HSCT provides effective treatment for lymphoproliferative disorders in children with primary immunodeficiency

How to recognize inborn errors of immunity in a child presenting with a malignancy: guidelines for the pediatric hemato-oncologist

Inborn errors of immunity (IEI) are a group of disorders caused by genetically determined defects in the immune system, leading to infections, autoimmunity, autoinflammation and an increased risk of malignancy. In some cases, a malignancy might be the first sign of an underlying IEI. As therapeutic strategies might be different in these patients, recognition of the underlying IEI by the pediatric hemato-oncologist is important. This article, written by a group of experts in pediatric immunology, hemato-oncology, pathology and genetics, aims to provide guidelines for pediatric hemato-oncologists on how to recognize a possible underlying IEI and what diagnostic tests can be performed, and gives some consideration to treatment possibilities.

Inborn errors of immunity: Recent progress

Recent advances in the field of inborn errors of immunity (IEIs) have been wide in scope, including progress in mechanisms of disease, diagnosis, and management. New gene defects affecting the immune response continue to be reported, as many as 26 in the year 2020. It was noted that the presentation of IEIs might not include recurrent infections in 9% of cases, and that current diagnostic methods can identify molecular causes in 92% of patients with severe combined immunodeficiency. Progress in immunopathogenesis explained mechanisms leading to symptoms of autosomal-recessive hyper-IgE syndrome. There was an emphasis on research in primary antibody deficiencies. The benefit of antibiotic prophylaxis to reduce the frequency of infections was demonstrated in these patients. The regimen of rituximab and azathioprine or mycophenolate was proven effective for chronic granulocytic interstitial pneumonia. The efficacy and adverse events of hematopoietic stem cell transplant in different IEI conditions were reported, as well as different strategies to improve outcomes, supporting its use in immunodeficiency and immunodysregulatory syndromes. The recent pandemic of coronavirus disease 2019 affected patients with IEIs, in particular those with deficiency in the interferon-mediated activation of the immune response. Initial data suggest that coronavirus disease 2019 vaccines might elicit anti-coronavirus disease 2019-neutralizing antibody responses in some patients with IEI conditions.

The paradigm of hematological malignant versus non-malignant manifestations, driven by primary immunodeficiencies: a complex interplay

Hematological malignancies (HM) developed on underlying primary immunodeficiencies (PID) are rare and of unusual features. Differentiating between malignant and non-malignant lymphoproliferation in cases of pediatric hematology and oncology and revealing their molecular predisposition demonstrate the complex interplay between PID and HM. We retrospectively studied a case series of seven pediatric patients, all with PID with manifestations raising suspicion for HM or hypereosinophilic syndrome (HES) or confirmed HM of lymphoid origin. Combined immunodeficiency (CID) without detection of a known mutated gene or with ataxia-telangiectasia (AT), STAT3 gain of function (GOF), DOCK8 deficiency, and CTLA4 deficiency were diagnosed in three, one, one, one, and one patient, respectively. Acute lymphoblastic leukemia and Hodgkin lymphoma followed by second primary Burkitt lymphoma were diagnosed in one patient with CID each, while lymphomatoid granulomatosis in one patient with AT. Lymphoproliferative disease occurred in STAT3 GOF, CTLA4 deficiency and CID, one patient each, and idiopathic HES in DOCK8 deficiency (median age at presentation of PID or any hematological manifestation: four years). Four patients underwent hematopoietic cell transplantation (HCT) for STAT3 GOF, DOCK8 deficiency and CID in one, one, and two cases, respectively (median age: 10 years). At the last follow-up, all transplanted patients were alive. Reporting on patients' phenotype, genotype and course of disease shed light on the prevalence, characteristics, and pathophysiology of HM complicating PID. Discriminating the non-yet malignant lymphoproliferation from its malignant equivalent on the same pathophysiology background proved of additional value. Outcomes of PID after HCT, herein reported, are favorable.

Lifelong Immune Modulation Versus Hematopoietic Cell Therapy for Inborn Errors of Immunity

Advances in diagnosis of inborn errors of immunity (IEI) and an understanding of the molecular and immunologic mechanisms of these disorders have led to both the development of new therapies and improved approaches to hematopoietic cell transplantation (HCT). For example, monoclonal antibodies (mAbs) and small molecules, such as Janus tyrosine kinase inhibitors, that can modulate immunologic pathways have been designed for or repurposed for management of IEI. A better understanding of molecular mechanisms of IEI has led to use of drugs typically considered "immunosuppressive" to modulate the immune response, such as mammalian target of rapamycin inhibitors in disorders of phosphoinositide 3-kinase gain of function. Since the first HCT in a patient with severe combined immunodeficiency (SCID) in 1968, transplantation strategies have improved, with more than 90% probability of survival after allogeneic HCT in SCID and hence HCT is now the therapeutic standard for SCID and many other IEI. When tailoring treatment for IEI, multiple disease-specific and individual factors should be considered. In diseases such as SCID or agammaglobulinemia, the choice between HCT or medical management is straightforward. However, in many IEI, the choice between the options is challenging. This review focuses on the factors that should be taken into account in the quest for the optimal treatment for patients with IEI.

The Possibilities of Immunotherapy for Children with Primary Immunodeficiencies Associated with Cancers

Many primary immunodeficiencies (PIDs) are recognised as being associated with malignancies, particularly lymphoid malignancies, which represent the highest proportion of cancers occurring in conjunction with this underlying condition. When patients present with genetic errors of immunity, clinicians must often reflect on whether to manage antitumoral treatment conventionally or to take a more personalised approach, considering possible existing comorbidities and the underlying status of immunodeficiency. Recent advances in antitumoral immunotherapies, such as monoclonal antibodies, antigen-specific adoptive cell therapies or compounds with targeted effects, potentially offer significant opportunities for optimising treatment for those patients, especially with lymphoid malignancies. In cases involving PIDs, variable oncogenic mechanisms exist, and opportunities for antitumoral immunotherapies can be considered accordingly. In cases involving a DNA repair defect or genetic instability, monoclonal antibodies can be proposed instead of chemotherapy to avoid severe toxicity. Malignancies secondary to uncontrolled virus-driven proliferation or the loss of antitumoral immunosurveillance may benefit from antivirus cell therapies or allogeneic stem cell transplantation in order to restore the immune antitumoral caretaker function. A subset of PIDs is caused by gene defects affecting targetable signalling pathways directly involved in the oncogenic process, such as the constitutive activation of phosphoinositol 3-kinase/protein kinase B (PI3K/AKT) in activated phosphoinositide 3-kinase delta syndrome (APDS), which can be settled with PI3K/AKT inhibitors. Therefore, immunotherapy provides clinicians with interesting antitumoral therapeutic weapons to treat malignancies when there is an underlying PID.