Among 94 osteopetrotic patients presenting with a severe clinical picture and diagnosed early in life, 12 bore mutations in the ClCN7 gene, but only 7 of them had the expected two recessive mutations. The remaining five patients seem to be heterozygous for a ClCN7 mutation, and significant variations were observed in the clinical manifestations of their disease, even within the same family.Introduction: Human osteopetroses are a heterogeneous group of diseases that include both infantile severe, autosomal recessive (ARO) and adult autosomal dominant (ADO) forms. Two genes, Atp6a3 (TCIRG1) and ClCN7, have been shown to be associated with human ARO, the latter of which is also thought to be responsible for ADO-II. However, patients with an intermediate phenotype have been described: the genetic basis of these observances is unknown. Materials and Methods:In this study, we report the clinical and molecular analysis of 94 patients in which a diagnosis of severe osteopetrosis was made within the first 2 years of age. Both TCIRG1 and CLCN7 genes were sequenced in all patients and the molecular findings were correlated to clinical parameters. Results and Conclusions:In 56 of 94 patients with a classical picture of ARO, TCIRG1-dependent recessive mutations were found. In contrast, ClCN7 mutations were found in 12 cases (13%) of severe osteopetrosis, but only 7 of them had two recessive mutations identified: in 6 of these 7 cases, central nervous system manifestations were noted, and these patients had a poor prognosis. The remaining five cases were heterozygous for a ClCN7 mutation,

T oxoplasma gondii is a protozoan parasite distributed worldwide and infecting one-third of the global population. Infection is acquired by ingestion of parasites via consumption of undercooked meat containing tissue cysts or of water, fruits, or vegetables contaminated with oocysts. In immunocompetent individuals, primary infection results in the formation of tissue cysts and in serological evidence of infection. However, in immunocompromized patients, such as hematopoietic stem cell transplant (HSCT) recipients, toxoplasmosis is often a life-threatening opportunistic infection arising either from transmission of the parasites via a graft from a seropositive donor to a seronegative recipient or, far more frequently, from reactivation of a preexisting latent infection in a seropositive recipient, regardless of the donor's serological status (1). After allogeneic HSCT, studies have shown an incidence of invasive toxoplasmosis among seropositive recipients of 4% to 6%, with an estimated mortality rate of 60% to 90% (2, 3).Nijmegen breakage syndrome (NBS) is a rare, autosome-recessive DNA repair disorder characterized by microcephaly with normal intelligence, facial dysmorphia (bird-like facial features), primary immunodeficiency, and a predisposition to lymphoid malignancies at a young age (4, 5). Treatment of NBS-related malignancies is challenging due to the chromosomal instability and immunodeficiency which make the patients more susceptible to the toxic effects of standard chemotherapy and radiation. Although lymphoid malignancies occurring in NBS patients can be successfully brought into remission using standard chemotherapy regimens with minor dose modifications (6, 7), a high rate of treatment failure and relapse has been observed (8). An alternative treatment option for malignancies in NBS is HSCT from HLAidentical donors, which has been shown not only to correct humoral and cellular immunodeficiency but also to lower the secondary malignancy rate (9).We here present a case of an early and fulminant post-HSCT reactivation of toxoplasmosis caused by an atypical T. gondii strain in a young patient with NBS that contributed to a subsequent fatal outcome within 40 days after transplantation. This case is the first report of increased clinical severity of toxoplasmosis caused by an atypical strain in the setting of immunosuppression. It also stresses the value and necessity of the use of quantitative molecular methods to monitor T. gondii reactivation in cases of reactivation risk.(The results of this study have been presented in part at the 11th European Multicolloquium of Parasitology [EMOP XI],

BackgroundFanconi anemia (FA) is characterized by sensitivity to DNA cross-linking agents, mild cellular, and marked clinical radio sensitivity. In this study we investigated telomeric abnormalities of non-immortalized primary cells (lymphocytes and fibroblasts) derived from FA patients of the FA-D2 complementation group, which provides a more accurate physiological assessment than is possible with transformed cells or animal models.ResultsWe analyzed telomere length, telomere dysfunction-induced foci (TIFs), sister chromatid exchanges (SCE), telomere sister chromatid exchanges (T-SCE), apoptosis and expression of shelterin components TRF1 and TRF2. FANCD2 lymphocytes exhibited multiple types of telomeric abnormalities, including premature telomere shortening, increase in telomeric recombination and aberrant telomeric structures ranging from fragile to long-string extended telomeres. The baseline incidence of SCE in FANCD2 lymphocytes was reduced when compared to control, but in response to diepoxybutane (DEB) the 2-fold higher rate of SCE was observed. In contrast, control lymphocytes showed decreased SCE incidence in response to DEB treatment. FANCD2 fibroblasts revealed a high percentage of TIFs, decreased expression of TRF1 and invariable expression of TRF2. The percentage of TIFs inversely correlated with telomere length, emphasizing that telomere shortening is the major reason for the loss of telomere capping function. Upon irradiation, a significant decrease of TIFs was observed at all recovery times. Surprisingly, a considerable percentage of TIF positive cells disappeared at the same time when incidence of γ-H2AX foci was maximal. Both FANCD2 leucocytes and fibroblasts appeared to die spontaneously at higher rate than control. This trend was more evident upon irradiation; the percentage of leucocytes underwent apoptosis was 2.59- fold higher than that in control, while fibroblasts exhibited a 2- h delay before entering apoptosis.ConclusionThe results of our study showed that primary cells originating from FA-D2 patients display shorten telomeres, elevated incidence of T-SCEs and high frequency of TIFs. Disappearance of TIFs in early response to irradiation represent distinctive feature of FANCD2 cells that should be examined further.