The diagnosis of severe combined immunodeficiency: Implementation of the PIDTC 2022 Definitions

BACKGROUND

Shearer et al in 2014 articulated well-defined criteria for the diagnosis and classification of severe combined immunodeficiency (SCID) as part of the Primary Immune Deficiency Treatment Consortium's (PIDTC's) prospective and retrospective studies of SCID.

OBJECTIVE

Because of the advent of newborn screening for SCID and expanded availability of genetic sequencing, revision of the PIDTC 2014 Criteria was needed.

METHODS

We developed and tested updated PIDTC 2022 SCID Definitions by analyzing 379 patients proposed for prospective enrollment into Protocol 6901, focusing on the ability to distinguish patients with various SCID subtypes.

RESULTS

According to PIDTC 2022 Definitions, 18 of 353 patients eligible per 2014 Criteria were considered not to have SCID, whereas 11 of 26 patients ineligible per 2014 Criteria were determined to have SCID. Of note, very low numbers of autologous T cells (<0.05 × 109/L) characterized typical SCID under the 2022 Definitions. Pathogenic variant(s) in SCID-associated genes was identified in 93% of patients, with 7 genes (IL2RG, RAG1, ADA, IL7R, DCLRE1C, JAK3, and RAG2) accounting for 89% of typical SCID. Three genotypes (RAG1, ADA, and RMRP) accounted for 57% of cases of leaky/atypical SCID; there were 13 other rare genotypes. Patients with leaky/atypical SCID were more likely to be diagnosed at more than age 1 year than those with typical SCID lacking maternal T cells: 20% versus 1% (P < .001). Although repeat testing proved important, an initial CD3 T-cell count of less than 0.05 × 109/L differentiated cases of typical SCID lacking maternal cells from leaky/atypical SCID: 97% versus 7% (P < .001).

CONCLUSIONS

The PIDTC 2022 Definitions describe SCID and its subtypes more precisely than before, facilitating analyses of SCID characteristics and outcomes.

Hematopoietic Cell Transplantation in Patients With Primary Immune Regulatory Disorders (PIRD): A Primary Immune Deficiency Treatment Consortium (PIDTC) Survey

Primary Immune Regulatory Disorders (PIRD) are an expanding group of diseases caused by gene defects in several different immune pathways, such as regulatory T cell function. Patients with PIRD develop clinical manifestations associated with diminished and exaggerated immune responses. Management of these patients is complicated; oftentimes immunosuppressive therapies are insufficient, and patients may require hematopoietic cell transplant (HCT) for treatment. Analysis of HCT data in PIRD patients have previously focused on a single gene defect. This study surveyed transplanted patients with a phenotypic clinical picture consistent with PIRD treated in 33 Primary Immune Deficiency Treatment Consortium centers and European centers. Our data showed that PIRD patients often had immunodeficient and autoimmune features affecting multiple organ systems. Transplantation resulted in resolution of disease manifestations in more than half of the patients with an overall 5-years survival of 67%. This study, the first to encompass disorders across the PIRD spectrum, highlights the need for further research in PIRD management.

Primary immune regulatory disorders for the pediatric hematologist and oncologist: A case-based review

An array of monogenic immune defects marked by autoimmunity, lymphoproliferation, and hyperinflammation rather than infections have been described. Primary immune regulatory disorders pose a challenge to pediatric hematologists and oncologists. This paper focuses on primary immune regulatory disorders including autoimmune lymphoproliferative syndrome (ALPS) and ALPS-like syndromes, immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) and IPEX-like disorders, common variable immunodeficiency (CVID), CVID-like, and late-onset combined immunodeficiency (CID) disorders. Hyperinflammatory disorders and those associated with increased susceptibility to lymphoid malignancies are also discussed. Using a case-based approach, a review of clinical pearls germane to the clinical and laboratory evaluation as well as the treatment of these disorders is provided.

High Rates of Community and Hospital Acquired Infections in Patients with Cellular Immunodeficiencies

PURPOSE

Patients with primary immunodeficiency diseases (PID) are perceived to be at high risk for acquiring as well as developing complications from infections. There is little data describing the infection type and frequency these patients may acquire in the community or during hospital admissions. Data is critically needed in order to inform best practices on how to protect these vulnerable patients.

METHODS

This is a retrospective study which included PID patients who were discharged from Children's National Health System (CNHS) from January 1, 2011, through August 31, 2017, and were assigned a discharge diagnosis code indicating PID. Hospitalizations that occurred in the study period were reviewed to extract information on the type of infections upon admission and during hospitalization. The rate of hospital acquired infections (HAIs) was calculated by the number of HAIs divided by the total number of days between date of admission and date of discharge or receiving the first bone marrow transplant, whichever the one came first. The rates were then compared to the HAI rate among oncology patients receiving treatment at CNHS during the same study period.

RESULTS

During this study period, 33 PID patients were admitted 80 times for a total of 1855 patient days. Of these 80 admissions, 31 were due to an infection. Ten of the 31 admissions with severe combined immunodeficiency disease (SCID) were infection related, 4/4 in ectodermal dysplasia with immunodeficiency due to gain of function mutation (IkappaBalpha) patients, 8/10 in Wiskott-Aldrich patients, 1/2 in STAT3 mutation patients, 1/1 in Hyper IGM patient, 1/5 in severe chronic active EBV (SCAEBV) patients, 1/1 NK defect, 2/21 in primary hemophagocytic lymphohistiocytosis patients, 3/4 chronic granulomatous disease, and 0/1 congenital neutropenia. HAI occurred in 11 out of 80 admissions (13.75%). Patients with SCID had the highest HAI rate of 13.09 per 1000 patient days, followed by SCAEBV (11.10), IkappaBalpha (6.58), and Wiskott-Aldrich (4.91). Comparing to oncology patients in which the HAI rate was 0.92 per 1000 patient days. SCID patients had 11.7 (95% confidence interval 3.7-29; p < 0.001) and T cell defects excluding SCID had 4.8 (95% CI 1.0-14.8; p = 0.03) times greater risk of acquiring an infection during a hospitalization.

CONCLUSIONS

Patients with severe T cell defects such as SCID are at greater risk for infections in the community and in hospital settings. Additional infection prevention measures are likely needed when caring for these patients in a clinic or as an inpatient. Further studies are urgently needed to determine the most appropriate measures for these patients.