, this is the youngest patient with probable CAPS, the first reported patient to test positive for anti-beta(2)-GPI antibodies and negative for anticardiolipin antibodies and lupus anticoagulant, and the second patient reported to be successfully treated with an immunomodulatory regimen including rituximab.