The challenge of early diagnosis of autoimmune lymphoproliferative syndrome in children with suspected autoinflammatory/autoimmune disorders

Nonspecific increase of αβTCR+ double-negative T cells in pediatric rheumatic diseases

BACKGROUND

An increased number of double-negative T (DNT) cells expressing the αβ T cell receptor (αβ+DNT cells) is one of the diagnostic criteria for autoimmune lymphoproliferative syndrome (ALPS). Moreover, these cells are expanded in a widely used murine model for lupus. However, the homeostasis of αβ+DNT cells remains inadequately investigated in rheumatic disorders, especially in pediatric patients.

METHODS

In this cross-sectional, prospective, and observational study, children with rheumatic disorders and healthy controls were recruited to analyze the quantity and characteristics of circulating DNT cells using flow cytometry.

RESULTS

Overall, the two study groups did not differ in their total DNT cell pool in the bloodstream. However, the number of αβ+DNT cells was significantly higher in rheumatic children than that in the controls, whereas the γδ+DNT cells remained similar. This expansion in the circulating pool of αβ+DNT cells was comparable across different rheumatic diseases, all showing significant differences from the controls in this regard. Moreover, no significant correlation was found between αβ+DNT cell numbers and disease activity.

CONCLUSIONS

These preliminary results indicate that circulating αβ+DNT cells are significantly expanded in children with rheumatic disorders; however, this finding appears to be a nonspecific (disease-unrelated) marker of autoimmunity. Further and larger studies are necessary to better investigate and define the role of DNT cells in pediatric rheumatic diseases.

Double-negative T cells in pediatric rheumatic diseases

Double-negative (CD4-CD8-) T (DNT) cells have been implicated in autoimmune lymphoproliferative syndrome (ALPS), where their expansion inside the circulating pool of T cells represents a diagnostic criterion. Recent experimental evidence has supported the immunomodulatory roles of DNT cells, and studies in adult patients have suggested that they may be altered in some immune-mediated conditions. This study aimed to retrieve available data on circulating DNT cells in pediatric rheumatic disorders that do not arise in the context of ALPS through a systematic literature review of 3 scientific databases (PubMed, Scopus, and Web of Science). The final output of the systematic literature search consisted of 8 manuscripts, including cross-sectional (n=6) and longitudinal (n=2) studies. Overall, the pooled population of patients includes children affected with pediatric systemic lupus erythematosus (n= 104), juvenile idiopathic arthritis (n=92), Behçet's disease (n=15), mixed connective tissue disease (n=8), juvenile dermatomyositis (n=6), and Kawasaki disease/multisystem inflammatory disease in children (n=1 and n=14, respectively); moreover, one study also included 11 children with a high titer of antinuclear antibody but no diagnosis of rheumatic disease. All studies except one included a control group. The number of DNT cells were increased in most studies of children with rheumatic diseases. Even if such a limited number of studies and their great heterogeneity in several methodological aspects do not allow for reliable conclusions about the relevance of DNT cells in specific rheumatic conditions in children, this cell population deserves further investigation in this pathological setting through well-designed clinical studies.

Revisiting double-negative T cells in autoimmune lymphoproliferative immunodeficiencies: a case series

BACKGROUND

Elevated level of double-negative T (DNT) cells is a historical hallmark of autoimmune lymphoproliferative syndrome (ALPS) diagnosis. However, the peripheral blood level of DNT cells might also be compromised in autoimmune lymphoproliferative immunodeficiencies (ALPID) other than ALPS, inattention to which would increase the delay in diagnosis of the underlying genetic defect and hinder disease-specific treatment.

MATERIALS AND METHODS

This cross-sectional study recruited patients suffering from ALPID (exclusion of ALPS) with established genetic diagnosis. Following thorough history taking, immunophenotyping for lymphocyte subsets was performed using BD FACS CaliburTM flowcytometry.

RESULTS

Fifteen non-ALPS ALPID patients (60% male and 40% female) at a median (interquartile range: IQR) age of 14.0 (7.6-21.8) years were enrolled. Parental consanguinity and family history of immunodeficiency were present in 8 (53.3%) patients. The median (IQR) age at first presentation, clinical and molecular diagnosis were 18 (4-36) months, 8.0 (4.0-17.0) years, and 9.5 (5.0-20.9) years, respectively. Molecular defects were observed in these genes: LRBA (3, 20%), CTLA-4 (2, 13.3%), BACH2 (2, 13.3%), AIRE (2, 13.3%), and FOXP3, IL2Rβ, DEF6, RASGRP1, PIK3CD, and PIK3R1 each in one patient (6.7%). The most common manifestations were infections (14, 93.3%), autoimmunity (12, 80%), and lymphoproliferation (10, 66.7%). The median (IQR) count of white blood cells (WBCs) and lymphocytes were 7160 (3690-12,600) and 3266 (2257-5370) cells/mm3, respectively. The median (IQR) absolute counts of CD3+ T lymphocytes and DNTs were 2085 (1487-4222) and 18 (11-36) cells/mm3, respectively. Low lymphocytes and low CD3+ T cells were observed in 3 (20%) patients compared to normal age ranges. Only one patient with FOXP3 mutation had DNT cells higher than the normal range for age.

CONCLUSIONS

Most non-ALPS ALPID patients manifested normal DNT cell count. For a small subgroup of patients with high DNT cells, defects in other IEI genes may explain the phenotype and should be included in the diagnostic genetic panel.

Probable Autoimmune Lymphoproliferative Syndrome with Monogenic Lupus Due to KRAS Mutation

Autoimmune lymphoproliferative syndrome (ALPS) is a disease characterized by dysfunction of the T lymphocyte  apoptotic pathways, mostly due to dysfunctional FAS mediated signaling. However few cases can also occur independent of FAS pathway alteration. ALPS is characterized by various immuno-hematological manifestations. Monogenic lupus is an evolving entity, which describes the etiologic role of single gene modulation in systemic lupus erythematosus. In this manuscript, we describe a case of probable ALPS with monogenic lupus caused by a novel mutation in the KRAS gene.

Underlying Inborn Errors of Immunity in Patients With Evans Syndrome and Multilineage Cytopenias: A Single-Centre Analysis

Background

Evans syndrome (ES) is a rare disorder classically defined as the simultaneous or sequential presence of autoimmune haemolytic anaemia and immune thrombocytopenia, but it has also been described as the presence of at least two autoimmune cytopenias. Recent reports have shown that ES is often a manifestation of an underlying inborn error of immunity (IEI) that can benefit from specific treatments.

Aims

The aim of this study is to investigate the clinical and immunological characteristics and the underlying genetic background of a single-centre cohort of patients with ES.

Methods

Data were obtained from a retrospective chart review of patients with a diagnosis of ES followed in our centre. Genetic studies were performed with NGS analysis of 315 genes related to both haematological and immunological disorders, in particular IEI.

Results

Between 1985 and 2020, 40 patients (23 men, 17 women) with a median age at onset of 6 years (range 0-16) were studied. ES was concomitant and sequential in 18 (45%) and 22 (55%) patients, respectively. Nine of the 40 (8%) patients had a positive family history of autoimmunity. Other abnormal immunological features and signs of lymphoproliferation were present in 24/40 (60%) and 27/40 (67%) of cases, respectively. Seventeen out of 40 (42%) children fit the ALPS diagnostic criteria. The remaining 21 (42%) and 2 (5%) were classified as having an ALPS-like and an idiopathic disease, respectively. Eighteen patients (45%) were found to have an underlying genetic defect on genes FAS, CASP10, TNFSF13B, LRBA, CTLA4, STAT3, IKBGK, CARD11, ADA2, and LIG4. No significant differences were noted between patients with or without variant and between subjects with classical ES and the ones with other forms of multilineage cytopenias.

Conclusions

This study shows that nearly half of patients with ES have a genetic background being in most cases secondary to IEI, and therefore, a molecular evaluation should be offered to all patients.

Case Report: Deficiency of Adenosine Deaminase 2 Presenting With Overlapping Features of Autoimmune Lymphoproliferative Syndrome and Bone Marrow Failure

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease associated with a highly variable clinical presentation, such as vasculitis, inflammation, and hematologic manifestations. Some associations of clinical features can mimic autoimmune lymphoproliferative syndrome (ALPS). We report a case of a female patient who fulfilled the 2009 National Institute of Health revised criteria for ALPS and received a delayed diagnosis of DADA2. During her childhood, she suffered from autoimmune hemolytic anemia, immune thrombocytopenia, and chronic lymphoproliferation, which partially responded to multiple lines of treatments and were followed, at 25 years of age, by pulmonary embolism, septic shock, and bone marrow failure with myelodysplastic evolution. The patient died from the progression of pulmonary disease and multiorgan failure. Two previously unreported variants of gene ADA2/CECR1 were found through next-generation sequencing analysis, and a pathogenic role was demonstrated through a functional study. A single somatic STAT3 mutation was also found. Clinical phenotypes encompassing immune dysregulation and marrow failure should be evaluated at the early stage of diagnostic work-up with an extended molecular evaluation. A correct genetic diagnosis may lead to a precision medicine approach consisting of the use of targeted treatments or early hematopoietic stem cell transplantation.