Digenic inheritance of IL-36RA and SEC61A1 mutations underlies generalized pustular psoriasis with hypogammaglobulinemia.

We report a female patient presenting with generalized pustular psoriasis and hypogammaglobulinemia due to digenic mutations in IL-36RA and SEC61A1. The patient presented with recurrent fevers, elevated inflammatory markers, hepatosplenomegaly, and recurrent sinopulmonary infections in the context of hypogammaglobulinemia which improved on immunoglobulin replacement. This report demonstrates how digenic inheritance leads to complex phenotypes, and illustrates the importance of following an unbiased approach to identifying variants, especially in patients with atypical clinical presentations.

Multisystem inflammation and susceptibility to viral infections in human ZNFX1 deficiency.

BACKGROUND: Recognition of viral nucleic acids is one of the primary triggers for a type I interferon-mediated antiviral immune response. Inborn errors of type I interferon immunity can be associated with increased inflammation and/or increased susceptibility to viral infections as a result of dysbalanced interferon production. NFX1-type zinc finger-containing 1 (ZNFX1) is an interferon-stimulated double-stranded RNA sensor that restricts the replication of RNA viruses in mice. The role of ZNFX1 in the human immune response is not known. OBJECTIVE: We studied 15 patients from 8 families with an autosomal recessive immunodeficiency characterized by severe infections by both RNA and DNA viruses and virally triggered inflammatory episodes with hemophagocytic lymphohistiocytosis-like disease, early-onset seizures, and renal and lung disease. METHODS: Whole exome sequencing was performed on 13 patients from 8 families. We investigated the transcriptome, posttranscriptional regulation of interferon-stimulated genes (ISGs) and predisposition to viral infections in primary cells from patients and controls stimulated with synthetic double-stranded nucleic acids. RESULTS: Deleterious homozygous and compound heterozygous ZNFX1 variants were identified in all 13 patients. Stimulation of patient-derived primary cells with synthetic double-stranded nucleic acids was associated with a deregulated pattern of expression of ISGs and alterations in the half-life of the mRNA of ISGs and also associated with poorer clearance of viral infections by monocytes. CONCLUSION: ZNFX1 is an important regulator of the response to double-stranded nucleic acids stimuli following viral infections. ZNFX1 deficiency predisposes to severe viral infections and a multisystem inflammatory disease.

Hypomorphic variants in AK2 reveal the contribution of mitochondrial function to B-cell activation.

BACKGROUND: The gene AK2 encodes the phosphotransferase adenylate kinase 2 (AK2). Human variants in AK2 cause reticular dysgenesis, a severe combined immunodeficiency with agranulocytosis, lymphopenia, and sensorineural deafness that requires hematopoietic stem cell transplantation for survival. OBJECTIVE: We investigated the mechanisms underlying recurrent sinopulmonary infections and hypogammaglobulinemia in 15 patients, ranging from 3 to 34 years of age, from 9 kindreds. Only 2 patients, both of whom had mildly impaired T-cell proliferation, each had a single clinically significant opportunistic infection. METHODS: Patient cells were studied with next-generation DNA sequencing, tandem mass spectrometry, and assays of lymphocyte and mitochondrial function. RESULTS: We identified 2 different homozygous variants in AK2. AK2G100S and AK2A182D permit residual protein expression, enzymatic activity, and normal numbers of neutrophils and lymphocytes. All but 1 patient had intact hearing. The patients' B cells had severely impaired proliferation and in vitro immunoglobulin secretion. With activation, the patients' B cells exhibited defective mitochondrial respiration and impaired regulation of mitochondrial membrane potential and quality. Although activated T cells from the patients with opportunistic infections demonstrated impaired mitochondrial function, the mitochondrial quality in T cells was preserved. Consistent with the capacity of activated T cells to utilize nonmitochondrial metabolism, these findings revealed a less strict cellular dependence of T-cell function on AK2 activity. Chemical inhibition of ATP synthesis in control T and B cells similarly demonstrated the greater dependency of B cells on mitochondrial function. CONCLUSIONS: Our patients demonstrate the in vivo sequelae of the cell-specific requirements for the functions of AK2 and mitochondria, particularly in B-cell activation and antibody production.

DOCK8 Deficiency Presenting as an IPEX-Like Disorder.

PURPOSE: The dedicator of cytokinesis 8 (DOCK8) deficiency is an autosomal recessive-combined immunodeficiency whose clinical spectra include recurrent infections, autoimmunity, malignancies, elevated serum IgE, eczema, and food allergies. Here, we report on patients with loss of function DOCK8 mutations with profound immune dysregulation suggestive of an immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX)-like disorder. METHODS: Immunophenotyping of lymphocyte subpopulations and analysis of DOCK8 protein expression were evaluated by flow cytometry. T regulatory (Treg) cells were isolated by cell sorting, and their suppressive activity was analyzed by flow cytometry. Gene mutational analysis was performed by whole-exome and Sanger sequencing. RESULTS: Patient 1 (P1) presented at 10 months of age with chronic severe diarrhea and active colitis in the absence of an infectious trigger, severe eczema with elevated serum IgE, and autoimmune hemolytic anemia, suggestive of an IPEX-related disorder. Whole-exome sequencing revealed a homozygous nonsense mutation in DOCK8 at the DOCK-homology region (DHR)-1 (c.1498C>T; p. R500X). Patient P2, a cousin of P1 who carries the same DOCK8 nonsense mutation, presented with eczema and recurrent ear infections in early infancy, and she developed persistent diarrhea by 3 years of age. Patient P3 presented with lymphoproliferation, severe eczema with allergic dysregulation, and chronic diarrhea with colitis. She harbored a homozygous loss of function DOCK8 mutation (c.2402 -1G→A). Treg cell function was severely compromised by both DOCK8 mutations. CONCLUSION: DOCK8 deficiency may present severe immune dysregulation with features that may overlap with those of IPEX and other IPEX-like disorders.

Acetaminophen Inhibits the Neutrophil Oxidative Burst: Implications for Diagnostic Testing.

BACKGROUND: Chronic granulomatous disease is a primary immunodeficiency characterized by recurrent bacterial and fungal infections, granuloma formation, and inflammatory disease. Impaired neutrophil oxidative function is an essential diagnostic criterion. In vitro exposure of neutrophils to acetaminophen, a commonly used over-the-counter medication, has been associated with reduced neutrophil oxidative function. The clinical implications of acetaminophen intake for dihydrorhodamine (DHR) testing remain unknown. OBJECTIVE: To evaluate the effect of in vivo administration of therapeutic doses of acetaminophen on DHR diagnostic testing. METHODS: We performed DHR testing in 15 healthy adults before and after administering a single dose of acetaminophen. We retrospectively reviewed 195 DHR test results from hospitalized patients who had received acetaminophen, nonsteroidal anti-inflammatory drug, or corticosteroid before testing. RESULTS: DHR testing result was abnormal in 100% (n = 15) of healthy adults 2 hours after acetaminophen intake. We identified 195 instances of DHR testing less than or equal to 72 hours after acetaminophen ingestion in hospitalized patients who did not have chronic granulomatous disease. DHR results were abnormal in 43 of 195 cases (22.1%). Frequency of false-positive testing was increased in patients who received acetaminophen within 24 hours of testing, and in patients who received more than 1 dose of acetaminophen. Nonsteroidal anti-inflammatory drug and corticosteroid intakes were not associated with abnormal DHR result. CONCLUSIONS: Patients treated with acetaminophen have decreased neutrophil oxidative burst as measured by DHR testing. To avoid falsely abnormal testing for chronic granulomatous disease, patients should be advised to avoid acetaminophen for at least 24 hours before DHR testing.