Genetic analysis of CYBB gene in 26 korean families with X-linked chronic granulomatous disease

Hematologically important mutations: X-linked chronic granulomatous disease (fourth update)

Chronic granulomatous disease (CGD) is an immunodeficiency disorder affecting about 1 in 250,000 individuals. CGD patients suffer from severe bacterial and fungal infections. The disease is caused by a lack of superoxide production by the leukocyte enzyme NADPH oxidase. Superoxide and subsequently formed other reactive oxygen species (ROS) are instrumental in killing phagocytosed micro-organisms in neutrophils, eosinophils, monocytes and macrophages. The leukocyte NADPH oxidase is composed of five subunits, of which the enzymatic component is gp91^phox, also called Nox2. This protein is encoded by the CYBB gene on the X chromosome. Mutations in this gene are found in about 70% of all CGD patients in Europe and in about 20% in countries with a high ratio of parental consanguinity. This article lists all mutations identified in CYBB and should therefore help in genetic counseling of X-CGD patients' families. Moreover, apparently benign polymorphisms in CYBB are also given, which should facilitate the recognition of disease-causing mutations. In addition, we also include some mutations in G6PD, the gene on the X chromosome that encodes glucose-6-phosphate dehydrogenase, because inactivity of this enzyme may lead to shortage of NADPH and thus to insufficient activity of NADPH oxidase. Severe G6PD deficiency can induce CGD-like symptoms.

Identification of Cytochrome b-245, beta-chain gene mutations, and clinical presentations in Iranian patients with X-linked chronic granulomatous disease

Background

X‐linked chronic granulomatous disease (X‐CGD) is an immunodeficiency disorder caused by defects in the gp91^phox subunit that leads to life‐threatening infections. We aimed to identify CYBB gene mutations and study clinical phenotypes in Iranian patients with probable X‐CGD.

Methods

We studied four unrelated Iranian patients with probable X‐CGD and their families recruited in several years. We isolated genomic DNA from whole blood and performed Sanger sequencing in the CYBB gene's coding and flanking regions. We also performed pathogenicity predictions using in silico tools.

Results

We detected four different mutations, including a novel insertion mutation in exon 5 (p.Ile117AsnfsX6), in the patient. Bioinformatics analysis confirmed the pathogenic effect of this mutation. We predicted protein modeling and demonstrated lost functional domains. The patient with the insertion mutation presented pneumonia and acute sinusitis during his life. We also detected three other known nonsense mutations (p.Arg157Ter, p.Arg226Ter, and p.Trp424Ter) in the CYBB gene. The patient with p.Arg157Ter developed lymphadenitis and pneumonia. Moreover, the patient with inflammatory bowel disease showed p.Arg226Ter and the patient with tuberculosis presented p.Trp424Ter. We detected different clinical features in the patients compared to other Iranian patients with the same mutations.

Conclusion

Our results expand the genetic database of patients with X‐CGD from Iran and make it much easier and faster to identify patients with X‐CGD. Our results also help to detect carriers and enable prenatal diagnosis in high‐risk families as a cost‐effective strategy.

Gene analysis of seven cases of primary immunodeficiency

BACKGROUND

Primary immune deficiency diseases (PID) are a group of potentially serious disorders in which inherited defects in the immune system lead to increased infections. This paper explores the clinical characteristics and pathogenic gene mutation of PID.

METHODS

The clinical data, clinical manifestations, and gene sequencing results of seven children were analyzed.

RESULTS

Among the seven children, six were male, and one was female, aged from 4 months to 13 years old. All of them had a history of repeated infection and pneumonia. High throughput sequencing (NGS) showed that the BTK gene of case 1 had c.1921c > t mutation; the BTK gene of case 2 had c.906-908del splice site mutation; the BTK gene of case 3 had c.718delg mutation; the cybb gene of case 4 had c.469c > t mutation; the IL2RG gene of case 5 had c.202g > A mutation; the STAT1 gene of case 6 had c.854a > G mutation; the case 7 had c.718delg mutation. There was c.1154c > t mutation in the STAT1 gene. Cases 1, 3, 6 and 7 were new mutations, and cases 2, 4, and 5 were inherited from mothers.

CONCLUSIONS

In clinical cases of children with recurrent infection, the immunologic index is abnormal, so we need to be highly aware of the possibility of PID, and timely high-throughput sequencing is helpful for the diagnosis.

"Clinical Aspects of Chronic Granulomatous Disease in Upper Egypt"

Chronic granulomatous disease (CGD) is a rare inherited primary immunodeficiency disorder that affects phagocytes and is characterized by a marked increased susceptibility to severe bacterial and fungal infections. We aimed to describe the clinical presentations of pediatric patients with CGD in Upper Egypt and to identify the defective component of NADPH oxidase. Pediatric patients diagnosed with CGD within one year from January 2018 to January 2019 were enrolled in the study. Patient history, clinical and laboratory investigations were carried out, including nitroblue tetrazolium test and flow cytometry DHR analysis. Infectious microorganisms were isolated from infected sites to identify the causative agents and their resistance profile. A total of 15 patients were diagnosed with CGD. Failure to thrive and lymphadenopathy were the most common presentations. The median age of clinical onset was 1.17 years of age. The most common gene mutations were observed in the CYBA gene. All cases showed pulmonary infections followed by abscesses. Staphylococcus aureus and Klebsiella pneumoniae were the most frequently isolated bacterial pathogens, Aspergillus spp and Candida spp were isolated from fungal infections. 4/15 (26.7%) children died due to severe serious infections. We concluded that CGD is common in Upper Egypt, and we recommend raising the awareness and testing for CGD in pediatric patients with recurrent or persistent infections, especially those with a familiar history of similar manifestations to avoid delays in proper diagnosis and deterioration of cases. Abbreviations: CGD: chronic granulomatous disease; XL: X-linked; AR: autosomal recessive.

Common Infections and Target Organs Associated with Chronic Granulomatous Disease in Iran

Recurrent severe bacterial and fungal infections are characteristic features of the rare genetic immunodeficiency disorder chronic granulomatous disease (CGD). The disease usually manifests within the first years of life with an incidence of 1 in approximately 200,000 live births. The incidence is higher in Iran and Morocco where it reaches 1.5 per 100,000 live births. Mutations have been described in the 5 subunits of NADPH oxidase, mostly in gp91phox and p47phox, with fewer mutations reported in p67phox, p22phox, and p40phox. These mutations cause loss of superoxide production in phagocytic cells. CYBB, the gene encoding the large gp91phox subunit of the transmembrane component cytochrome b558 of the NADPH oxidase complex, is localized on the X-chromosome. Genetic defects in CYBB are responsible for the disease in the majority of male CGD patients. CGD is associated with the development of granulomatous reactions in the skin, lungs, bones, and lymph nodes, and chronic infections may be seen in the liver, gastrointestinal tract, brain, and eyes. There is usually a history of repeated infections, including inflammation of the lymph glands, skin infections, and pneumonia. There may also be a persistent runny nose, inflammation of the skin, and inflammation of the mucous membranes of the mouth. Gastrointestinal problems can also occur, including diarrhea, abdominal pain, and perianal abscesses. Infection of the bones, brain abscesses, obstruction of the genitourinary tract and/or gastrointestinal tract due to the formation of granulomatous tissue, and delayed growth are also symptomatic of CGD. The prevention of infectious complications in patients with CGD involves targeted prophylaxis against opportunistic microorganisms such as Staphylococcus aureus, Klebsiella spp., Salmonella spp. and Aspergillus spp. In this review, we provide an update on organ involvement and the association with specific isolated microorganisms in CGD patients.