Enhanced exon 2 skipping caused by c.910G>A variant and alternative splicing of MEFV genes in two independent cases of familial Mediterranean fever.

Most reported cases of familial Mediterranean fever (FMF) involve missense mutations of MEFV concentrated within exon 10. We experienced two independent pedigrees of a unique variant in the MEFV gene that might cause excessive exon 2 skipping due to enhanced alternative splicing. In this study, we tried to elucidate the molecular mechanism of the MEFV variant as a cause of the FMF phenotype. Peripheral blood was obtained from volunteers and two patients with homozygous c.910G>A variant of the MEFV gene. MEFV messenger RNA (mRNA) expression patterns in mononuclear cells and granulocytes were compared using forward and reverse primers from exons 1 and 3, respectively. Expression profiles of pyrin were examined by transfecting wild-type and variant MEFV genes into HEK293T cells. Expression of normal-sized mRNA was extremely reduced in these patients, whereas that of aberrant short mRNA, deleting exon 2 (Δex2), was significantly increased. Immunohistochemical and immunoblotting analyses revealed a truncated immunoreactive pyrin protein in cells transfected with Δex2 cDNA. The MEFV gene c.910G>A variant results in accelerated aberrant splicing with abnormal protein size, presumably leading to anomalous pyrin function. This is the first report to show that an MEFV variant other than missense mutation is responsible for the FMF phenotype.

Analysis of mutations and recombination activity in RAG-deficient patients.

Mutations in the recombination activating genes (RAG1 or RAG2) can lead to a variety of immunodeficiencies. Herein, we report 5 cases of RAG deficiency from 5 families: 3 of Omenn syndrome, 1 of severe combined immunodeficiency, and 1 of combined immunodeficiency with oligoclonal TCRγδ(+) T cells, autoimmunity and cytomegalovirus infection. The genetic defects were heterogeneous and included 6 novel RAG mutations. All missense mutations except for Met443Ile in RAG2 were located in active core regions of RAG1 or RAG2. V(D)J recombination activity of each mutant was variable, ranging from half of the wild type activity to none, however, a significant decrease in average recombination activity was demonstrated in each patient. The reduced recombination activity of Met443Ile in RAG2 may suggest a crucial role of the non-core region of RAG2 in V(D)J recombination. These findings suggest that functional evaluation together with molecular analysis contributes to our broader understanding of RAG deficiency.

Commotio Cordis presenting as a temporary complete atrioventricular block in a 2-year-old girl with congenitally corrected transposition of the great arteries.

This report describes a 2-year-old girl with congenitally corrected transposition of the great arteries (ccTGA) who presented with transient complete atrioventricular (AV) block after a mild chest blow. Running around the house with her older sister, she fell to the floor. Her sister also fell and landed on her. The girl became cyanotic and pale and experienced a transient loss of consciousness. At arrival to the emergency department, she had regained consciousness, but she remained pale. An electrocardiogram (ECG) demonstrated complete AV block with a heart rate of 78 beats per minute (bpm). The ECG after admission showed a Wenckebach-type second-degree AV block. Day 2 after admission, a 12-lead ECG showed significant ST and T-wave abnormalities in the precordial leads, but the girl had no chest pain and a normal physical examination. Echocardiography demonstrated normal contractility of the systemic right ventricle. The first-degree AV block and the ST and T-wave abnormalities on the 12-lead ECG improved gradually without abnormal Q-waves. This is the first report of ccTGA in which a transient complete AV block naturally recovered after a presentation with commotio cordis.

Clinical significance of cloned expansion and CD5 down-regulation in Epstein-Barr Virus (EBV)-infected CD8+ T lymphocytes in EBV-associated hemophagocytic lymphohistiocytosis.

Epstein-Barr virus (EBV) is the pathogen that most commonly triggers infection-associated hemophagocytic lymphohistiocytosis (HLH) and ectopically infects CD8(+) T cells in EBV-associated HLH (EBV-HLH). We recently described an EBV-HLH patient who had a clonally expanded population of EBV-infected CD8(+) T cells with CD5 down-regulation. To determine whether this finding could serve as a useful marker for EBV-HLH, we investigated 5 additional patients. We found a significant increase in the subpopulation of CD8(+) T cells with CD5 down-regulation and bright human leukocyte antigen (HLA)-DR expression in all patients with EBV-HLH but not in patients with infectious mononucleosis or in control subjects. Such T cells were frequently found to be larger cells that stained positive for a specific T cell receptor VB. We also demonstrated that those cells were the major cellular target of EBV, and their numbers progressively declined in parallel with the serum ferritin levels. All together, our findings reveal the immunophenotypic characteristics of EBV-infected CD8(+) T cells and may provide a valuable tool for the diagnosis of EBV-HLH.

Agranulocytosis after infectious mononucleosis.

We report the case of a 5-year-old boy with agranulocytosis after infectious mononucleosis (IM). Antibodies against anti-human neutrophil-specific antigens (HNA)-1 were detected in his serum. A literature review on agranulocytosis after IM and our case suggest that anti-HNA-1 antibodies play important roles in agranulocytosis associated with IM.

Clonal expansion of Epstein-Barr virus (EBV)-infected γδ T cells in patients with chronic active EBV disease and hydroa vacciniforme-like eruptions.

Chronic active Epstein-Barr virus (EBV) disease (CAEBV) is a systemic EBV-positive lymphoproliferative disorder characterized by fever, lymphadenopathy, and splenomegaly. Patients with CAEBV may present with cutaneous symptoms, including hypersensitivity to mosquito bites and hydroa vacciniforme (HV)-like eruptions. HV is a rare photodermatosis characterized by vesicles and crust formation after exposure to sunlight, with onset in childhood, and is associated with latent EBV infection. While γδ T cells have recently been demonstrated to be the major EBV-infected cell population in HV, the immunophenotypic features of EBV-infected γδ T cells in CAEBV with HV-like eruptions or HV remain largely undetermined. We describe three patients with CAEBV whose γδ T cells were found to be the major cellular target of EBV. HV-like eruptions were observed in two of these patients. A clonally expanded subpopulation of γδ T cells that were highly activated and T cell receptor Vγ9- and Vδ2-positive cells was demonstrated in all patients. We also show that the clonally expanded γδ T cells infiltrated into the HV-like eruptions in one patient from whom skin biopsy specimens were available. These results suggest the pathogenic roles of clonally expanded γδ T cells infected by EBV in patients with CAEBV and HV-like eruptions.

Flow cytometric analysis of skin blister fluid induced by mosquito bites in a patient with chronic active Epstein-Barr virus infection.

In chronic active Epstein-Barr virus (EBV) infection (CAEBV), ectopic EBV infection has been described in T or natural killer (NK) cells. NK cell-type infection (NK-CAEBV) is characterized by large granular lymphocytosis, high IgE levels and unusual reactions to mosquito bites, including severe local skin reactions, fever and liver dysfunction. However, the mechanisms underlying these reactions remain undetermined. Herein, we describe a patient with NK-CAEBV whose blister fluid after mosquito bites was analyzed. The patient exhibited significant increases in the percentage of CD56(+) NK cells in the fluid compared with a simple mosquito allergy, in which the majority of infiltrated cells were CD203c(+) cells, indicating basophils and/or mast cells. His fluid also contained CD203c(+) cells, and his circulating basophils were activated by mosquito extracts in vitro. These results suggest that CD203c(+) cells as well as NK cells may play pathogenic roles in the severe skin reactions to mosquito bites in NK-CAEBV.