Background Recurrent bacterial and fungal infections, eczema and elevated serum IgE levels characterize patients with the hyper-IgE syndrome (HIES). Known genetic causes for HIES are mutations in STAT3 and DOCK8, involved in signal transduction pathways. However, glycosylation defects have not been described in HIES. One crucial enzyme in the glycosylation pathway is Phosphoglucomutase 3 (PGM3), which catalyzes a key step in the synthesis of UDP-GlcNAc which is required for the biosynthesis of N-glycans. Objective To elucidate the genetic cause in HIES patients who do not carry mutations in STAT3 or DOCK8. Methods After establishing a linkage interval by SNP-chip genotyping and homozygosity mapping in two HIES families from Tunisia, mutational analysis was performed with selector-based, high-throughput sequencing. Protein expression was analyzed by Western blotting and glycosylation was profiled by mass spectrometry. Results Mutational analysis of candidate genes in a 11.9 Mb linkage region on chromosome 6 shared by two multiplex families identified two homozygous mutations in PGM3 which segregated with the disease status and followed a recessive inheritance trait. The mutations predict amino acid changes in Phosphoglucomutase-3; PGM3 (p.Glu340del and p.Leu83Ser). A third homozygous mutation (p.Asp502Tyr) and the p.Leu83Ser variant were identified in two other affected families, respectively. These hypomorphic mutations have impact on the biosynthetic reactions involving UDP-GlcNAc. Glycomic analysis revealed an aberrant glycosylation pattern in leukocytes demonstrated by a reduced level of tri-/tetra-antennary N-glycans. T cell proliferation and differentiation was impaired in patients. Most patients showed developmental delay and many had psychomotor retardation. Conclusion Impairment of PGM3 function leads to a novel primary (inborn) error of development and immunity, as biallelic hypomorphic mutations are associated with impaired glycosylation and a hyper-IgE-like phenotype.

Background Mutations in DOCK8 cause a combined immunodeficiency (CID) also classified as autosomal-recessive hyper-IgE syndrome (HIES). Recognizing patients with CID / HIES is of clinical importance due to a difference in prognosis and management. Objectives Define the clinical features that distinguish DOCK8 deficiency from other forms of HIES and CIDs; study the mutational spectrum of DOCK8 deficiency; and report on the frequency of specific clinical findings. Methods Eighty-two patients from 60 families with CID and the phenotype of autosomal-recessive HIES with (64 patients) and without (18 patients) DOCK8 mutations were studied. Support vector machines were used to compare clinical data from 35 patients with DOCK8 deficiency with 10 AR-HIES patients without a DOCK8 mutation and 64 patients with STAT3 mutations. Results DOCK8-deficient patients had a median IgE of 5,201 IU, high eosinophil levels of usually at least 800/µl (92% of patients), and low levels of IgM (62%). About 20% of patients were lymphopenic, mainly due to low CD4+ and CD8+ T cells. Fewer than half of the patients tested produced normal specific antibody responses to recall antigens. Bacterial (84%), viral (78%), and fungal (70%) infections were frequently observed. Skin abscesses (60%) and allergies (73%) were common clinical problems. In contrast to STAT3 deficiency, there were few pneumatoceles, bone fractures, and teething problems. Mortality was high (34%). A combination of five clinical features was helpful in distinguishing patients with DOCK8 mutations from those with STAT3 mutations. Conclusions DOCK8 deficiency is likely in patients with severe viral infections, allergies, and/or low IgM levels, who have a diagnosis of HIES plus hypereosinophilia and upper respiratory tract infections in the absence of parenchymal lung abnormalities, retained primary teeth, and minimal trauma fractures.

Chronic mucocutaneous candidiasis (CMC) is defined as recurrent or persistent infection of the skin, nails, and/or mucosae with commensalCandidaspecies. The first genetic etiology of isolated CMC—autosomal recessive (AR) IL-17 receptor A (IL-17RA) deficiency—was reported in 2011, in a single patient. We report here 21 patients with complete AR IL-17RA deficiency, including this first patient. Each patient is homozygous for 1 of 12 different IL-17RA alleles, 8 of which create a premature stop codon upstream from the transmembrane domain and have been predicted and/or shown to prevent expression of the receptor on the surface of circulating leukocytes and dermal fibroblasts. Three other mutant alleles create a premature stop codon downstream from the transmembrane domain, one of which encodes a surface-expressed receptor. Finally, the only known missense allele (p.D387N) also encodes a surface-expressed receptor. All of the alleles tested abolish cellular responses to IL-17A and -17F homodimers and heterodimers in fibroblasts and to IL-17E/IL-25 in leukocytes. The patients are currently aged from 2 to 35 y and originate from 12 unrelated kindreds. All had their first CMC episode by 6 mo of age. Fourteen patients presented various forms of staphylococcal skin disease. Eight were also prone to various bacterial infections of the respiratory tract. Human IL-17RA is, thus, essential for mucocutaneous immunity toCandidaandStaphylococcus, but otherwise largely redundant. A diagnosis of AR IL-17RA deficiency should be considered in children or adults with CMC, cutaneous staphylococcal disease, or both, even if IL-17RA is detected on the cell surface.

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Leukocyte adhesion deficiency (LAD) is an immunodeficiency caused by defects in the adhesion of leukocytes (especially neutrophils) to the blood vessel wall. As a result, patients with LAD suffer from severe bacterial infections and impaired wound healing, accompanied by neutrophilia. In LAD-I, mutations are found in ITGB2, the gene that encodes the β subunit of the β2 integrins. This syndrome is characterized directly after birth by delayed separation of the umbilical cord. In the rare LAD-II disease, the fucosylation of selectin ligands is disturbed, caused by mutations in SLC35C1, the gene that encodes a GDP-fucose transporter of the Golgi system. LAD-II patients lack the H and Lewis Lea and Leb blood group antigens. Finally, in LAD-III (also called LAD-I/variant) the conformational activation of the hematopoietically expressed β integrins is disturbed, leading to leukocyte and platelet dysfunction. This last syndrome is caused by mutations in FERMT3, encoding the kindlin-3 protein in all blood cells that is involved in the regulation of β integrin conformation.

SUMMARY Cytokines are classically thought to stimulate downstream signaling pathways through monotonic activation of receptors. We describe a severe anemia resulting from a homozygous mutation in the cytokine erythropoietin (EPO, R150Q). Surprisingly, the EPO R150Q mutant shows only a mild reduction in affinity for its receptor, but has altered binding kinetics. The EPO mutant is less effective at stimulating erythroid cell proliferation and differentiation, even at maximally potent concentrations. While the EPO mutant can stimulate effectors such as STAT5 to a similar extent as the wild type ligand, there is reduced JAK2-mediated phosphorylation of select downstream targets. This impairment in downstream signaling mechanistically arises from altered receptor dimerization dynamics due to extracellular binding changes. These results demonstrate how variation in a single cytokine can lead to biased downstream signaling and can thereby cause human disease. Moreover, we have defined a distinct treatable form of anemia through mutation identification and functional studies.

Background: While autoimmunity and hyperinflammation secondary to recombinase activating gene (RAG) deficiency have been associated with delayed diagnosis and even death, our current understanding is limited primarily to small case series. Objective: Understand the frequency, severity, and treatment responsiveness of autoimmunity and hyperinflammation in RAG deficiency. Methods: In reviewing the literature and our own database, we identified 85 patients with RAG deficiency, reported between 2001 and 2016, and compiled the largest case series to date of 63 patients with prominent autoimmune and/or hyperinflammatory pathology. Results: Diagnosis of RAG deficiency was delayed a median of 5 years from the first clinical signs of immune dysregulation. The majority of patients (55.6%) presented with more than one autoimmune or hyperinflammatory complication, with the most common etiologies being cytopenias (84.1%), granulomas (23.8%), and inflammatory skin disorders (19.0%). Infections, including live viral vaccinations, closely preceded the onset of autoimmunity in 28.6% of cases. Autoimmune cytopenias had early onset (median 1.9, 2.1, and 2.6 years for autoimmune hemolytic anemia (AIHA), immune thrombocytopenia (ITP) and autoimmune neutropenia (AN), respectively) and were refractory to intravenous immunoglobulin, steroids, and rituximab in the majority of cases (64.7%, 73.7%, and 71.4% for AIHA, ITP, and AN, respectively). Evans syndrome specifically was associated with lack of response to first-line therapy. Treatment-refractory autoimmunity/hyperinflammation prompted hematopoietic stem cell transplantation in 20 patients. Conclusions: Autoimmunity/hyperinflammation can be a presenting sign of RAG deficiency and should prompt further evaluation. Multi-lineage cytopenias are often refractory to immunosuppressive treatment and may require hematopoietic cell transplantation for definitive management.

Somekh and colleagues identify CD137, a member of the tumor necrosis factor superfamily, as a novel cause of immunodeficiency associated with a risk of autoimmunity and lymphoid malignancy.