BACKGROUND:Patients with partial DiGeorge syndrome (pDGS) can present with immune dysregulation, the most common being autoimmune cytopenia (AIC). There is a lack of consensus on the approach to type, combination, and timing of therapies for AIC in pDGS. Recognition of immune dysregulation early in pDGS clinical course may help individualize treatment and prevent adverse outcomes from chronic immune dysregulation. OBJECTIVES:Objectives of this study were to characterize the natural history, immune phenotype, and biomarkers in pDGS with AIC. METHODS:Data on clinical presentation, disease severity, immunological phenotype, treatment selection, and response for patients with pDGS with AIC were collected via retrospective chart review. Flow cytometric analysis was done to assess T and B cell subsets, including biomarkers of immune dysregulation. RESULTS:Twenty-nine patients with the diagnosis of pDGS and AIC were identified from 5 international institutions. Nineteen (62%) patients developed Evan's syndrome (ES) during their clinical course and twenty (69%) had antibody deficiency syndrome. These patients demonstrated expansion in T follicular helper cells, CD19hiCD21lo B cells, and double negative cells and reduction in CD4 naïve T cells and regulatory T cells. First-line treatment for 17/29 (59%) included corticosteroids and/or high-dose immunoglobulin replacement therapy. Other overlapping therapies included eltrombopag, rituximab, and T cell immunomodulators. CONCLUSIONS:AIC in pDGS is often refractory to conventional AIC treatment paradigms. Biomarkers may have utility for correlation with disease state and potentially even response to therapy. Immunomodulating therapies could be initiated early based on early immune phenotyping and biomarkers before the disease develops or significantly worsens.

In the era of newborn screening (NBS) for severe combined immunodeficiency (SCID) and the possibility of gene therapy (GT), it is important to link SCID phenotype to the underlying genetic disease. In western countries, X-linked interleukin 2 receptor gamma chain (IL2RG) and adenosine deaminase (ADA) deficiency SCID are two of the most common types of SCID and can be treated by GT. As a challenge, both IL2RG and ADA genes are highly polymorphic and a gene-based diagnosis may be difficult if the variant is of unknown significance or if it is located in non-coding areas of the genes that are not routinely evaluated with exon-based genetic testing (e.g., introns, promoters, and the 5'and 3' untranslated regions). Therefore, it is important to extend evaluation to non-coding areas of a SCID gene if the exon-based sequencing is inconclusive and there is strong suspicion that a variant in that gene is the cause for disease. Functional studies are often required in these cases to confirm a pathogenic variant. We present here two unique examples of X-linked SCID with variable immune phenotypes, where IL2R gamma chain expression was detected and no pathogenic variant was identified on initial genetic testing. Pathogenic IL2RG variants were subsequently confirmed by functional assay of gamma chain signaling and maternal X-inactivation studies. We propose that such tests can facilitate confirmation of suspected cases of X-linked SCID in newborns when initial genetic testing is inconclusive. Early identification of pathogenic IL2RG variants is especially important to ensure eligibility for gene therapy.

Most infants with severe combined immunodeficiency (SCID) can be identified early with TREC-based newborn screening (NBS). We present a case of an infant with atypical presentation of SCID resulting in a delayed diagnosis. Retrospective chart review. A Florida (FL)-born infant from a midwife-attended home birth was referred for a specialist immunology consultation at 9 months of age after recurrent infections, failure to thrive and PJP pneumonitis. Immune phenotyping at 9 months revealed absence of naïve T cells with absent proliferation to mitogens and anti-CD3/IL-2. Extreme oligoclonal repertoire of CD3+ T cells (474 cells/mm3) supported a diagnosis of atypical SCID. Review of records showed that the infant's only timely NBS sample was of insufficient quantity for the FL-NBS panel. A much later NBS specimen obtained at 8 months of age showed a normal TREC value. In light of the conflicting clinical/immunological presentation and 8-mo TREC result, extramural TREC analysis of the two NBS specimens (post-birth and 8-mo) was performed in Massachusetts. The post-birth specimen showed undetectable TREC however the 8-mo specimen was normal. At 11 months, a third NBS specimen was obtained; both FL and MA assays confirmed undetectable TREC. The patient developed HHV-6 viremia, which further delayed hematopoietic stem cell transplantation. Early diagnosis of SCID requires multidisciplinary cooperation. Timely replacement of a poor quality specimen might have ensured an earlier diagnosis. Identity testing of the 8-mo specimen remains warranted. Clinical vigilance and awareness for late and/or leaky presentation of SCID should continue even in the era of SCID newborn screening.

Hypereosinophilia is a nonspecific but important clinical finding. While there are many possible etiologies, malignancy should be considered especially in those with severely elevated eosinophil counts. Here we present a child with hypereosinophilia who was found to have acute lymphoblastic leukemia. Clinical examinations, laboratory evaluation, imaging studies, and bone marrow biopsy. This adolescent male initially presented with abdominal pain, vomiting, diarrhea, splenomegaly, and increased WBC 120,000 cells/uL with an eosinophil count 98,300 cells/uL. Chest CT revealed scattered nodular opacities with ground-glass appearance. Infectious studies excluded parasitic infection. Immunoglobulin and lymphocyte quantities were normal as were evaluation for T cell clones and other lymphoproliferative disorders. Initial bone marrow biopsy revealed hypercellular marrow with a granulocytic left shift and marked eosinophilia (47.5% eosinophils) without evidence of an acute leukemic process. Assessment for FIP1L1-PDGFRA fusion was negative. A course of steroids was initiated and weaned over three months, in which he was only mildly responsive. Shortly thereafter, he developed Bell's palsy and continued hypereosinophilia (4,760 cells/uL). Repeat bone marrow evaluation demonstrated a 15% precursor B-cell lymphoblast population in the setting of eosinophilic hyperplasia. Although he did not meet strict diagnostic criteria for B-cell leukemia, he had an expanding lymphoblast population representing an evolving leukemia. He was initiated on the COG protocol AALL1131. Acute lymphoblastic leukemias are among the most common childhood malignancies. However, hypereosinophilia as a presenting sign is relatively rare but may indicate a worse prognosis. This case demonstrates the importance of maintaining high suspicion for malignancy in children with hypereosinophilia.