Human RIPK1 deficiency causes combined immunodeficiency and inflammatory bowel diseases.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is a critical regulator of cell death and inflammation, but its relevance for human disease pathogenesis remains elusive. Studies of monogenic disorders might provide critical insights into disease mechanisms and therapeutic targeting of RIPK1 for common diseases. Here, we report on eight patients from six unrelated pedigrees with biallelic loss-of-function mutations in RIPK1 presenting with primary immunodeficiency and/or intestinal inflammation. Mutations in RIPK1 were associated with reduced NF-κB activity, defective differentiation of T and B cells, increased inflammasome activity, and impaired response to TNFR1-mediated cell death in intestinal epithelial cells. The characterization of RIPK1-deficient patients highlights the essential role of RIPK1 in controlling human immune and intestinal homeostasis, and might have critical implications for therapies targeting RIPK1.

A RAB27A duplication in several cases of Griscelli syndrome type 2: An explanation for cases lacking a genetic diagnosis.

Griscelli syndrome type 2 (GS2) is a rare and often fatal autosomal recessive, hyperinflammatory disorder. It is associated with hypopigmentation of the skin and the hair, resulting in the characteristic pigment accumulation and clumping in the hair shaft. Loss-of-function mutations in RAB27A, resulting from point mutations, short indel, or large deletions, account for all the cases reported to date. However, several GS2 cases originating from Saudi Arabia lack a genetic diagnosis. Here, we report on a new RAB27A genetic anomaly observed in seven Saudi Arabia families that had remained negative after extensive molecular genomic DNA testing. Linkage analysis and targeted sequencing of the RAB27A genomic region in several of these patients led to the identification of a common homozygous tandem duplication of 38 kb affecting exon 2-5 and resulting in a premature stop codon. The pathogenic effect of this duplication was confirmed by a cDNA analysis and functional assays. The identification of microhomology flanking the breakpoint site suggests a possible underlying mechanism.

Mycobacterial disease in patients with chronic granulomatous disease: A retrospective analysis of 71 cases.

BACKGROUND: Chronic granulomatous disease (CGD) is a rare primary immunodeficiency caused by inborn errors of the phagocyte nicotinamide adenine dinucleotide phosphate oxidase complex. From the first year of life onward, most affected patients display multiple, severe, and recurrent infections caused by bacteria and fungi. Mycobacterial infections have also been reported in some patients. OBJECTIVE: Our objective was to assess the effect of mycobacterial disease in patients with CGD. METHODS: We analyzed retrospectively the clinical features of mycobacterial disease in 71 patients with CGD. Tuberculosis and BCG disease were diagnosed on the basis of microbiological, pathological, and/or clinical criteria. RESULTS: Thirty-one (44%) patients had tuberculosis, and 53 (75%) presented with adverse effects of BCG vaccination; 13 (18%) had both tuberculosis and BCG infections. None of these patients displayed clinical disease caused by environmental mycobacteria, Mycobacterium leprae, or Mycobacterium ulcerans. Most patients (76%) also had other pyogenic and fungal infections, but 24% presented solely with mycobacterial disease. Most patients presented a single localized episode of mycobacterial disease (37%), but recurrence (18%), disseminated disease (27%), and even death (18%) were also observed. One common feature in these patients was an early age at presentation for BCG disease. Mycobacterial disease was the first clinical manifestation of CGD in 60% of these patients. CONCLUSION: Mycobacterial disease is relatively common in patients with CGD living in countries in which tuberculosis is endemic, BCG vaccine is mandatory, or both. Adverse reactions to BCG and severe forms of tuberculosis should lead to a suspicion of CGD. BCG vaccine is contraindicated in patients with CGD.

Unbiased targeted next-generation sequencing molecular approach for primary immunodeficiency diseases.

BACKGROUND: Molecular genetics techniques are an essential diagnostic tool for primary immunodeficiency diseases (PIDs). The use of next-generation sequencing (NGS) provides a comprehensive way of concurrently screening a large number of PID genes. However, its validity and cost-effectiveness require verification. OBJECTIVES: We sought to identify and overcome complications associated with the use of NGS in a comprehensive gene panel incorporating 162 PID genes. We aimed to ascertain the specificity, sensitivity, and clinical sensitivity of the gene panel and its utility as a diagnostic tool for PIDs. METHODS: A total of 162 PID genes were screened in 261 patients by using the Ion Torrent Proton NGS sequencing platform. Of the 261 patients, 122 had at least 1 known causal mutation at the onset of the study and were used to assess the specificity and sensitivity of the assay. The remaining samples were from unsolved cases that were biased toward more phenotypically and genotypically complicated cases. RESULTS: The assay was able to detect the mutation in 117 (96%) of 122 positive control subjects with known causal mutations. For the unsolved cases, our assay resulted in a molecular genetic diagnosis for 35 of 139 patients. Interestingly, most of these cases represented atypical clinical presentations of known PIDs. CONCLUSIONS: The targeted NGS PID gene panel is a sensitive and cost-effective diagnostic tool that can be used as a first-line molecular assay in patients with PIDs. The assay is an alternative choice to the complex and costly candidate gene approach, particularly for patients with atypical presentation of known PID genes.

Premature birth, respiratory distress, intracerebral hemorrhage, and silvery-gray hair: differential diagnosis of the 3 types of Griscelli syndrome.

SUMMARY: A preterm neonate, born to consanguineous parents, presented with respiratory distress, intracerebral hemorrhage, and a silvery-gray sheen of the hair and eyelashes. Griscelli syndrome (GS) type 3 was diagnosed after the detection of a novel homozygous mutation of the melanophilin gene. Thus, only the hypopigmentation, but not the patient's other clinical features, were attributable to this form of GS. Differential diagnosis of the various forms of GS must be performed as early as possible as GS2 is associated with a life threatening but curable immune disorder.

A digenic human immunodeficiency characterized by IFNAR1 and IFNGR2 mutations.

Primary immunodeficiencies are often monogenic disorders characterized by vulnerability to specific infectious pathogens. Here, we performed whole-exome sequencing of a patient with disseminated Mycobacterium abscessus, Streptococcus viridians bacteremia, and cytomegalovirus (CMV) viremia and identified mutations in 2 genes that regulate distinct IFN pathways. The patient had a homozygous frameshift deletion in IFNGR2, which encodes the signal transducing chain of the IFN-γ receptor, that resulted in minimal protein expression and abolished downstream signaling. The patient also harbored a homozygous deletion in IFNAR1 (IFNAR1*557Gluext*46), which encodes the IFN-α receptor signaling subunit. The IFNAR1*557Gluext*46 resulted in replacement of the stop codon with 46 additional codons at the C-terminus. The level of IFNAR1*557Gluext*46 mutant protein expressed in patient fibroblasts was comparable to levels of WT IFNAR1 in control fibroblasts. IFN-α-induced signaling was impaired in the patient fibroblasts, as evidenced by decreased STAT1/STAT2 phosphorylation, nuclear translocation of STAT1, and expression of IFN-α-stimulated genes critical for CMV immunity. Pretreatment with IFN-α failed to suppress CMV protein expression in patient fibroblasts, whereas expression of WT IFNAR1 restored IFN-α-mediated suppression of CMV. This study identifies a human IFNAR1 mutation and describes a digenic immunodeficiency specific to type I and type II IFNs.

Invasive mucormycosis in chronic granulomatous disease.

Mucormycosis is a rare opportunistic fungal infection that occurs in certain immunocompromised patients. We present 2 cases of invasive mucormycosis due to Rhizopus spp. in patients with chronic granulomatous disease (CGD) and discuss their clinical presentation, management challenges, and outcomes.

Deficiency of base excision repair enzyme NEIL3 drives increased predisposition to autoimmunity.

Alterations in the apoptosis of immune cells have been associated with autoimmunity. Here, we have identified a homozygous missense mutation in the gene encoding the base excision repair enzyme Nei endonuclease VIII-like 3 (NEIL3) that abolished enzymatic activity in 3 siblings from a consanguineous family. The NEIL3 mutation was associated with fatal recurrent infections, severe autoimmunity, hypogammaglobulinemia, and impaired B cell function in these individuals. The same homozygous NEIL3 mutation was also identified in an asymptomatic individual who exhibited elevated levels of serum autoantibodies and defective peripheral B cell tolerance, but normal B cell function. Further analysis of the patients revealed an absence of LPS-responsive beige-like anchor (LRBA) protein expression, a known cause of immunodeficiency. We next examined the contribution of NEIL3 to the maintenance of self-tolerance in Neil3-/- mice. Although Neil3-/- mice displayed normal B cell function, they exhibited elevated serum levels of autoantibodies and developed nephritis following treatment with poly(I:C) to mimic microbial stimulation. In Neil3-/- mice, splenic T and B cells as well as germinal center B cells from Peyer's patches showed marked increases in apoptosis and cell death, indicating the potential release of self-antigens that favor autoimmunity. These findings demonstrate that deficiency in NEIL3 is associated with increased lymphocyte apoptosis, autoantibodies, and predisposition to autoimmunity.

Inherited IL-12p40 deficiency: genetic, immunologic, and clinical features of 49 patients from 30 kindreds.

Autosomal recessive interleukin (IL)-12 p40 (IL-12p40) deficiency is a rare genetic etiology of mendelian susceptibility to mycobacterial disease (MSMD). We report the genetic, immunologic, and clinical features of 49 patients from 30 kindreds originating from 5 countries (India, Iran, Pakistan, Saudi Arabia, and Tunisia). There are only 9 different mutant alleles of the IL12B gene: 2 small insertions, 3 small deletions, 2 splice site mutations, and 1 large deletion, each causing a frameshift and leading to a premature stop codon, and 1 nonsense mutation. Four of these 9 variants are recurrent, affecting 25 of the 30 reported kindreds, due to founder effects in specific countries. All patients are homozygous and display complete IL-12p40 deficiency. As a result, the patients lack detectable IL-12p70 and IL-12p40 and have low levels of interferon gamma (IFN-γ). The clinical features are characterized by childhood onset of bacille Calmette-Guérin (attenuated Mycobacterium bovis strain) (BCG) and Salmonella infections, with recurrences of salmonellosis (36.4%) more common than recurrences of mycobacterial disease (25%). BCG vaccination led to BCG disease in 40 of the 41 patients vaccinated (97.5%). Multiple mycobacterial infections were rare, observed in only 3 patients, whereas the association of salmonellosis and mycobacteriosis was observed in 9 patients. A few other infections were diagnosed, including chronic mucocutaneous candidiasis (n = 3), nocardiosis (n = 2), and klebsiellosis (n = 1). IL-12p40 deficiency has a high but incomplete clinical penetrance, with 33.3% of genetically affected relatives of index cases showing no symptoms. However, the prognosis is poor, with mortality rates of up to 28.6%. Overall, the clinical phenotype of IL-12p40 deficiency closely resembles that of interleukin 12 receptor ß1 (IL-12Rß1) deficiency. In conclusion, IL-12p40 deficiency is more common than initially thought and should be considered worldwide in patients with MSMD and other intramacrophagic infectious diseases, salmonellosis in particular.