Bruton's tyrosine kinase (BTK), encoded by the BTK gene, is a cytoplasmic protein critical in B cell development. Mutations in the BTK gene cause X-linked agammaglobulinemia (XLA), a primary immunodeficiency with characteristically low or absent B cells and antibodies. This report describes a five year-old boy who presented with otitis externa, arthritis, reduced immunoglobulins and no B cells. Flow cytometry showed undetectable monocyte BTK expression. Sequencing revealed a novel mutation at exon 13 of the BTK gene which created a de novo splice site with a proximal 5 nucleotide loss resulting in a truncated BTK protein. The patient still suffered from ear infection despite intravenous immunoglobulin replacement therapy. In this study, mosaicism was seen only in the mother's genomic DNA. These results suggest that a combination of flow cytometry and BTK gene analysis is important for XLA diagnosis and carrier screening.
X-linked agammaglobulinemia (XLA) is a rare genetic disorder caused by mutations in the Bruton's tyrosine kinase (BTK) gene. These mutations cause defects in early B cell development. A patient with no circulating B cells and low serum immunoglobulin isotypes was studied as were his mother and sister. Monocyte BTK protein expression was evaluated by flow cytometry. The mutation was determined using PCR and followed by sequencing. Flow cytometry showed the patient lacked BTK protein expression in his monocytes while the mother and sister had 62% and 40% of the monocytes showing BTK protein expressions respectively. The patient had a novel base substitution in the first nucleotide of intron 9 in the BTK gene, and the mutation was IVS9+1GX-linked agammaglobulinemia and may be used for subsequent genetic counseling, carrier detection and prenatal diagnosis.
X-linked agammaglobulinemia (XLA) is a rare genetic disorder, caused by mutations in BTK (Bruton's Tyrosine Kinase) gene. Deep high-throughput RNA sequencing (RNA-Seq) approach was utilized to explore the possible differences in transcriptome profiles of primary monocytes in XLA patients compared with healthy subjects. Our analysis revealed the differences in expression of 1,827 protein-coding genes, 95 annotated long non-coding RNAs (lncRNAs) and 20 novel lincRNAs between XLA patients and healthy subjects. GO and KEGG pathway analysis of differentially expressed (DE) protein-coding genes showed downregulation of several innate immune-related genes and upregulation of oxidative phosphorylation and apoptosis-related genes in XLA patients compared to the healthy subjects. Moreover, the functional prediction analysis of DE lncRNAs revealed their potential role in regulating the monocytes cell cycle and apoptosis in XLA patients. Our results suggested that BTK mutations may contribute to the dysregulation of innate immune system and increase susceptibility to apoptosis in monocytes of XLA patients. This study provides significant finding on the regulation of BTK gene in monocytes and the potential for development of innovative biomarkers and therapeutic monitoring strategies to increase the quality of life in XLA patients.
BACKGROUND: Chronic granulomatous disease (CGD) is a rare primary immunodeficiency (PID) caused by a dysfunctional respiratory burst enzyme NADPH-oxidase. The concurrence of Klinefelter’s Syndrome (KS) and CGD would be extremely rare.
OBJECTIVE: We describe the study of a family where the youngest male child had X-linked CGD (X-CGD) while his older brother was both an X-CGD carrier and a Klinefelter.
METHODS: Flow cytometry was used to study respiratory burst and gp91-phox expression, while genetic investigation was done by RT-PCR, PCR and X-chromosome short tandem repeat (X-STR) analysis.
RESULTS: The Dihydrorhodamine (DHR) assay showed the patient’s neutrophils failed to produce a respiratory burst, while both the mother and an older brother showed a bimodal response. gp91-phox expression was absent in the patient’s neutrophils, and bimodal in the mother’s and brother’s neutrophils. The patient’s cDNA showed a C>T change at nucleotide 676 of the CYBB gene. The same change was seen in the patient’s gDNA, while the brother and mother were heterozygous, with C and T, in this position. The c.676C>T is a nonsense mutation that leads to premature termination of the gp91-phox protein. The brother karyotyped as 47, XXY and X chromosome analysis showed that he had inherited both his mother’s X chromosomes.
CONCLUSIONS: This study showed that the patient had gp91-phox deficient CGD while his older brother was a CGD carrier and a Klinefelter, who had inherited both his mother’s X chromosomes. This is the first report of such a concurrence in an individual, and argues for family members to be included in PID studies.
Key words: Chronic granulomatous disease, CYBB, gp91-phox, Klinefelter’s syndrome NADPHoxidase
Phosphoglycerate kinase (PGK) deficiency is an X-linked neurometabolic genetic disorder with variable systemic manifestations. So far, only one patient with retinal anomalies has been reported, but no visual electrophysiology findings were described. We report the first description of visual electrophysiology in a child with PGK deficiency. This provides further information for the site of involvement in the eye.
Dimorphism in peripheral blood film was noted in a 16 year old Malay boy with anemia who was eventually diagnosed with X-linked sideroblastic anemia. A mutation in ALAS2 S568G was identified which has not been described previously in a Malay ethnic group.