Heterozygous FOXN1 Variants Cause Low TRECs and Severe T Cell Lymphopenia, Revealing a Crucial Role of FOXN1 in Supporting Early Thymopoiesis.

FOXN1 is the master regulatory gene of thymic epithelium development. FOXN1 deficiency leads to thymic aplasia, alopecia, and nail dystrophy, accounting for the nude/severe combined immunodeficiency (nu/SCID) phenotype in humans and mice. We identified several newborns with low levels of T cell receptor excision circles (TRECs) and T cell lymphopenia at birth, who carried heterozygous loss-of-function FOXN1 variants. Longitudinal analysis showed persistent T cell lymphopenia during infancy, often associated with nail dystrophy. Adult individuals with heterozygous FOXN1 variants had in most cases normal CD4+ but lower than normal CD8+ cell counts. We hypothesized a FOXN1 gene dosage effect on the function of thymic epithelial cells (TECs) and thymopoiesis and postulated that these effects would be more prominent early in life. To test this hypothesis, we analyzed TEC subset frequency and phenotype, early thymic progenitor (ETP) cell count, and expression of FOXN1 target genes (Ccl25, Cxcl12, Dll4, Scf, Psmb11, Prss16, and Cd83) in Foxn1nu/+ (nu/+) mice and age-matched wild-type (+/+) littermate controls. Both the frequency and the absolute count of ETP were significantly reduced in nu/+ mice up to 3 weeks of age. Analysis of the TEC compartment showed reduced expression of FOXN1 target genes and delayed maturation of the medullary TEC compartment in nu/+ mice. These observations establish a FOXN1 gene dosage effect on thymic function and identify FOXN1 haploinsufficiency as an important genetic determinant of T cell lymphopenia at birth.

Outcomes after Allogeneic Transplant in Patients with Wiskott-Aldrich Syndrome.

Wiskott-Aldrich syndrome (WAS) is a rare X-linked disorder characterized by a triad of immunodeficiency, eczema, and thrombocytopenia. Currently, hematopoietic stem cell transplantation (HSCT) is the most reliable curative treatment with excellent results for patients with HLA-matched family or unrelated donors. However, even after fully myeloablative preparative regimens, mixed donor chimerism is a potential concern. We performed a retrospective chart review of 12 children who underwent allogeneic HSCT for WAS to report our experience. The median age at transplant was 10.5 months (range, 3 to 39). The median nucleated cell dose from the marrow was 4.55 × 109/kg (range, .3 to 7.9). The median times to neutrophil and platelet engraftment were 19 days (range, 13 to 27) and 18.5 days (range, 12 to 31), respectively. The rate of overall survival was 92% with median follow-up of 67 months (range, 3 to 146). Two patients developed grade IV acute graft-versus-host disease, and 1 died on day +99. Five of 12 patient's (42%) had mixed donor chimerism (range, 12% to 85%) at day +180. None of the pretransplant patient parameters was predictive of mixed chimerism. Nonetheless, of these 5 patients, 2 had normalization of the platelet count despite the mixed chimerism, 2 had full donor chimerism after receiving a second transplant with the same donor, and 1 remains transfusion dependent awaiting a second transplant. Hence, even with a significant rate of mixed chimerism, HSCT provides substantial benefit to WAS patients, with excellent overall survival.

Improved diagnostic clarity in shrimp allergic non-dust-mite sensitized patients.

BACKGROUND: Allergen specific immunoglobulin E (sIgE) levels predictive of shrimp allergy have not been identified, but these may be helpful in identifying patients at risk for shrimp-induced allergic reactions. OBJECTIVE: This study sought to identify component resolved diagnostic tests useful for diagnosis of shrimp allergy in patients with or without house-dust mite (HDM) sensitization to the major allergen cysteine protease (Der p 1). METHODS: Patients with positive skin-prick test (SPT) results and/or sIgE values were recruited. Shrimp allergy was classified by oral food challenge (OFC) or by a clear history of anaphylaxis after shrimp ingestion. Patients with shrimp allergy and patients who were tolerant were further classified based on HDM sensitivity (Der p 1 > 0.35 kUA/L). Testing for sIgE to total shrimp, and shrimp and HDM components was performed. The Fisher exact test, Wilcoxon sum rank test, and receiver operating characteristics analyses were used to compare sIgE levels in patients with allergy and patients who were tolerant. RESULTS: Of 79 patients recruited, 12 patients with shrimp allergy (7 with positive OFC results and 5 with a history of anaphylaxis) and 18 patients who were shrimp tolerant were enrolled. Of the patients not HDM sensitized, sIgE levels to shrimp (10.5 kUA/L, p = 0.012) and Der p 10 (4.09 kUA/L, p = 0.035) were higher in patients with shrimp allergy. Shrimp sIgE of ≥3.55 kUA/L had 100% diagnostic sensitivity and 85.7% specificity (receiver operating characteristic 0.94 [0.81, 1.0] 95% CI) and Der p 10 sIgE levels of ≥3.98 kUA/L had a diagnostic sensitivity of 80% and specificity of 100% (receiver operating characteristic 0.86 [0.57, 1.0] 95% CI) for prediction of clinical reactivity. CONCLUSION: HDM sensitization influences shrimp and HDM component sIgE levels and, consequently, their diagnostic accuracy in shrimp allergy. In our series, in the patients who were non-HDM sensitized, a shrimp sIgE level of >3.55 kUA/L showed 100% sensitivity and, Der p 10 sIgE of >3.98 kUA/L showed 100% specificity for the diagnosis of shrimp allergy. These levels may not be applicable to every patient and, therefore, may not obviate the need for OFC.

Primary immunodeficiency diseases: Genomic approaches delineate heterogeneous Mendelian disorders.

BACKGROUND: Primary immunodeficiency diseases (PIDDs) are clinically and genetically heterogeneous disorders thus far associated with mutations in more than 300 genes. The clinical phenotypes derived from distinct genotypes can overlap. Genetic etiology can be a prognostic indicator of disease severity and can influence treatment decisions. OBJECTIVE: We sought to investigate the ability of whole-exome screening methods to detect disease-causing variants in patients with PIDDs. METHODS: Patients with PIDDs from 278 families from 22 countries were investigated by using whole-exome sequencing. Computational copy number variant (CNV) prediction pipelines and an exome-tiling chromosomal microarray were also applied to identify intragenic CNVs. Analytic approaches initially focused on 475 known or candidate PIDD genes but were nonexclusive and further tailored based on clinical data, family history, and immunophenotyping. RESULTS: A likely molecular diagnosis was achieved in 110 (40%) unrelated probands. Clinical diagnosis was revised in about half (60/110) and management was directly altered in nearly a quarter (26/110) of families based on molecular findings. Twelve PIDD-causing CNVs were detected, including 7 smaller than 30 Kb that would not have been detected with conventional diagnostic CNV arrays. CONCLUSION: This high-throughput genomic approach enabled detection of disease-related variants in unexpected genes; permitted detection of low-grade constitutional, somatic, and revertant mosaicism; and provided evidence of a mutational burden in mixed PIDD immunophenotypes.

Health-Related Quality of Life in Adult Patients with Common Variable Immunodeficiency Disorders and Impact of Treatment.

PURPOSE: Common variable immunodeficiency disorder (CVID) is a primary immunodeficiency disease (PIDD) often associated with severe and chronic infections. Patients commonly receive immunoglobulin (Ig) treatment to reduce the cycle of recurrent infection and improve physical functioning. However, how Ig treatment in CVID affects quality of life (QOL) has not been thoroughly evaluated. The purpose of a recent Immune Deficiency Foundation (IDF) mail survey was to assess the factors that are associated with QOL in patients with CVID receiving Ig treatment. METHODS: A 75-question survey developed by the IDF and a 12-item Short Form Health Survey (SF-12) to assess QOL were mailed to adults with CVID. Mean SF-12 scores were compared between patients with CVID and the general US adult population normative sample. RESULTS: Overall, 945 patients with CVID completed the surveys. More than half of the patients (54.9%) received intravenous Ig and 44.9% received subcutaneous Ig treatment. Patients with CVID had significantly lower SF-12 scores compared with the general US population regardless of sex or age (p < 0.05). Route of IgG replacement did not dramatically improve QOL. SF-12 scores were highest in patients with CVID who have well-controlled PIDD, lacked physical impairments, were not bothered by treatment, and received Ig infusions at home. CONCLUSION: These data provide insight into what factors are most associated with physical and mental health, which can serve to improve QOL in patients in this population. Improvements in QOL can result from early detection of disease, limiting digestive system disease, attention to fatigue, and implementation of an individual treatment plan for the patient.

Angiostrongylus cantonensis Infection: A Cause of Fever of Unknown Origin in Pediatric Patients.

Fever of unknown origin (FUO) in children is frequently caused by infectious diseases. Angiostrongylus cantonensis, while a primary cause of eosinophilic meningitis, is rarely a cause of FUO. We present 2 pediatric cases of FUO caused by Angiostrongylus cantonensis acquired in Houston, Texas, outside its usual geographic distribution.

Pulmonologist perspectives regarding diagnosis and management of primary immunodeficiency diseases.

BACKGROUND: The time from symptom onset to diagnosis for patients with primary immunodeficiency diseases (PIDD) is an average of 12 years, but prompt diagnosis and treatment can promote best outcomes. OBJECTIVE: Because the manifestations of PIDD are often sinopulmonary in nature, patients with undiagnosed PIDD are frequently referred to pulmonologists. This study sought to identify opportunities among these specialists to improve diagnosis and clinical management of patients with PIDD. METHODS: A survey was sent to American Medical Association and American Osteopathic Association members whose specialty was pulmonology. Responses were compared with those from a historical survey of 71 subspecialist immunologists (American Academy of Allergy, Asthma Immunology members who devoted 10% of their practice to patients with PIDD). RESULTS: The surveys were returned by 485 pulmonologists, 49% of whom had diagnosed at least one patient with PIDD. In comparison with subspecialist immunologists, fewer pulmonologists were aware of the professional PIDD diagnosis and management guidelines and fewer followed up patients with various PIDDs. Pulmonologists and subspecialist immunologists also differed in the practice of prescribing prophylactic antibiotics and immunoglobulin replacement and in avoiding live viral vaccines. CONCLUSION: Differences in the diagnosis and treatment of patients with PIDD between these two groups of specialists revealed areas in which PIDD-focused educational initiatives may be helpful for pulmonologists.

Perceived Health in Patients with Primary Immune Deficiency.

PURPOSE: Perceived health (PH) is a subjective measure of global health of individuals. While many studies have evaluated outcomes in patients with primary immune deficiency (PID), published literature evaluating PH among patients with PID is sparse. We evaluated the results of the largest self-reported survey of patients with PID to determine the factors that may contribute to differences in PH. METHODS: Data from a National Survey of Patients with Primary Immune Deficiency Diseases conducted by the Immune Deficiency Foundation was studied. Multivariate logistic regression was employed for data analysis. RESULTS: Thirty percent of the patients perceived their health status as excellent or very good (EVG), 31 % as good (G), and 39 % as fair, poor or very poor (P). Older patients were less likely to have EVG-PH compared to G-PH. Ones with college degrees were more likely to have P-PH compared to G-PH, and less likely to have EVG-PH. Patients who were acutely ill and hospitalized in the past 12 months, ones with limited activity, and chronic diseases, were more likely to have P-PH compared to G-PH. Patients with "on demand" access to specialty care and ones on regular IVIG had higher OR of having EVG-PH as opposed to G-PH. Patients cared for mostly by an immunologist were less likely to have P-PH compared to G-PH. CONCLUSIONS: Our results emphasize the importance of PH in clinical practice. We suggest that recognizing the factors that drive PH in patients with PID is important for the development of disease prevention and health promotion programs, and delivery of appropriate health and social services to individuals with PID.

A 15-year-old boy with severe combined immunodeficiency, fungal infection, and weight gain.

Hematopoietic stem cell transplantation (HSCT) outcomes in X-linked severe combined immune deficiency are most effective when performed with patients <3 months of age and without coexisting morbidity, and with donor cells from a matched sibling. Even under such favorable circumstances, outcomes can be suboptimal, and full cellular engraftment may not be complete, which results in poor B or natural killer cell function. Protein losing enteropathies can accompany persistent immune deficiency disorders with resultant low serum globulins (immunoglobulin A [IgA], IgG, IgM) and lymphopenia. Patients with immune disorders acquire infections that can be predicted by their immune dysfunction. Fungal infections are typically noted in neutropenic (congenital or acquired) and T-cell deficient individuals. Coexisting fungal infections are rare, even in hosts who are immunocompromised, and they require careful evaluation. Antifungal treatment may result in drug-drug interactions with significant complications.

Cord blood transplantation for nonmalignant disorders: early functional immunity and high survival.

There is no consensus on the best donor for children with nonmalignant disorders and immune deficiencies in the absence of a matched related donor (MRD). We evaluated the 2-year overall survival (OS) after umbilical cord blood transplantation (UCBT) in patients with nonmalignant disorders from 2009 to 2020 enrolled in a prospective clinical trial using either 5/6 or 6/6 UCB as the cell source. Patients receive a fully ablative busulfan, cyclophosphamide, and fludarabine without serotherapy. Fifty-five children were enrolled, median age 5 months (range, 1-111 months); primary immune deficiency (45), metabolic (5), hemophagocytic lymphohistiocytosis (1), and hematologic disorders (4). Twenty-six patients had persistent infections before transplant. Nineteen of them (34%) were 6/6 matched, and 36 (66%) were 5/6 human leukocyte antigen-matched. The OS at 2 years was 91% (95% cumulative incidence, 79-96), with a median follow-up of 4.3 years. The median time to neutrophil and platelet recovery were 17 days (range, 5-39 days) and 37 days (range, 20-92 days), respectively. All but one evaluable patient achieved full donor chimerism. The cumulative incidence of acute GVHD grades 2-4 on day 100 was 16% (n = 9). All patients with viral infections at the time of transplant cleared the infection at a median time of 54 days (range, 44-91 days). All evaluable patients underwent correction of their immune or metabolic defects. We conclude that in the absence of MRD, UCBT following myeloablative conditioning without serotherapy is an excellent curative option in young children with nonmalignant disorders. This trial has been registered at www.clinicaltrials.gov as NCT00950846.

PI Prob: A risk prediction and clinical guidance system for evaluating patients with recurrent infections.

BACKGROUND: Primary immunodeficiency diseases represent an expanding set of heterogeneous conditions which are difficult to recognize clinically. Diagnostic rates outside of the newborn period have not changed appreciably. This concern underscores a need for novel methods of disease detection. OBJECTIVE: We built a Bayesian network to provide real-time risk assessment about primary immunodeficiency and to facilitate prescriptive analytics for initiating the most appropriate diagnostic work up. Our goal is to improve diagnostic rates for primary immunodeficiency and shorten time to diagnosis. We aimed to use readily available health record data and a small training dataset to prove utility in diagnosing patients with relatively rare features. METHODS: We extracted data from the Texas Children's Hospital electronic health record on a large population of primary immunodeficiency patients (n = 1762) and appropriately-matched set of controls (n = 1698). From the cohorts, clinically relevant prior probabilities were calculated enabling construction of a Bayesian network probabilistic model(PI Prob). Our model was constructed with clinical-immunology domain expertise, trained on a balanced cohort of 100 cases-controls and validated on an unseen balanced cohort of 150 cases-controls. Performance was measured by area under the receiver operator characteristic curve (AUROC). We also compared our network performance to classic machine learning model performance on the same dataset. RESULTS: PI Prob was accurate in classifying immunodeficiency patients from controls (AUROC = 0.945; p<0.0001) at a risk threshold of ≥6%. Additionally, the model was 89% accurate for categorizing validation cohort members into appropriate International Union of Immunological Societies diagnostic categories. Our network outperformed 3 other machine learning models and provides superior transparency with a prescriptive output element. CONCLUSION: Artificial intelligence methods can classify risk for primary immunodeficiency and guide management. PI Prob enables accurate, objective decision making about risk and guides the user towards the appropriate diagnostic evaluation for patients with recurrent infections. Probabilistic models can be trained with small datasets underscoring their utility for rare disease detection given appropriate domain expertise for feature selection and network construction.

Outcomes of patients with severe combined immunodeficiency treated with hematopoietic stem cell transplantation with and without preconditioning.

BACKGROUND: The effect of pretransplantation conditioning on the long-term outcomes of patients receiving hematopoietic stem cell transplantation for severe combined immunodeficiency (SCID) has not been completely determined. OBJECTIVE: We sought to assess the outcomes of 23 mostly conditioned patients with SCID and compare their outcomes with those of 25 previously reported nonconditioned patients with SCID who underwent transplantation. METHODS: In the present study we reviewed the medical records of these 23 consecutive, mostly conditioned patients with SCID who underwent transplantation between 1998 and 2007. RESULTS: Eighteen patients (median age at transplantation, 10 months; range, 0.8-108 months) received haploidentical mismatched related donor, matched unrelated donor, or mismatched unrelated donor transplants, 17 of whom received pretransplantation conditioning (with 1 not conditioned); 13 (72%) patients engrafted with donor cells and survive at a median of 3.8 years (range, 1.8-9.8 year); 5 (38%) of 13 patients require intravenous immunoglobulin; and 6 of 6 age-eligible children attend school. Of 5 recipients (median age at transplantation, 7 months; range, 2-23 months) of matched related donor transplants, all 5 engrafted and survive at a median of 7.5 years (range, 1.5-9.5 year), 1 recipient requires intravenous immunoglobulin, and 3 of 3 age-eligible children attend school. Gene mutations were known in 16 cases: mutation in the common gamma chain of the IL-2 receptor (IL2RG) in 7 patients, mutation in the alpha chain of the IL-7 receptor (IL7RA) in 4 patients, mutation in the recombinase-activating gene (RAG1) in 2 patients, adenosine deaminase deficiency (ADA) in 2 patients, and adenylate kinase 2 (AK2) in 1 patient. Early outcomes and quality of life of the previous nonconditioned versus the present conditioned cohorts were not statistically different, but longer-term follow-up is necessary for confirmation. CONCLUSIONS: Hematopoietic stem cell transplantation in patients with SCID results in engraftment, long-term survival, and a good quality of life for the majority of patients with or without pretransplantation conditioning.

Case Report: Secondary Hemophagocytic Lymphohistiocytosis With Disseminated Infection in Chronic Granulomatous Disease-A Serious Cause of Mortality.

Chronic granulomatous disease (CGD) is a primary immune deficiency due to defects in phagocyte respiratory burst leading to severe and life-threatening infections. Patients with CGD also suffer from disorders of inflammation and immune dysregulation including colitis and granulomatous lung disease, among others. Additionally, patients with CGD may be at increased risk of systemic inflammatory disorders such as hemophagocytic lymphohistiocytosis (HLH). The presentation of HLH often overlaps with symptoms of systemic inflammatory response syndrome (SIRS) or sepsis and therefore can be difficult to identify, especially in patients with a primary immune deficiency in which incidence of infection is increased. Thorough evaluation and empiric treatment for bacterial and fungal infections is necessary as HLH in CGD is almost always secondary to infection. Simultaneous treatment of infection with anti-microbials and inflammation with immunosuppression may be needed to blunt the hyperinflammatory response in secondary HLH. Herein, we present a series of X-linked CGD patients who developed HLH secondary to or with concurrent disseminated CGD-related infection. In two patients, CGD was a known diagnosis prior to development of HLH and in the other two CGD was diagnosed as part of the evaluation for HLH. Concurrent infection and HLH were fatal in three; one case was successfully treated, ultimately receiving hematopoietic stem cell transplantation. The current literature on presentation, diagnosis, and treatment of HLH in CGD is reviewed.

Family Physician Perspectives on Primary Immunodeficiency Diseases.

Primary immunodeficiency diseases (PIDs) include over 250 diverse disorders. The current study assessed management of PID by family practice physicians. The American Academy of Allergy, Asthma, and Immunology Primary Immunodeficiency Committee and the Immune Deficiency Foundation conducted an incentivized mail survey of family practice physician members of the American Medical Association and the American Osteopathic Association in direct patient care. Responses were compared with subspecialist immunologist responses from a similar survey. Surveys were returned by 528 (of 4500 surveys mailed) family practice physicians, of whom 44% reported following ≥1 patient with PID. Selective immunoglobulin A deficiency (21%) and chronic granulomatous disease (11%) were most common and were followed by significantly more subspecialist immunologists (P < 0.05). Use of intravenously administered immunoglobulin and live viral vaccinations across PID was significantly different (P < 0.05). Few family practice physicians were aware of professional guidelines for diagnosis and management of PID (4 vs. 79% of subspecialist immunologists, P < 0.05). Family practice physicians will likely encounter patients with PID diagnoses during their career. Differences in how family practice physicians and subspecialist immunologists manage patients with PID underscore areas where improved educational and training initiatives may benefit patient care.