SAP and XIAP deficiency in hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a multisystem inflammatory disorder due to cytokine overproduction from excessively activated lymphocytes and macrophages. HLH has been divided into two subgroups: primary HLH and secondary HLH. Primary HLH includes PRF1, UNC13D, STX11, STXBP2, RAB27A, LYST, SH2D1A and XIAP gene mutations; and secondary HLH is associated with infections, malignancies and autoimmune diseases. Among primary HLH‐related genes, SH2D1A and XIAP are genetically responsible for X‐linked lymphoproliferative syndrome (XLP) due to signaling‐lymphocytic‐activation‐molecule‐associated protein (SAP) and XIAP deficiencies, respectively. XLP is characterized by extreme vulnerability to Epstein–Barr virus infection. The major clinical manifestations of XLP consist of HLH (60%), lymphoproliferative disorder (30%) and dysgammaglobulinemia (30%). Analysis of clinical phenotypes of XLP patients suggests that XLP predominantly shows familial HLH phenotypes, whereas some XLP patients present sporadic HLH. For many decades, clinicians and investigators have been concerned with possible XLP in young boys presenting with Epstein–Barr‐virus‐associated HLH. This review aims to describe the new knowledge about XLP and to draw the attention of the pediatrician to XLP, which should be differentiated from other forms of HLH.     

Novel mutations in SH3TC2 in a young Japanese girl with Charcot‐Marie‐Tooth disease type 4C

Charcot‐Marie‐Tooth disease type 4C (CMT4C) is an autosomal recessive demyelinating form of CMT characterized clinically by early onset and severe spinal deformities, and is caused by mutations in SH3TC2. We describe the case of a 10‐year‐old Japanese girl diagnosed with CMT4C. The patient developed progressive foot deformities such as marked pes cavus and ankle contracture, with mild muscle weakness in both legs, and generalized areflexia. On electrophysiological studies, motor nerve conduction velocity ranged from 22.3 m/s in the tibial nerve to 48.2 m/s in the median nerve. Sensory nerve conduction velocity ranged from 30.3 m/s in the sural nerve to 52.8 m/s in the median nerve. Sequence analysis of candidate genes identified two novel heterozygous mutations, c.229C>T and c.2775G>A, in SH3TC2. The patient was diagnosed as having CMT4C with novel mutations, making this the first documented Japanese pediatric case.     

Novel SCN1A mutations in Indonesian patients with severe myoclonic epilepsy in infancy

Background: Severe myoclonic epilepsy in infancy (SMEI) and borderline SMEI (SMEB) are caused by a mutation in SCN1A, which encodes a voltage‐gated sodium channel α1‐subunit protein. Although many mutations in SCN1A have been associated with clinical features of SMEI or SMEB from different ethnic groups, there have been no such reports from the South‐East Asian populations so far. Methods: Patients 1 and 2 were Indonesian children diagnosed as having SMEI and SMEB based on their clinical features. SCN1A was screened for mutations using a combination of polymerase chain reaction and denaturing high‐performance liquid chromatography. Nucleotide substitutions were confirmed on direct sequencing. Results: In patient 1, a G‐to‐A heterozygous transition was detected at nucleotide 4834 (c.4834G>A) in exon 25, leading to substitution of valine with isoleucine at amino acid position 1612 (p.V1612I) in the SCN1A protein. In patient 2 a T‐to‐G heterozygous transversion was identified at nucleotide 5266 (c.5266T>G) in exon 26, leading to substitution of cysteine with glycine at amino acid 1756 (p.C1756G) in the SCN1A protein. Both amino acid substitutions might disrupt these highly conserved regions in species from drosophila to human, leading to dysfunction of the protein. p.V1612I and p.C1756G were determined as disease‐causing mutations due to their absence in the control population. Conclusion: The first cases of SMEI and SMEB are reported in South‐East Asian populations. Two novel SCN1A mutations are also identified in these patients, p.V1612I and p.C1756G, which may lead to neuronal excitability or convulsions.     

The carriage of the type 1 diabetes‐associated R262W variant of human LNK correlates with increased proliferation of peripheral blood monocytes in diabetic patients

Lavrikova EY, Nikitin AG, Kuraeva TL, Peterkova VA, Tsitlidze NM, Chistiakov DA, Nosikov VV. The carriage of the type 1 diabetes‐associated R262W variant of human LNK correlates with increased proliferation of peripheral blood monocytes in diabetic patients. Objective: Lymphocyte adaptor protein (LNK) plays a pivotal role as a suppressor of T‐cell receptor‐mediated immune signaling and negative regulator of lymphopoiesis and early hematopoiesis. Recently, association between the R262W (c.784T>C) variant of the SH2B3 gene (rs3184504) encoding human LNK and type 1 diabetes (T1D) was found in several populations. In this study, we aimed to check whether this marker is associated with T1D in a Russian population. Methods: Using a Taqman allele discrimination assay, we genotyped 1062 unrelated Russian individuals with diabetes at childhood and adolescence onset and 1020 healthy controls. T‐cell proliferation assay based on the measurement of incorporation of bromo‐2′‐deoxyuridine incorporation into newly synthesized DNA was used to evaluate whether carriage of SH2B3 784T>C correlates with T‐cell proliferation in patients' peripheral mononuclear blood cells (PMBCs) stimulated with anti‐CD28 and anti‐CD3 antibodies. Results: The allele 784C of SH2B3 was related to a higher risk of T1D (odds ratio of 1.52, p = 1.2 × 10^?12). A correlation between the carriage of the predisposing C/C variant of LNK and increased proliferation of T lymphocytes was shown in PMBCs of both diabetic [C/C vs. C/T vs.T/T = optical density at 450 nm (OD₄₅₀) 6.3 ± 0.8 vs. 4.4 ± 0.7 vs. 2.7 ± 0.5, p = 0.0007] and non‐diabetic (C/C vs. C/T vs.T/T = OD₄₅₀2.9 ± 0.6 vs. 2.2 ± 0.4 vs. 1.7 ± 0.4, p = 0.022) patients. Conclusions: The SH2B3 784T>C variant could contribute to the pathogenesis of T1D through impaired immune response that promotes activation and expansion of self‐reactive lymphocytes in susceptible individuals.     

X-连锁淋巴细胞异常增生症一例及其家系基因和蛋白表达研究

目的 探讨1例中国X-连锁淋巴细胞异常增生症(XLP)患儿及其家系的临床特征、基因突变和外周血单个核细胞(PBMC)SAP蛋白表达.方法 患儿男,6岁,于5岁时发现右腰部肿物,活检提示为伯基特淋巴瘤.其胞兄及表兄均于1岁左右因重症传染性单核细胞增多症夭折.据临床表现、家族史、免疫学特征拟诊为XLP.提取患儿及部分亲属基因组DNA,采用PCR法扩增SH2D1A基因,PCR产物直接进行双向序列测定,采用流式细胞仪检测PBMC中SAP蛋白表达.结果 患儿在缓解期EBV-DNA检测为536.9拷贝/ml(＞500拷贝/ml为EBV阳性),其SH2D1A基因第2外显子462位核苷酸发生无义突变,碱基C突变为T,形成TGA终止密码子(Arg55X),患儿母亲、姨母及外祖母为该突变携带者.患儿PBMC中SAP蛋白表达水平明显下降,而携带者SAP蛋白表达未见异常.结论 通过临床及实验室检查,确诊1例XLP患儿及家系.男性重症EBV感染,甚或无EB病毒感染证据,但具有家族史的淋巴瘤患儿应考虑XLP.SAP蛋白流式细胞仪检测为快速、准确的诊断手段.

Abstract：

Objective X-linked lymphopmliferative disease(XLP),a genetic disorder characterized by immunodeficiency to Epstein-Barr virus(EBV)infection,has been linked to mutations in the SH2D1 A gene.XLP patient displays EBV associated fulminant infectious mononucleosis or hemophagocytie lymphohistocytosis,hypogammaglobulinemia or malignant lymphoma.Here we report the clinical features.gene mutation and SAP expression on PBMCs of a Chinese patient with XLP and potential carriers.Method A 6 years old male patient and his maternal relatives were enrolled in this study.The patient was found to have with a renal Burkitt lymphoma on the right waist at 5 years of age by accident.His elder brother and a maternally related cousin botIl died of multiple systemic organ dysfunction syndrome (MODS)due to fulminant infectious mononucleosis(FIM)at the age of one year.The patient and his maternal relatives were subjected to detection of SAP expression on the PBMCs by flow cytometry and gene mutation analysis of SH2D1A by using PCR based on genomic DNA.Result The patient exhibited 536.9copy/ml level of circulating EBV-DNA during remission.Sequence analysis showed that the patient harbored a nonsense mutation in exon 2(C462T),resulting in a premature stop codon(Arg55X).His mother and some of the matemal relatives were proved to be carriers of this mutation.SAP expression from the patient was significantly reduced as compared to normal individual and the carriers.Conclusion We identified a Chinese XLP ease genetically.Assessment of SAP expression on PBMCs by flow cytometry seemed to be an effective rapid diagnostic method for this disease.Absence of EBV infeetion does not diminish the possibility of XLP.     

X-连锁淋巴细胞异常增生症一例及其家系基因和蛋白表达研究

目的 探讨1例中国X-连锁淋巴细胞异常增生症(XLP)患儿及其家系的临床特征、基因突变和外周血单个核细胞(PBMC)SAP蛋白表达.方法 患儿男,6岁,于5岁时发现右腰部肿物,活检提示为伯基特淋巴瘤.其胞兄及表兄均于1岁左右因重症传染性单核细胞增多症夭折.据临床表现、家族史、免疫学特征拟诊为XLP.提取患儿及部分亲属基因组DNA,采用PCR法扩增SH2D1A基因,PCR产物直接进行双向序列测定,采用流式细胞仪检测PBMC中SAP蛋白表达.结果 患儿在缓解期EBV-DNA检测为536.9拷贝/ml(＞500拷贝/ml为EBV阳性),其SH2D1A基因第2外显子462位核苷酸发生无义突变,碱基C突变为T,形成TGA终止密码子(Arg55X),患儿母亲、姨母及外祖母为该突变携带者.患儿PBMC中SAP蛋白表达水平明显下降,而携带者SAP蛋白表达未见异常.结论 通过临床及实验室检查,确诊1例XLP患儿及家系.男性重症EBV感染,甚或无EB病毒感染证据,但具有家族史的淋巴瘤患儿应考虑XLP.SAP蛋白流式细胞仪检测为快速、准确的诊断手段.     

Fibrinogen Columbus II: A novel c.1075G>T mutation in the FGG gene causing hypodysfibrinogenemia and thrombosis in an adolescent male

Hypodysfibrinogenemia, the least frequently reported congenital fibrinogen disorder is characterized by low circulating levels of a dysfunctional protein, and is associated with phenotypic features of both hypo‐ and dysfibrinogenemia. Herein, we report an adolescent male with unprovoked venous thromboembolism and hypodysfibrinogenemia. Patient had recurrent, progressive thrombosis despite therapeutic anticoagulation with both low molecular weight heparin and warfarin. He had clinical and radiological improvement after transition to a direct thrombin inhibitor. Sequencing of the FGG gene identified a novel heterozygous mutation, c.1075G>T. Structural visualization of the identified variant was pursued and suggested that the mutation likely destabilizes the Ca²⁺‐binding site of fibrinogen resulting in pathogenicity.     

A novel INS mutation in a family with maturity‐onset diabetes of the young: Variable insulin secretion and putative mechanisms

Insulin gene (INS) mutations cause a rare form of maturity‐onset diabetes of the young (MODY), a heterogeneous group of autosomal dominant diabetes with at least 14 confirmed causative genes. Here, we describe a family with MODY due to a novel INS mutation, detected using massively parallel sequencing (MPS). The proband presented aged 11 years with mild diabetic ketoacidosis. She was negative for IA2 and GAD antibodies. She had a strong family history of diabetes affecting both her two siblings and her mother, none of whom had ketosis but who were considered to have type 1 diabetes and managed on insulin, and her maternal grandfather, who was managed for decades on sulfonylureas. Of note, her younger sister had insulin deficiency but an elevated fasting proinsulin:insulin ratio of 76% (ref 5%‐30%). Sanger sequencing of HNF4A, HNF1A, and HNF1B in the proband was negative. Targeted MPS using a custom‐designed amplicon panel sequenced on an Illumina MiSeq detected a heterozygous INS mutation c.277G>A (p.Glu93Lys). Sanger sequencing confirmed the variant segregated with diabetes within the family. Structural analysis of this variant suggested disruption of a critical hydrogen bond between insulin and the insulin receptor; however, the clinical picture in some individuals also suggested abnormal insulin processing and insulin deficiency. This family has a novel INS mutation and demonstrated variable insulin deficiency. MPS represents an efficient method of MODY diagnosis in families with rarer gene mutations.     

Two Novel Missense Mutations and a 5bp Deletion in the Erythroid‐Specific Promoter of the PKLR Gene in Two Unrelated Patients With Pyruvate Kinase Deficient Transfusion‐Dependent Chronic Nonspherocytic Hemolytic Anemia

We report two children with severe chronic hemolytic anemia, the cause of which was difficult to establish because of transfusion dependency. Reduced erythrocyte pyruvate kinase activity in their asymptomatic parents provided the diagnostic clues for mutation screening of the PKLR gene and revealed that one child was a compound heterozygote of a novel paternally derived 5‐bp deletion in the promoter region (c.‐88_‐84delTCTCT) and a maternally derived missense mutation in exon nine (c.1174G>A; p.Ala392Thr). The second child was a compound heterozygote of two novel missense mutations, namely a paternally derived exon ten c.1381G>A (p.Glu461Lys) and a maternally derived exon seven c.907‐908delCC (p.Pro303GlyfsX12) variant.     

Deficiency of ADA2 mimicking autoimmune lymphoproliferative syndrome in the absence of livedo reticularis and vasculitis

Adenosine deaminase‐2 (ADA2) deficiency (DADA2) is associated with early onset polyarteritis nodosa and vasculopathy. Classic presentation includes livedo reticularis, vasculitis, and stroke. However, the phenotype and disease severity are variable. We present a 5‐year‐old female who presented with features that mimicked autoimmune lymphoproliferative syndrome (ALPS) in the absence of classic features of DADA2. Exome sequencing identified a novel homozygous splicing variant in ADA2 c.882‐2A > G. Patient responded to anti‐ tumor necrosis factor medication and is in complete remission. Hematologists should be aware of various hematological presentations of DADA2, including ALPS‐like disorder, that might lack vasculitis and livedo reticularis to prevent delay in initiating optimal therapy.     

Novel splice‐site mutation in WDR62 revealed by whole‐exome sequencing in a Sudanese family with primary microcephaly

The WDR62 gene encodes a scaffold protein of the c‐Jun N‐terminal kinase (JNK) pathway. It plays a critical role in laying out various cellular layers in the cerebral cortex during embryogenesis, and hence the dramatic clinical features resulting from WDR62 mutations. These mutations are associated with autosomal recessive primary microcephaly 2, with or without cortical malformations (MCPH2). Using whole exome sequencing we uncovered a novel WDR62 variant; c.390G > A, from two Sudanese siblings whose parents are first cousins. The patients suffered MCPH2 with incomplete lissencephaly and developmental delay. The mutation affects the last nucleotide of exon4, and probably leads to aberrant splicing, which may result in a truncated protein lacking all functional domains.     

Allogeneic hematopoietic stem cell transplantation is associated with cure and durable remission of late‐onset primary isolated central nervous system hemophagocytic lymphohistiocytosis

Primary isolated CNS presentation of HLH is exceedingly rare and typically associated with significant morbidity and mortality. We describe an adolescent patient with late‐onset, primary isolated CNS HLH and a compound heterozygous PRF1 mutation (c50delT (p.L17 fs); c.1229G>C (p.R410P)), not previously reported with this phenotype. He was successfully treated with allogeneic HSCT following a reduced‐intensity conditioning regimen, despite a high pre‐HSCT comorbidity index. Two years after transplant, he is alive and in disease remission. While patients with systemic HLH and active CNS disease have relatively poorer outcomes, a high index of suspicion may aid with early diagnosis of primary isolated CNS HLH; prompt treatment with HSCT may be associated with improved cure and durable remission of this rare disease.     

Novel STXBP2 Mutation Causing Familial Hemophagocytic Lymphohistiocytosis

Familial Hemophagocytic Lymphohistiocytosis (FHL) is a rare autosomal recessive disorder. Diagnosis is established in presence of genetic mutation or positive family history in one of the siblings. Common genetic mutations associated with FHL are mutations in gene PRF-1 (also known as FHL 2), UNC13D (FHL 3) and STX11 (FHL 4). Recently mutation in STXBP2 encoding syntaxin binding protein 2 (Munc 18 -2) has been found to be associated with FHL type 5. Here we describe the first reported Indian patient with homozygous mutation in STX BP2 gene (c1697 G>A resulting in amino acid change p.G566D) causing FHL 5.     

Donor‐specific anti‐HLA antibody production following pediatric ABO‐incompatible heart transplantation

ABO‐i heart transplantation can be performed in infants with end‐stage heart failure to increase organ availability. The development of newly detected DSAs is associated with decreased cardiac graft survival, and the effect of ABO‐i transplantation on DSA production is unknown. We examined DSA production and rejection frequency in infant recipients of ABO‐i and ABO‐c heart transplants via a retrospective cohort study of infant heart transplant recipients transplanted at a single pediatric center between January 2004 and November 2014. Patients were included if they were less than 1 year of age at transplant and had a minimum of 6 months follow‐up. DSA positivity was examined under two categories, either the lowest level detectable (MFI > 500) or a level presumed to have clinical relevance in our immunogenetics laboratory (MFI > 5000). Of 52 patients, 36 received ABO‐c transplants and 16 received ABO‐i transplants. Compared to ABO‐c recipients, the ABO‐i group showed a consistent but statistically non‐significant finding of less frequent ndDSA positivity (69.4% ABO‐c vs 43.8% ABO‐i with MFI >500, P = 0.122; 41.7% ABO‐c vs 25% ABO‐i with MFI >5000, P = 0.353). Additionally, ABO‐i patients were less likely to have any form of rejection (12.5% vs 47.2%, P = 0.027) or acute cellular rejection (6.3% vs 38.9%, P = 0.021). Our data suggest that infants receiving ABO‐i heart transplants may be less likely to develop ndDSAs or have rejection compared to same age ABO‐c recipients. Larger multicenter studies are needed to confirm results from this single center study.     

Rare coincidence of familial central core disease and hemophagocytic lymphohistiocytosis

Central core disease is a congenital myopathy caused by mutations in RYR1. A 6‐year‐old girl was admitted due to difficulty in running and climbing stairs. Another 13 members through the four generations had similar symptoms, indicating autosomal dominant inheritance. Muscle biopsy showed the characteristic central cores in predominant type 1 fibers. She later developed hemophagocytic lymphohistiocytosis. Mutation analysis identified c.14582G>A in RYR1, and c.1693delG and c.2954 + 5G>A in UNC13D. To our knowledge, this is the first case of a patient with central core disease, carrying a RYR1 mutation in a Korean large family, who had concurrent familial hemophagocytic lymphohistiocytosis.     

Differing phenotypes of Moyamoya disease in a familial case involving heterozygous c.14429G > A variant in RNF213

Moyamoya disease (MMD) is a chronic steno‐occlusive arteriopathy involving the development of abnormal collateral vessels. Ring finger protein (RNF213) on the 17q25.3 locus was identified as an MMD‐susceptibility gene in East Asian populations. We report a 5‐year‐old Japanese boy diagnosed with cerebral infarction and unilateral MMD. Magnetic resonance angiography (MRA) showed severe stenosis of the left internal carotid artery (ICA), terminal portion of the left ICA, and left origin of the posterior cerebral artery. Genetic testing indicated a heterozygous c.14429G > A (formerly described as c.14576G > A) variant in RNF213. The boy's mother had no neurological symptoms, but sequencing of RNF213 showed the same variant, and MRA indicated stenosis of the terminal bilateral ICA. This is the first report, to our knowledge, of different MMD phenotypes in a familial case involving the same heterozygous c.14429G > A variant in RNF213. Genetic testing for RNF213 is suggested for family member screening.     

Paramyotonia congenita: From clinical diagnosis to in silico protein modeling analysis

Background: Paramyotonia congenita (PMC) is an autosomal dominant disorder characterized by cold‐ or exercise‐induced myotonia. PMC is caused by a mutation in SCN4A which encodes the α‐subunit of the skeletal muscle sodium channel. Methods: The patient was an 11‐year‐old Japanese girl who was diagnosed as having PMC. To confirm the diagnosis, an orbital ice‐pack test and blinking tests were performed. Next, to identify the mutation, genetic analysis of SCN4A was performed. Finally, to evaluate the mutation effect on the protein structure, in silico protein modeling analysis was performed. Results: Cold‐ and exercise‐induced myotonia was reproduced in the patient with non‐invasive bedside tests: ice‐pack and blinking tests. In the genetic analysis, a missense mutation, c.4343G>A in SCN4A, was identified, which may result in an arginine to histidine substitution at 1448 in the protein sequence (p.Arg1448His). According to the protein modeling analysis, the mutation neutralized the positive electrostatic charge at 1448 in the DIV/S4 segment and disrupted the beginning of the helical structure in the DIV/S3‐S4 linker of the SCN4A protein. Conclusions: Diagnostic physical interventions in the patient confirmed the phenotype presentation consistent with PMC, and the in silico protein modeling analysis of p.Arg1448His predicted structural changes which can affect function of the protein. All the data confirmed the diagnosis of PMC in the patient and added to existing literature emphasizing the important role of arginine residue at 1448.     

Congenital nephrotic syndrome with a novel NPHS1 mutation

Congenital nephrotic syndrome of the Finnish type (CNF) is a rare autosomal recessive disorder. The incidence of CNF is relatively high in Finland but considerably lower in other countries. We encountered a male newborn with CNF, associated with compound heterozygous mutations in nephrosis 1, congenital, Finnish type (NPHS1). The patient was admitted to hospital as a preterm infant. Physical and laboratory findings fulfilled the diagnostic criteria of nephrotic syndrome, and were compatible with a diagnosis of CNF, but there was no family history of the disease. On genetic analysis of NPHS1 a paternally derived heterozygous frame‐shift mutation caused by an 8 bp deletion, resulting in a stop codon in exon 16 (c.2156‐2163 delTGCACTGC causing p.L719DfsX4), and a novel, maternally derived nonsense mutation in exon 15 (c.1978G>T causing p.E660X) were identified. Early genetic diagnosis of CNF is important for proper clinical management and appropriate genetic counseling.