Dysgammaglobulinemia Associated With Glu349del, a Hypomorphic XIAP Mutation.

BACKGROUND: X-linked lymphoproliferative syndrome type 2 is a rare hereditary immunodeficiency caused by mutations in the XIAP gene. This immunodeficiency frequently results in hemophagocytic lymphohistiocytosis, although hypogammaglobulinemia and dysgammaglobulinemia are also common. OBJECTIVE: We identified 17 patients from 12 Japanese families with mutations in XIAP. The Glu349del mutation was observed in 3 patients, each from a different family. Interestingly, these patients exhibited dysgammaglobulinemia but not hemophagocytic lymphohistiocytosis. We conducted an immunological study of patients carrying Glu349del and other mutations to elucidate the pathogenic mechanisms of dysgammaglobulinemia in patients with mutations in the XIAP gene. PATIENTS AND METHODS: We performed an immunological study of 2 patients carrying the Glu349del mutation and 8 patients with other mutations. RESULTS: Flow cytometry showed that the percentage of memory B cells in patients with a mutation in XIAP was lower than that observed in the healthy controls. The patients with the Glu349del mutation had a lower percentage of memory B cells than those with other mutations. Ig production was reduced in patients with the Glu349del mutation. Increased susceptibility to apoptosis was observed in the patients with other mutations. Susceptibility to apoptosis was normal in patients with Glu349del. Microarray analysis indicated that expression of Ig-related genes was reduced in patients with the Glu349del mutation and that the pattern was different from that observed in the healthy controls or patients with other mutations in XIAP. CONCLUSIONS: Patients carrying the Glu349del mutation in the XIAP gene may have a clinically and immunologically distinct phenotype from patients with other XIAP mutations. The Glu349del mutation may be associated with dysgammaglobulinemia.

A Novel Missense Mutation of DKC1 In Dyskeratosis Congenita With Pulmonary Fibrosis.

Dyskeratosis congenita (DC) is a rare inherited multisystem disorder caused by mutations in seven genes involved in telomere biology, with approximately 20% of cases having pulmonary complications. DKC1 mutations exhibit a severe disease phenotype of DC that develops in early childhood. Here, we report a unique case of DC with pulmonary fibrosis diagnosed at the age of 46. A novel missense mutation(p.Arg65Lys) of DKC1 was detected, and predicted to show a weak mutagenic effect. In spite of the steroid and immunosuppressive treatment, he died of an acute exacerbation seven months after the initial visit. This case suggests that mutation subtypes can cause heterogeneity in DC and pulmonary fibrosis.

Paediatric presentation and outcome of congenital protein C deficiency in Japan.

Severe heritable protein C (PC) deficiency is quite rare, although heterozygous PROC mutation is the second leading cause of genetic predisposition to thrombosis in Japanese adults. The aim of the study was to search the optimal management, the paediatric onset and outcomes of PC deficiency were characterized in Japan. The genetic study, postmarketing survey of activated PC(aPC) concentrate (Anact(®)C) and intensive review in Japan for 20 years enabled the analysis of the disease onset, genotype, treatment and prognosis. Symptomatic PC deficiency was determined in 27 Japanese children. All but two patients presented within 16 days after birth (three prenatal and six neonatal onsets). Postnatal-onset cases had normal growth at full-term delivery. Of the 27 patients, 19 suffered intracranial thrombosis or haemorrhage (ICTH) (three foetal hydrocephalies), 16 developed purpura fulminans (PF) and 10 had both at the first presentation. ICTH preceded PF in both affected cases. Low PC activities of 18 mothers and/or 12 fathers indicated 20 inherited PC deficiencies (2 homozygotes, 11 compound heterozygotes and 7 heterozygotes) and seven unidentified causes of PC deficiency. Nine of 11 patients studied had PROC mutations. Four unrelated patients (50%) carried PC nagoya (1362delG). No PC-deficient parents had experienced thromboembolism. Of the 18 patients with aPC therapy, two died and eight evaluable survivors had neurological sequelae. This first comprehensive study of paediatric PC deficiency suggested that perinatal ICTH was the major presentation, occurring earlier than neonatal PF. PC nagoya was prevalent in paediatric, but not adult, patients in Japan. Early maternal screening and optimal PC therapy are required for newborns at risk of PC deficiency.

Exonic deletion of CASP10 in a patient presenting with systemic juvenile idiopathic arthritis, but not with autoimmune lymphoproliferative syndrome type IIa.

Systemic juvenile idiopathic arthritis (s-JIA) is a rare inflammatory disease classified as a subtype of chronic childhood arthritis, manifested by spiking fever, erythematous skin rash, pericarditis and hepatosplenomegaly. The genetic background underlying s-JIA remains poorly defined. To detect copy number variations, we performed single nucleotide polymorphism (SNP) array analysis in 50 patients with s-JIA. We found a 13-kb intragenic deletion of CASP10 in one patient. RT-PCR of the mRNA extracted from the patient's lymphoblastoid cells revealed that CASP10 mRNA was truncated. Sequencing the mRNA revealed that this deletion resulted in a frame shift with an early stop codon. CASP10 is known as a causative gene for autoimmune lymphoproliferative syndrome (ALPS) type IIa, another childhood syndrome of lymphadenopathy and splenomegaly associated with autoimmune haemolytic anaemia and thrombocytopenia. TCR αß(+) CD4/CD8 double-negative T cells in the peripheral blood as a diagnostic marker of ALPS were not high in this patient and lymphocyte apoptosis induced by anti-Fas antibody was normal, denying ALPS in the patient. The father and a sister of the patient showing no symptoms of ALPS or s-JIA, also had the same deletion. Furthermore, we found no other mutations of CASP10 in the other 49 s-JIA patients. These data suggest that the pathogenic significance of CASP10 mutations should be carefully evaluated in s-JIA or even ALPS type IIa in further studies.

Long-term results of the Japanese Childhood Cancer and Leukemia Study Group studies 811, 841, 874 and 911 on childhood acute lymphoblastic leukemia.

We analyzed the long-term outcomes of 1021 patients with acute lymphoblastic leukemia (ALL), enrolled in four successive clinical trials (ALL811, ALL841, ALL874 and ALL911) between 1981 and 1993. All patients received risk-adopted therapy according to leukocyte count and age at the time of diagnosis. The median follow-up durations of the four studies were 17.8 years in ALL811, 15.5 years in ALL841, 11.9 years in ALL874 and 15.8 years in ALL911. Patients' event-free survival (EFS) and overall survival (OS) rates at 12 years were 41.0 and 54.3% in ALL811, 50.2 and 60.2% in ALL841, 57.3 and 64.7% in ALL874, and 63.4 and 71.7% in ALL911, respectively. Thus, cure can become a reality for about 70% of children with ALL. There is, however, still a significant difference in survival outcomes according to risk group. Late effects were observed in 70 patients out of 834 (8.4%); hepatitis and short stature were most commonly reported. Reduction of late adverse effects for all patients and development of new treatment strategies for very-high-risk patients are major issues for upcoming trials to address.

Novel mutations in a Japanese patient with CD19 deficiency.

Common variable immunodeficiency (CVID) is a heterogeneous disorder characterized by recurrent bacterial infections, hypogammaglobulinemia and low to normal numbers of circulating B cells. Mutations in the ICOS, TACI and CD19 genes have recently been identified in <10% of CVID patients. We, herein, describe two novel CD19 gene disruptions in an 8-year-old Japanese boy, who had been clinically diagnosed as having CVID at the age of 5 years. Flow-cytometric analysis demonstrated absence of CD19 and reduced CD21 expression on CD20-postive peripheral blood B cells. Mutation analysis of CD19 revealed a mutation in the splice acceptor site of intron 5 (IVS5-1G>T) of the maternal allele, resulting in skipping of exon 6, and a truncated protein product. The paternal allele was disrupted by a gross deletion encompassing at least the ATP2A1, CD19 and NFATC2IP genes. The patient had a small number of IgD(-) CD27(+) memory B cells, in which somatic mutation were detected. His B cells showed substantial proliferation upon stimulation, but reduced IgG and IgA production in vitro. These findings extend the mutation spectrum of the CD19 deficiency to four, and confirm the homogeneity of the CD19 deficiency as a unique type of CVID.

Expression of Fc gamma and complement receptors in monocytes of X-linked agammaglobulinaemia and common variable immunodeficiency patients.

Recently we reported that monocyte phagocytosis and chemotaxis are impaired in X-linked agammaglobulinaemia (XLA) and common variable immunodeficiency (CVI) patients. Few data exist on the in vivo expression of receptors for the constant region of immunoglobulin (IgG) (Fc gammaR) and complement receptors (CR) in these patients. The objective of this study was to investigate the expression of Fc gammaR and CR on monocytes from XLA and CVI patients and compare it to that of healthy controls. Whole blood samples were obtained from 10 patients with XLA, 12 with CVI and 18 healthy controls. Monocyte phenotype was determined by flow cytometry with gating on CD14+ cells. Surface expression of Fc gammaRI (CD64), Fc gammaRII (CD32) and Fc gammaRIII (CD16), CR1 (CD35) and CR3 (CD11b and CD18) was measured by determination of the proportion of CD14+ cells positive for each receptor and by receptor density. Compared to controls, a significantly higher percentage of CD16 and CD35+ monocytes from XLA (P = 0.002 and P = 0.007, respectively) were observed. The relative fluorescence intensity (RFI) expression of Fc gammaRII (CD32) and Fc gammaRIII (CD16) were significantly lower on CVI monocytes compared to controls (P = 0.001 and P = 0.035, respectively). XLA patients, who have a reduction of Bruton's tyrosine kinase (Btk), showed normal or increased percentages of monocytes expressing Fc gamma and complement receptors. CVI patients, who have normal expression of Btk, showed reduced expression of CD16 and CD32 on monocytes. Inefficient chemotaxis and phagocytosis, reported previously in XLA patients, could be due to defects of cytoplasmatic transduction mechanisms.

Defective Fc-, CR1- and CR3-mediated monocyte phagocytosis and chemotaxis in common variable immunodeficiency and X-linked agammaglobulinemia patients.

Blood monocyte phagocytic functions were evaluated by chemotaxis, phagocytosis, and superoxide anion production in nine patients with common variable immunodeficiency (CVI), eight patients with X-linked agammaglobulinemia (XLA), and in 17 normal subjects. Further laboratory diagnosis included the determination of the Bruton's tyrosine kinase (Btk) protein expression in monocytes using flow cytometry. The analysis of monocyte phagocytic function demonstrated that CR3-, CR1-, and Fc-mediated phagocytosis (p = 0.0001) were significantly decreased in CVI and XLA patients, and chemotaxis of monocytes (p = 0.0082) was reduced in XLA patients. Superoxide anion production, however, did not differ between the CVI, XLA, and the control groups. The cytoplasmic expression of Btk protein in monocytes was normal in CVI patients and decreased or not detected in XLA patients. It is proposed that impaired chemotaxis and phagocytosis by monocytes may be a characteristic of the innate immune system in CVI and XLA patients, providing a new direction for the physiopathology of these immunodeficiencies.

Clinical and mutational characteristics of X-linked agammaglobulinemia and its carrier identified by flow cytometric assessment combined with genetic analysis.

BACKGROUND: X-linked agammaglobulinemia (XLA), caused by mutations in Bruton's tyrosine kinase (BTK ), is the most common form of inherited antibody deficiency. We previously reported that a flow cytometric evaluation of BTK expression in monocytes could easily detect XLA as well as its carrier. OBJECTIVE: Our purpose was to perform further flow cytometric analysis in additional XLA families in Japan. METHODS: In all, 106 hypogammaglobulinemic males (from 91 families) of various ages with a lack of mature B cells (<1%) were investigated. RESULTS: Flow cytometric assessment revealed the deficient BTK expression status in 78 families (93 patients), and mutations in BTK were identified in 76 of 78 families with presumed XLA. Of the patients with normal BTK expression, 2 showed missense mutations in which the normal amount of altered BTK transcript would cause the XLA phenotype. As many as 30% of these patients with XLA were clinically or genetically recognized beyond 5 years of age. Higher concentrations (>300 mg/dL) of serum IgG were evident in the cases diagnosed among adults, seemingly preventing severe infections. Fifty-seven of 70 mothers of patients with BTK deficiency were diagnosed as obligate carriers on the basis of a bimodal BTK expression pattern. Nine of the remaining 13 mothers showing nonmosaic BTK expression had no mutations in 2 alleles; surprisingly, the other 4 mothers had the mutated alleles. CONCLUSIONS: A diagnostic approach based on flow cytometric assessment for XLA should be initially considered in genetic investigation of antibody deficiencies, regardless of the patient's age.

Prognostic impact of CD45 antigen expression in high-risk, childhood B-cell precursor acute lymphoblastic leukemia.

To evaluate the clinical implications of CD45 expression in acute childhood lymphoblastic leukemia (ALL), we measured the CD45 expression of blast cells from 133 untreated patients with childhood B-precursor ALL (n = 118) or T-ALL (n = 15). CD45 expression (> or = 20%) was detected in all 15 cases (100%) of T-ALL, and 101 cases (86%) of B-precursor ALL. In 122 cases, the fluorescence intensity of the CD45 expression was measured as a relative value; the ratio of average linear values (RALV) of CD45 on the blasts to that on CD3-positive T-lymphocytes from the same specimen. The expression was more intense in the T-ALL cases than in the B-precursor ALL cases (RALV, mean +/- SE: T-ALL 0.230 +/- 0.04 vs. pro-B ALL 0.150 +/- 0.012/pre-B ALL 0.153 +/- 0.019, p < 0.05). However, the intensity of the CD10, CD19, CD20 and CD34 antigen immunoreactivity did not correlate with the CD45 expression. Patients with hyperdiploidy (chromosome number > 50) showed significantly lower levels of CD45 expression than patients with t(1;19) or normal karyotypes (RALV, mean +/- SE: 0.081 +/- 0.022 vs. 0.133 +/- 0.03/0.143 +/- 0.019, p < 0.05). Other clinical features such as age, gender and WBC count did not correlate with CD45 expression. The prognostic implications of CD45 expression were studied in non-high-risk (low-risk + intermediate-risk) (n = 60) and high-risk patients (n = 52) with B-precursor ALL who had been treated with the risk-directed protocol of ALL-941 trial. Although CD45 expression did not correlate with the event-free survival (EFS) of the non-high-risk patients, there was a significant correlation between the expression levels and the EFS of the high-risk patients: the 3-year EFS rate of the CD45low group (n = 26, RALV = 0.017-0.132) was 88 +/- 7% versus the CD45high group (n = 26, RALV = 0.133-0.450) at 34 +/- 24% (p < 0.05). These results show that the levels of expression of the CD45 antigen on leukemic lymphoblasts are significantly correlated with the clinical features and prognosis of childhood ALL.

Bruton tyrosine kinase gene mutations in Turkish patients with presumed X-linked agammaglobulinemia.

X-linked agammglobulinemia (XLA) is a ptototypical humoral immunodeficiency caused by mutations in the gene coding for Bruton tyrosine kinase (BTK). The genetic defect in XLA impairs early B cell development resulting in marked reduction of mature B cells in the blood. Studies from different countries have demonstrated that approximately 90% of males with presumed XLA bear mutations in BTK. In this study, we report for the first time the occurrence of BTK mutations in Turkey. We performed mutational analysis of the BTK gene in 16 Turkish male patients from 13 separate families with presumed XLA based on abnormally low peripheral blood B-cell numbers (lt; 1%), hypogammaglobulinemia, and recurrent bacterial infections. We found that in nine of the 13 families (69%) a Btk mutation caused XLA. Two of the mutations were previously described, but seven novel mutations were identified: two missense (Y39C, G584R), one nonsense (Q343X), and 4 deletions (1800-1821del, 1843-1847del, 1288-1292del, 291del) resulting in frameshift and premature stop codon. By contrast, no mutations in the BTK gene were identified in the other 4 families. A consanguinity in three of these families raises the possibility that mutations in other autosomal genes which affect early B cell development may contribute to their phenotype resembling XLA.

Characterization of mutations, including a novel regulatory defect in the first intron, in Bruton's tyrosine kinase gene from seven Korean X-linked agammaglobulinemia families.

In this report, we describe seven mutations, including a novel single base pair substitution in intron 1, of the Bruton's tyrosine kinase (Btk) gene found in 12 Korean patients with X-linked agammaglobulinemia. Various mutations, including three novel genetic alterations, were discovered using single-strand conformation polymorphism analysis and direct DNA sequencing. The effect of the intron 1 point mutation (intron 1 +5G-->A) was further evaluated using reporter constructs. Using luciferase assay experiments, we showed that the transcriptional activity of the mutant was significantly lower than in normal counterparts, indicating that the intronic mutation was functional. In addition, DNase I footprinting analysis showed that a single protected region spanning the position +3 to +15 bp hybridized with a mutant-specific probe, but not with a wild-type probe. EMSA indicated that a distinct nuclear protein has the ability to bind the mutant oligonucleotides to produce a new DNA-protein complex. We also observed decreased expression of Btk proteins in monocytes of patients having the point mutation in intron 1. Taken together with the functional analysis, our results strongly suggest the existence of a novel cis-acting element, which might be involved in the down-regulation of Btk gene transcription. Precise definition of the regulatory defect in the Btk intron 1 may provide valuable clues toward elucidating the pathogenesis of X-linked agammaglobulinemia.

SH2D1A mutations in Japanese males with severe Epstein-Barr virus--associated illnesses.

X-linked lymphoproliferative disease (XLP), a genetic disorder characterized by immunodeficiency to Epstein-Barr virus (EBV) infection, has been linked to mutations in the SH2D1A gene. To search for the occurrence of SH2D1A mutations in Japan, we performed genetic analysis of the SH2D1A gene in 40 males presenting with severe EBV-associated illnesses, including fulminant infectious mononucleosis, EBV-positive lymphoma, and severe chronic active EBV infection. SH2D1A mutations were detected in 10 of these 40 patients. Five of these 10 cases were sporadic. Patients with SH2D1A mutations displayed severe acute infectious mononucleosis with hyperimmunoglobulin M, hypogammaglobulinemia, and B-cell malignant lymphoma. By contrast, chronic active EBV infection was not associated with SH2D1A mutations. XLP survivors exhibited normal levels of circulating EBV-DNA during convalescence, suggesting that SH2D1A protein is not directly responsible for control of EBV replication. Thus, genetic analysis of the SH2D1A gene is particularly useful in the diagnosis of sporadic cases and carriers of XLP. (Blood. 2001;98:1268-1270)