X-linked dyskeratosis congenita presenting in adulthood with photodamaged skin and epiphora.

Dyskeratosis congenita (DC) is a clinically and genetically heterogeneous multisystem bone marrow failure disorder of telomere maintenance, which may present with dermatological features. The main cause of mortality is bone marrow failure, often developing in the second decade of life, although pulmonary disease and malignancies such as squamous cell carcinomas (SCCs) may also prove fatal. We report the case of a 28-year-old man with X-linked DC and confirmed DKC1 gene mutation. In addition to the classic triad of nail dystrophy, hyperpigmentation and oral leucoplakia, the patient had actinic keratosis (AK) and photodamaged skin, hitherto under-recognized features of this condition. Awareness of the clinical presentation of DC is important, as accurate clinical and molecular diagnosis affords patients and their families genetic counselling, cancer prevention and screening measures, and planning for complications such as bone marrow failure.

X-linked dyskeratosis congenita is caused by mutations in a highly conserved gene with putative nucleolar functions.

X-linked recessive dyskeratosis congenita (DKC) is a rare bone-marrow failure disorder linked to Xq28. Hybridization screening with 28 candidate cDNAs resulted in the detection of a 3' deletion in one DKC patient with a cDNA probe (derived from XAP101). Five different missense mutations in five unrelated patients were subsequently identified in XAP101, indicating that it is the gene responsible for X-linked DKC (DKC1). DKC1 is highly conserved across species barriers and is the orthologue of rat NAP57 and Saccharomyces cerevisiae CBF5. The peptide dyskerin contains two TruB pseudouridine (psi) synthase motifs, multiple phosphorylation sites, and a carboxy-terminal lysine-rich repeat domain. By analogy to the function of the known dyskerin orthologues, involvement in the cell cycle and nucleolar function is predicted for the protein.

Telomere length measurement can distinguish pathogenic from non-pathogenic variants in the shelterin component, TIN2.

Dyskeratosis congenita (DC) is a heterogeneous bone marrow failure syndrome with seven disease-causing genes identified to date, six of which are linked to telomere maintenance. Mutations in one of these genes (TINF2), which encodes a component of the shelterin complex, are associated with particularly short telomeres. Among the 224 consecutive patients with different forms of bone marrow failure (46 with DC, 122 with aplastic anaemia and 57 with some features of DC), we have identified 16 new families with variants in exon 6 of the TINF2 gene, eight of which are novel. We observe that the phenotype associated with these mutations extends to a severe early presentation, not always classified as DC. In addition, we see that some of the variants identified are not associated with short telomeres and are also found in asymptomatic individuals. In the absence of any direct functional assay, the data indicates that the telomere length measurement can inform us as to which variants in TINF2 are pathogenic and which may be non-pathogenic.

Reduced-intensity conditioning using fludarabine and antithymocyte globulin alone allows stable engraftment in a patient with dyskeratosis congenita.

Dyskeratosis congenita (DC) is a rare inherited disorder characterized by the triad of nail dystrophy, mucosal leukoplakia, and reticular pigmentation. Bone marrow failure is the principal cause of early mortality, and stem cell transplantation is the only cure for these patients. However, the results of conventional hematopoietic stem cell transplantation (HSCT) for patients with DC are poor because of the high incidence of transplant-related complications. We describe the successful treatment of a 21-year-old male with DC by nonmyeloablative HSCT from a matched unrelated donor. The gene responsible for the X-linked form of DC was screened and hemizygosity for the mutation Gln31Lys was found, which is consistent with the diagnosis. The conditioning regimen consisted of only fludarabine and antithymocyte globulin. Additionally, a graft-versus-host disease (GVHD) prophylaxis was administered with cyclosporine A (CSA) and mycophenolate mofetil (MMF). The regimen was well tolerated, no severe posttransplantation complications were observed, and engraftment was rapid and complete (granulocytes on day +11 and platelets on day +13). Seven months after HSCT, the patient developed GVHD of the liver after tapering CSA which was successfully treated with prednisolone, CSA, and MMF. At the time of reporting, 3 years after HSCT, the patient remained in good clinical condition with minimal signs of chronic GVHD of the oral mucosa. Thus, we conclude that a low-intensity conditioning regimen might be sufficient to induce permanent engraftment by using matched unrelated donor HSCT in DC patients and may avoid severe organ toxicity. Although allogeneic HSCT in patients with DC will not cure the underlying genetic defect it may significantly prolong survival through effective therapy for hematologic complications.

Dyskeratosis congenita: the diverse clinical presentation of mutations in the telomerase complex.

Dyskeratosis congenita is an inherited syndrome characterised by mucocutaneous features, bone marrow failure, an increased risk of malignancy and other somatic abnormalities. There is a considerable range of clinical severity and in its occult form the disease may present as idiopathic aplastic anaemia. Genes responsible for X-linked, autosomal dominant and autosomal recessive forms of the disease have been identified and been found to encode products involved in telomere maintenance. Premature shortening of telomeres could account for the pathology, affecting the tissues that turn over most rapidly. However, the protein that is mutated in the X-linked disease, dyskerin, also plays a fundamental role in ribosome biogenesis, directing the pseudouridylation of ribosomal RNA using H/ACA small nucleolar RNAs as guides. Heterozygous mutations in the RNA component of telomerase (TERC) cause the autosomal dominant form of the disease through haploinsufficiency. Disease anticipation described in these families is associated with progressive telomere shortening through the generations. Heterozygous mutations in the reverse transcriptase component of telomerase (TERT) have a more variable role, often displaying incomplete penetrance and diverse clinical presentation. The autosomal recessive form of the disease is genetically heterogeneous, although one sub-type has been described in which NOP10 is mutated. This small protein is also associated with the maturation of ribosomal RNA and the telomerase complex.

Dyskeratosis congenita: a genetic disorder of many faces.

Dyskeratosis congenita (DC) is an inherited syndrome exhibiting marked clinical and genetic heterogeneity. It is characterized by multiple features including mucocutaneous abnormalities, bone marrow failure and an increased predisposition to cancer. Three genetic subtypes are recognized: X-linked recessive DC bears mutations in DKC1, the gene encoding dyskerin, a component of H/ACA small nucleolar ribonucleoprotein particles; autosomal dominant (AD) DC has heterozygous mutations in either TERC or TERT, the RNA and enzymatic components of telomerase, respectively, and autosomal recessive DC in which the genes involved remain largely elusive. Disease pathology is believed to be a consequence of chromosome instability because of telomerase deficiency due to mutations in DKC1, TERC and TERT; in patients with DKC1 mutations, defects in ribosomal RNA modification, ribosome biogenesis, translation control or mRNA splicing may also contribute to disease pathogenesis. The involvement of telomerase complex components in X-linked and AD forms and the presence of short telomeres in DC patients suggest that DC is primarily a disease of defective telomere maintenance. Treatment is variable and complicated by the development of secondary cancers but, being a monogenic disorder, it could potentially be treated by gene therapy. DC overlaps both clinically and genetically with several other diseases including Hoyeraal-Hreidarsson syndrome, aplastic anaemia and myelodysplasia, among others and its underlying telomeric defect has implications for a broader range of biological processes including ageing and many forms of cancer.

A ribosome-related signature in peripheral blood CLL B cells is linked to reduced survival following treatment.

We have used polysome profiling coupled to microarray analysis to examine the translatome of a panel of peripheral blood (PB) B cells isolated from 34 chronic lymphocytic leukaemia (CLL) patients. We have identified a 'ribosome-related' signature in CLL patients with mRNAs encoding for ribosomal proteins and factors that modify ribosomal RNA, e.g. DKC1 (which encodes dyskerin, a pseudouridine synthase), showing reduced polysomal association and decreased expression of the corresponding proteins. Our data suggest a general impact of dyskerin dysregulation on the translational apparatus in CLL and importantly patients with low dyskerin levels have a significantly shorter period of overall survival following treatment. Thus, translational dysregulation of dyskerin could constitute a mechanism by which the CLL PB B cells acquire an aggressive phenotype and thus have a major role in oncogenesis.

Engraftment of hematopoietic progenitor cells transduced with the Fanconi anemia group C gene (FANCC).

Fanconi anemia (FA) is an autosomal recessive disorder that leads to aplastic anemia. Mutations in the FANCC gene account for 10-15% of cases. FA cells are abnormally sensitive to DNA-damaging agents such as mitomycin C (MMC). Transfection of normal FANCC into mutant cells corrects this hypersensitivity and improves their viability in vitro. Four FA patients, representing the three major FANCC mutation subgroups, were entered into a clinical trial of gene transduction aimed at correction of the hematopoietic defect. Three patients received three or four cycles of gene transfer, each consisting of one or two infusions of autologous hematopoietic progenitor cells that had been transduced ex vivo with a retroviral vector carrying the normal FANCC gene. Prior to infusion, the FANCC transgene was demonstrated in transduced CD34-enriched progenitor cells. After infusion, FANCC was also present transiently in peripheral blood (PB) and bone marrow (BM) cells. Function of the normal FANCC transgene was suggested by a marked increase in hematopoietic colonies measured by in vitro cultures, including colonies grown in the presence of MMC, after successive gene therapy cycles in all patients. Transient improvement in BM cellularity coincided with this expansion of hematopoietic progenitors. A fourth patient, who received a single infusion of transduced CD34-enriched BM cells, was given radiation therapy for a concurrent gynecologic malignancy. The FANCC transgene was detected in her PB and BM cells only after recovery from radiation-induced aplasia, suggesting that FANCC gene transduction confers a selective engraftment advantage. These experiments highlight both the potential and difficulties in applying gene therapy to FA.

Somatic mosaicism in Fanconi anemia: molecular basis and clinical significance.

Approximately 25% of patients with Fanconi anemia (FA) have evidence of spontaneously occurring mosaicism as manifest by the presence of two subpopulations of lymphocytes, one of which is hypersensitive to cross-linking agents (e.g. mitomycin C) while the other behaves normally in response to these agents. The molecular basis of this phenotypic reversion has not yet been determined. We have investigated 8 FA patients with evidence of mosaicism. Epstein-Barr virus-immortalized lymphoblastoid cell lines established from these patients exhibited an IC50 for mitomycin C of 25 to > 100 nM compared to a mean of 2 +/- 2 nM for 20 nonmosaic FA patients and 49 +/- 11 nM for 8 healthy controls. In 3 patients who were compound heterozygotes for pathogenic FAC gene mutations the molecular mechanism of the mosaicism was investigated by haplotype analysis. The results indicated that an intragenic mitotic recombination must have occurred leading to a segregation of a wild-type allele in the reverted cells and suggested two patterns of recombination. In 1 patient a single intragenic crossover between the maternally and paternally inherited mutations occurred associated with markers located distally to the FAC gene; in the other 2 patients (sibs) the mechanism appears to have been gene conversion resulting in segregants which have lost one pathogenic mutation. In 6 of the 8 patients the hematological symptoms were relatively mild despite an age range of 9-30 years.

Heterogeneous spectrum of mutations in the Fanconi anaemia group A gene.

Fanconi anaemia (FA) is a genetically heterogeneous autosomal recessive disorder associated with chromosomal fragility, bone-marrow failure, congenital abnormalities and cancer. The gene for complementation group A (FAA), which accounts for 60-65% of all cases, has been cloned, and is composed of an open reading frame of 4.3 kb, which is distributed among 43 exons. We have investigated the molecular pathology of FA by screening the FAA gene for mutations in a panel of 90 patients identified by the European FA research group, EUFAR. A highly heterogeneous spectrum of mutations was identified, with 31 different mutations being detected in 34 patients. The mutations were scattered throughout the gene, and most are likely to result in the absence of the FAA protein. A surprisingly high frequency of intragenic deletions was detected, which removed between 1 and 30 exons from the gene. Most microdeletions and insertions occurred at homopolymeric tracts or direct repeats within the coding sequence. These features have not been observed in the other FA gene which has been cloned to date (FAC) and may be indicative of a higher mutation rate in FAA. This would explain why FA group A is much more common than the other complementation groups. The heterogeneity of the mutation spectrum and the frequency of intragenic deletions present a considerable challenge for the molecular diagnosis of FA. A scan of the entire coding sequence of the FAA gene may be required to detect the causative mutations, and scanning protocols will have to include methods which will detect the deletions in compound heterozygotes.

Non-TBI stem cell transplantation protocol for Fanconi anaemia using HLA-compatible sibling and unrelated donors.

Allogeneic haemopoietic stem cell transplantation (SCT) is the only curative option for severe bone marrow (BM) failure in patients with Fanconi anaemia (FA). We have developed a non total body irradiation (TBI) conditioning protocol consisting of fludarabine (120-150 mg/m(2)), low dose of cyclophosphamide (40 mg/kg) and antilymphocyte globulin (45 mg/kg). Graft-versus-host disease (GVHD) prophylaxis was with cyclosporin alone for sibling allografts but also included Campath-1 H (days 1-5 post SCT) for the unrelated allografts. We have performed two sibling and two unrelated BM transplants with a follow-up of 11-51 months. All patients experienced minimal toxicity and were discharged from hospital 28-32 days post SCT. Neutrophil and platelet engraftment occurred from days 11 to 19 and 15 to 34, respectively. All patients achieved stable full donor haemopoiesis with normalisation of the peripheral blood count despite one of them having myelodysplasia (MDS) with 8% blasts prior to the SCT. The only site of acute GVHD was in the skin (grade I-II) and only one patient progressed to limited chronic GVHD. This protocol is associated with reduced toxicity and prompt engraftment in FA patients with AA and/or MDS undergoing SCT using sibling or unrelated donors.

Donor-derived Plasmodium vivax infection following volunteer unrelated bone marrow transplantation.

A 14-year-old girl from the UK underwent volunteer unrelated donor bone marrow transplant (VUD BMT) for accelerated phase chronic myeloid leukaemia. On day +40 she became febrile, and peripheral blood smears demonstrated a 1% Plasmodium vivax parasitaemia. Although she had never been outside the UK, her male donor had documented Plasmodium vivax infection during a vacation in Papua New Guinea. Following appropriate treatment, he had been asymptomatic for 11 months before marrow harvesting. This is the first case report of malarial transmission by VUD BMT, and illustrates the potential problem of recrudescence of latent, dormant forms of Plasmodium vivax infection following transplantation into an immuno-compromised recipient. Even after appropriate therapy, malarial infection should be included in the differential diagnosis for all post-transplant febrile episodes.

Allogeneic stem cell transplantation for Fanconi Anaemia. Severe Aplastic Anaemia Working Party of the EBMT and EUFAR. European Group for Blood and Marrow Transplantation.

Fanconi anaemia is a hereditary disorder characterised by chromosomal breaks increased by cross-linking agents. Bone marrow transplantation is the treatment of choice when a HLA identical sibling donor has been identified. The use of low-dose cyclophosphamide with thoraco-abdominal irradiation for the conditioning regimen of FA patients has lead to a dramatic improvement of survival, with a long-term survival of 75% at our institution. However, if most patients are completely cured of their haematological disease, there is concern about an increased frequency of secondary tumours, mostly head and neck squamous cell carcinomas of poor prognosis. Results of BMT using alternative donors (HLA mismatched related and unrelated donors) have also improved during the last decade. A better selection of the donor via high-resolution techniques for class-II HLA matching, and more recently the use of T cell depleted grafts are probably the main explanations. Despite a short follow-up and the small number of patients analysed, transplants using HLA matched family cord blood give some promising results. On the other hand, first results with unrelated cord blood remind that this approach is clearly an experimental one that has to be evaluated through international registries and prospective studies. New approaches including autologous stem cell transplantations and gene therapy are currently explored.

Dyskeratosis congenita is a chromosomal instability disorder.

Dyskeratosis congenita (DC) is a rare inherited disorder characterized by dystrophic changes in the skin and mucous membranes, bone marrow failure, and a predisposition to malignancy. In the majority of families the pattern of inheritance of DC has been compatible with X-linkage, the most likely location being Xq28. The primary defect responsible for this disease remains unknown. As DC shares many features (congenital abnormalities, bone marrow failure) with the chromosomal instability disorder. Fanconi's anaemia (FA), several studies have focused on cytogenetic features in DC. Unlike in FA, cytogenetic studies on peripheral blood lymphocytes have shown no significant difference between DC and normal lymphocytes with or without prior incubation with clastogens (bleomycin, diepoxybutane, mitomycin-c, 4-nitroquinoline-1-oxide). However, studies on DC fibroblasts have shown abnormalities in both morphology (polygonal cell shape, ballooning, dendritic-like projections) and growth rate (doubling time about twice normal), as well as numerous unbalanced chromosomal rearrangements (dicentrics, tricentrics, translocations) in the absence of any clastogenic agents. Bone marrow metaphases from one out of three patients studied (the eldest of the three) also showed unbalanced chromosomal rearrangements in the absence of any clastogens. Cell-specific difference and a higher rate of chromosomal rearrangements in the older patients appear to correlate with the clinical evolution of the disease. These findings suggest that the DC defect predisposes DC cells to developing chromosomal rearrangements.

Caspofungin for invasive fungal infections: combination treatment with liposomal amphotericin B in children undergoing hemopoietic stem cell transplantation.

Invasive fungal infections often prove difficult to eradicate especially in the stem cell transplant setting. Amphotericin has been the mainstay of treatment for years but has significant toxicity. Newer antifungal agents, such as caspofungin, have shown promising results in adults, particularly when used in combination with amphotericin as both drugs differ in their mode of action. However, there are few data from children and no previous published information about the use of Caspofungin after paediatric stem cell transplantation. We report our experience in children with proven invasive fungal infections after stem cell transplantation. This combination was non-toxic, and two of three patients survived their infections.

Severe aplastic anemia including Fanconi's anemia and dyskeratosis congenita.

The primary pathophysiology in the majority of cases of acquired aplastic anemia remains unknown ("idiopathic"). In contrast, there have been major advances in Fanconi's anemia, the commonest of the familial aplastic anemias. The key has been complementation analysis that provides evidence for at least five complementation groups (FA-A, FA-B, FA-C, FA-D, and FA-E) and therefore five genes for Fanconi's anemia; only the FAC gene has been cloned to date. The FAC gene has an important role in normal hematopoiesis, and expression of the mutant FAC allele is associated with increased apoptosis. Increased apoptosis is also seen in patients with idiopathic aplastic anemia. Furthermore, patients with Fanconi's anemia or dyskeratosis congenita, another familial form of aplastic anemia, have a high incidence of hematopoietic clonal disorders, as do patients with idiopathic aplastic anemia. Therefore, the familial aplastic anemias are good in vivo models for studying aplastic anemia in general; some of the idiopathic aplastic anemias could prove to be due to mutations in genes characterized originally in familial aplastic anemias. Thus identification of these genes may provide insights into the pathophysiology of idiopathic aplastic anemia and suggest new treatment options, because treatment remains unsatisfactory for patients who lack HLA-identical siblings who can serve as bone marrow donors. The recent mapping of the FA-A (16q24.3), FA-D (3p22-26), and dyskeratosis congenita (Xq28) genes suggests this goal is achievable.