Constitutional Bone Marrow Failure Research Articles

Early Onset Colorectal Cancer: An Emerging Cancer Risk in Patients with Diamond Blackfan Anemia.

Diamond Blackfan anemia (DBA) is a rare inherited bone marrow failure syndrome, the founding member of a class of disorders known as ribosomopathies. Most cases result from loss of function mutations or deletions in 1 of 23 genes encoding either a small or large subunit-associated ribosomal protein (RP), resulting in RP haploinsufficiency. DBA is characterized by red cell hypoplasia or aplasia, poor linear growth and congenital anomalies. Small case series and case reports demonstrate DBA to be a cancer predisposition syndrome. Recent analyses from the Diamond Blackfan Anemia Registry of North America (DBAR) have quantified the cancer risk in DBA. These studies reveal the most prevalent solid tumor, presenting in young adults and in children and adolescents, to be colorectal cancer (CRC) and osteogenic sarcoma, respectively. Of concern is that these cancers are typically detected at an advanced stage in patients who, because of their constitutional bone marrow failure, may not tolerate full-dose chemotherapy. Thus, the inability to provide optimal therapy contributes to poor outcomes. CRC screening in individuals over the age of 50 years, and now 45 years, has led to early detection and significant improvements in outcomes for non-DBA patients with CRC. These screening and surveillance strategies have been adapted to detect familial early onset CRC. With the recognition of DBA as a moderately penetrant cancer risk syndrome a rational screening and surveillance strategy will be implemented. The downstream molecular events, resulting from RP haploinsufficiency and leading to cancer, are the subject of significant scientific inquiry.

Novel V1551L Mutation in SAMD9L Inhibits Cell Cycle Progression and Results in Pancytopenia That Progresses to MDS with Monosomy 7

Germline SAMD9L mutation is a recently recognized cause of constitutional bone marrow failure with a unique propensity for clonal evolution to myelodysplastic syndrome (MDS) with monosomy 7. It is now known that a clinical syndrome originally described in the 1970s as Ataxia-Pancytopenia Syndrome is caused by missense mutation in SAMD9L, and subsequent case series have demonstrated diverse clinical outcomes in patients with germline SAMD9L mutations. SAMD9L is located on chromosome 7, and gain-of-function mutations in SAMD9L is thought to decrease cell proliferation by inhibiting the normal cell cycle. In patients with SAMD9L mutations, the development of a monosomy 7 clone then rescues the inhibitory effect of mutant SAMD9L but can result in progression to acute leukemia. Interestingly, there are also reports of transient monosomy 7 due to uniparental disomy occurring in the monosomy 7 clone resulting in normal hematopoiesis.We describe the case of a male patient who presented at age 8-months of age with fever, hypotension, and pancytopenia. Bone marrow biopsy was hypocellular with debris-laden histiocytes. Diagnostic evaluation included normal chromosome stability testing (DEB and MMC), normal telomere length testing, and normal gene panels for inherited bone marrow failure and primary HLH. Patient, then, had spontaneous count recovery on day 41 of illness with progressive improvement becoming transfusion independent without any further infections. Repeat bone marrow biopsy 1 month after count recovery demonstrated dysplasia and cytogenetic evaluation revealed monosomy 7 in 11 out of 20 metaphases. Whole exome sequencing demonstrated a novel mutation in SAMD9L. Parents were analyzed for the SAMD9L mutation which were negative. Repeat bone marrow evaluation at 4, 7, and 10 months after presentation continued to demonstrate dysplasia and monosomy 7. After 12 months of observation, decision was made to perform a bone marrow transplant but the patient died from diffuse alveolar hemorrhage shortly after engraftment.EdU incorporation assay showed that 293T cells expressing SAMD9L V1551L mutation exhibit a cell cycle arrest phenotype as shown by the lack of cells in S phase compared to cells expressing the normal SAMD9L protein or empty vector. Furthermore, Digital droplet PCR (ddPCR) with wild type- and mutation-specific primers was used to quantify the percent of mutant allele in the patients' fibroblasts, whole blood, granulocytes, lymphocytes and lymphocyte cell cultures over 12 weeks. The patient's whole blood DNA had a low fraction of the mutation (26.8%), supporting the cytogenetic finding of mosaic monosomy 7. Interestingly, lymphocyte cell line generated from the patient's blood showed a higher fraction of mutation in about 40-45% similar to what is seen in fibroblasts which suggests that the patient's monosomy 7 clone which rescued the neutrophil count seems to preferentially contribute to the myeloid lineage versus the lymphocyte lineage. We have further developed induced pluripotent stem cells from this patient to further explore this question.In summary, our case describes a novel SAMD9L heterozygous missense mutation (p.Val1551Leu) resulting in gain-of-function mutation which inhibits cellular proliferation resulting in bone marrow failure. This case highlights the new insights offered through the use of whole exome sequencing and also the difficulty of making the clinical decision to treat with bone marrow transplant in the setting of multiple reports of disease remission via self-correction. If we are able to identify the clone giving rise to mature cells and quantify it over time, we may be able to provide a more informed recommendation regarding bone marrow transplant versus observation. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Heterozygous RTEL1 variants in bone marrow failure and myeloid neoplasms

AbstractBiallelic germline mutations in RTEL1 (regulator of telomere elongation helicase 1) result in pathologic telomere erosion and cause dyskeratosis congenita. However, the role of RTEL1 mutations in other bone marrow failure (BMF) syndromes and myeloid neoplasms, and the contribution of monoallelic RTEL1 mutations to disease development are not well defined. We screened 516 patients for germline mutations in telomere-associated genes by next-generation sequencing in 2 independent cohorts; one constituting unselected patients with idiopathic BMF, unexplained cytopenia, or myeloid neoplasms (n = 457) and a second cohort comprising selected patients on the basis of the suspicion of constitutional/familial BMF (n = 59). Twenty-three RTEL1 variants were identified in 27 unrelated patients from both cohorts: 7 variants were likely pathogenic, 13 were of uncertain significance, and 3 were likely benign. Likely pathogenic RTEL1 variants were identified in 9 unrelated patients (7 heterozygous and 2 biallelic). Most patients were suspected to have constitutional BMF, which included aplastic anemia (AA), unexplained cytopenia, hypoplastic myelodysplastic syndrome, and macrocytosis with hypocellular bone marrow. In the other 18 patients, RTEL1 variants were likely benign or of uncertain significance. Telomeres were short in 21 patients (78%), and 3′ telomeric overhangs were significantly eroded in 4. In summary, heterozygous RTEL1 variants were associated with marrow failure, and telomere length measurement alone may not identify patients with telomere dysfunction carrying RTEL1 variants. Pathogenicity assessment of heterozygous RTEL1 variants relied on a combination of clinical, computational, and functional data required to avoid misinterpretation of common variants.

Heterozygous RTEL1 Variants Are Associated with Bone Marrow Failure and Abnormal Clinical Phenotype

IntroductionHeterozygous RTEL1 mutations have recently been described in familial pulmonary fibrosis (PF) but are not known to be associated with cytopenias or bone marrow failure (BMF), in contrast to heterozygous mutations in other telomere maintenance genes TERT, TERC and TINF2. Constitutional BMF syndromes typically present with less severe pancytopenia and it is often unclear if they have hypocellular MDS (hypoMDS) or non-severe AA (NSAA) morphologically.MethodsWe screened 284 patients with idiopathic AA or uncharacterised BMF and 172 patients with MDS or acute myeloid leukemia (AML) for TL and RTEL1 variants, and for the other currently known telomere gene complex (TGC) mutations, after excluding patients with Fanconi anemia, DBA or other known inherited BMF syndrome. TL was measured using a monochrome multiplex quantitative PCR method on peripheral blood mononuclear cells. Illumina Nextera-amplicon sequencing was used to screen exons of the DC genes (DKC1, TERC, TERT, RTEL1, CTC1, NHP10, NOP2, USB1, WRAP53, TINF2, PARN and ACD) by MiSeq platform. Constitutional DNA was also analysed in 10 patients (skin 9, buccal swab 1) with RTEL1 variants. A targeted gene panel of 24 genes of an Illumina Tru-Seq Custom Amplicon workflow and platform was used to identify genes frequently mutated in MDS/AML. Impact of mutations was predicted based on 3D structure information from comparative modelling for the helicase domain, comprising the HD1 and HD2 subdomains, a Fe-S cluster and an ARCH domain, and for two harmonin-like (HML) domains and a RING finger domain, located in the C-terminal regulatory region of RTEL1.ResultsHeterozygous RTEL1 variants were identified in 20 (4.4%) patients. RTEL1 variant allele frequency (VAF) was 45-70% consistent with heterozygous inheritance in all cases. TL was short in 18 (90%) patients, being < 1st centile in 15 and <10th centile in 3. 2 patients had normal TL, <20th centile and >50th centile, respectively. Median age was 35 years (range 18-73). 15/20 (75%) had a hypocellular BM (7 hypoMDS, 5 non-severe AA, 3 ICUS), and 1 each with RAEB1, RAEB2, CMML1, AML and isolated macrocytosis. 3 patients had abnormal karyotype: +8 (hypoMDS), -Y,+1,del(1) (hypoMDS), del7q (RAEB1). 2 other patients with hypoMDS had somatic mutations: U2AF1 (30% VAF) with ASXL1 (27% VAF); U2AF1 (43% VAF). Lung abnormalities were early PF (1), interstitial lung disease (1), and abnormal lung function with reduced TLCO (1) and an obstructive picture (1). Liver fibrosis with portal hypertension and varices and reticulate skin pigmentation were present in the patient with ILD, 2 patients had dystrophic nails, and 1 unexplained mild hepato-splenomegaly. 2 patients had familial MDS, 5 had a family history of cancers affecting first-degree relatives, and 2 had skeletal and cartilage anomalies, associated with learning difficulties in 1 patient. 8/15 patients with hypocellular BM required no treatment (5 hypoMDS and 3 NSAA), one hypoMDS had CR with ciclosporin and another underwent successful unrelated donor stem cell transplant; for NSAA, 2 received ATG with CSA, with PR followed by relapse in one, the other was lost to follow up, and 1 was androgen responsive. 16/20 (80%) patients are alive; 3 patients with RAEB or AML died of progressive disease and 1 patient with ICUS and severe constitutional features died from lymphoma 10 years after presentation.Mutations were spread throughout the entire RTEL1 sequence (summarised in Figure). 3D structure analysis predicted the missense RTEL1 mutations would result in disturbance of the FeS cluster and/or interfere with DNA binding, destabilisation of the HD1, HD2 or the ARCH sub-domains of the helicase domain, or destabilisation of inter-domain interactions. One HML1 mutation occurred in a loop opposite the putative ligand binding site and the rest in the variable regions outside the conserved domains. RTEL1 variants were associated with TERT mutations in 4 patients, of which 3 were known pathogenetic and 1 novel TERT mutation with low telomerase activity on TRAP assay confirming its pathogenetic nature.ConclusionsWe show for the first time that heterozygous RTEL1 mutations occur in 4.4% of patients, most commonly in young patients with a hypocellular BM, and often a family history of BMF/malignancy, and less often with high risk MDS/AML. Abnormal clinical features were present in a third of patients, some similar to but others distinct from dyskeratosis congenita. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

A Comparison of Resource Utilization, Cost and Mortality in Children Treated for Severe Aplastic Anemia

BACKGROUNDSevere Aplastic Anemia (SAA) in childhood is fatal if untreated and has a reported incidence of 2.34/ million. With the use of treatment guidelines, outcomes have improved over the years. In the United States (US), Hematopoietic Stem Cell Transplantation (HSCT) is preferentially utilized in young patients with an HLA matched sibling donor, whereas Immunosuppressive Therapy (IST) comprised of Horse Antithymocyte Globulin (ATG) and Cyclosporine (CSA) is utilized in those that lack one. Upon failure of IST, the latter typically undergo unrelated donor HSCT. At this time, national trends in resource utilization and the financial impact of this diagnosis and its treatment are unknown. Our objective was to ascertain whether treatment paradigms could be identified within a national database and compare cost and outcomes within Childrens hospitals across the US within the context of SAA. METHODSWe utilized the Pediatric Hospital Information System (PHIS) database to perform a retrospective cohort study of patients admitted to Childrens Hospital Association Hospitals (36 of 48 were free-standing) to compare length of stay (LOS), billed charges and inpatient mortality in patients with SAA who received IST compared to SCT. This database was queried to identify all patients ≤21 years of age who were first admitted between 2010 to 2014 with a diagnosis of SAA, as defined by ICD 9 codes (284. 0, 284.1, 284.9, 284.89, 284.12). Within this data set we identified patients with a Bone Marrow Aspiration (BMA) procedure code (41.3, 41.31) billed within 6 months of the code for SAA and use of transplant procedure codes (41.0, 41.00, 41.02, 41.03, 41.05, 06, and 08) drug codes for agents typically utilized as IST (164130, 164131, and 167115) or conditioning for HSCT (171103, 171125, 164130, and 164131). Patients were excluded for constitutional bone marrow failure, cancer and other diagnoses. Those meeting criteria were summarized using descriptive statistics and comparisons among groups were assessed using non-parametric methods. Cost, number of admissions, LOS, intensive care unit (ICU) utilization, inpatient mortality and comorbidities were analyzed with various charge codes that were adjusted by the CMS wage/price index for the hospital’s location. The data set was validated by internal chart review. RESULTSA total of 446 patients (57% male, 43% female, median age at diagnosis 10 years) met study criteria. 282(63%) patients were treated with IST alone, 98(22.3%) patients who underwent SCT without IST and 66(14.7%) patients received both forms of therapy. The overall mortality rate for the cohort was 8.6%. The likelihood of death correlated with the presence of Graft versus Host Disease (GVHD) and LOS > 100 days in the group that underwent SCT.A total of 1631 admissions were evaluated with a total LOS of 24,369 days. Median LOS for the cohort was 36 days but significantly lower for those that underwent IST only (p<0.0001). Average LOS was highest in the group that had both therapies. ICU utilization was significantly higher in the transplant group that failed IST (P=0.0058). Overall inpatient cost of care across the cohort was $ 389,743,175. However cumulative adjusted charges were significantly different across the groups: a median of $244,513 for patients treated with IST, $793,009 for those who underwent SCT alone and $1,365,051 for those that had both forms of therapy (p <0.0001). The highest costs in each group correlated with pharmacy (37%), nursing and room/operating room (32%) charge codes. 84% of patients included originated from areas with urban zip codes without a significant difference in the payer mix (private or public insurance) for urban or rural patients. CONCLUSIONSThis is the first reported evaluation of inpatient resource utilization, mortality and costs in children treated for SAA in the US. While the overall cost of care for these patients is high, it is >3 fold higher for patients undergoing HSCT and over 6 times higher if HSCT is utilized upon failure of IST. With further comparative analyses, stakeholders can better understand where excess variation in care and cost occurs and define best practices required to further improve outcomes at lower cost. DisclosuresNo relevant conflicts of interest to declare.

Nontransplant therapy for bone marrow failure.

Nontransplant therapeutic options for acquired and constitutional aplastic anemia have significantly expanded during the last 5 years. In the future, transplant may be required less frequently. That trilineage hematologic responses could be achieved with the single agent eltrombopag in refractory aplastic anemia promotes new interest in growth factors after years of failed trials using other growth factor agents. Preliminary results adding eltrombopag to immunosuppressive therapy are promising, but long-term follow-up data evaluating clonal evolution rates are required before promoting its standard use in treatment-naive disease. Danazol, which is traditionally less preferred for treating cytopenias, is capable of preventing telomere attrition associated with hematologic responses in constitutional bone marrow failure resulting from telomere disease.

Shwachman-Diamond-Bodian Syndrome (SBDS): Long-Term Follow-Up of 31 Patients.

Shwachman-Bodian-Diamond syndrome (SBDS) is an autosomal recessive multisystem disorder primarily affecting the bone marrow, exocrine pancreas, and skeleton. As with other constitutional bone marrow failure syndromes, there is a predisposition to malignant myeloid transformation. The risk can only be estimated and varies considerably in the literature. Significant hematologic abnormalities can be present from early childhood with requirement of growth factor treatment (granulocyte-colony stimulating factor, erythropoietin). Since the first description of mutations in the SBDS gene, most clinically diagnosed patients have been genetically analyzed meanwhile, which now allows for genotype-phenotype correlations. Here, we report long-term clinical data of 31 SBDS patients (10 female, 21 male; 27 patients alive, 3 expired, 1 lost to follow up) with regard to different genotypes collected by the European Branch of the Severe Chronic Neutropenia International Registry since 1994: Severe Neutropenia (ANC <500/μl) is present in 11 patients, of whom 9 receive G-CSF treatment. In 16 of the remaining 22 untreated patients, the median ANC is below 1500/μl. G-CSF doses range from 0.4 to 7.7 μg/kg/day (mean G-CSF dose: 3.15 μg/kg/d). One patient is treated with granulocyte-macrophage colony stimulating factor (GM-CSF). Two of the G-CSF-treated patients have received a combination of G-CSF plus erythropoietin prior to stem cell transplantation. In 4 patients, G-CSF therapy was started within the first year of life, in 1 patient at the age of 20 months, and in 2 patients at the age of 8 and 13 years, respectively. MDS-like leukemic transformation occurred in 2 (1 male/1 female) out of 31 patients (6.5 %) at an age of 5.3 and 7.0 years. Both patients had additional cytogenetic abnormalities (monosomy 7 and complex aberrant karyotype). One patient had received G-CSF for 22 months at a dose of 3.8 μg/kg/d prior to SCT. In the other patient, pancytopenia including severe neutropenia started at the time cytogenetic aberrations were detectable. Both patients received stem cell transplantation (SCT) from unrelated donors (1 MUD, 1 haploident.). 14 months after MUD-SCT the girl is in a good clinical condition with full hematologic reconstitution, whereas the boy died within the first month after haploident. SCT from septicemia. SCT was also performed in 4 non-leukemic patients due to pancytopenia and prior to lung transplantation (2 HLA ident SCT: alive, 2 MUD SCT: 1 alive, 1 expired). SBDS gene analysis has been carried out in 14 of 19 German patients. Ten of 14 patients (71%) were compound heterozygous for 183–184TA>CT/258+2T>C. The rare genotypes 199A>G/258+2T>C, 297–300delAAGA/258+2T>C, and TGC>TGG/258+2T>C were observed in single patients. In another individual, a complex aberration with 7 mutations (Rosendahl et al, 2006) was found. Interestingly, two of the latter four patients presented with severe hematological anomalies early in life. One of them died from SCT after leukemic transformation. The third patient has developed severe osteoporosis and diabetes mellitus type 1. The fourth is on continuous G-CSF treatment. Our data demonstrate the importance of hematologic follow-up and regular cytogenetic evaluation of the bone marrow in SBDS patients. Patients with rare SBDS gene mutations seem to develop a more severe phenotype, but it requires a larger patient cohort for statistical proof.

Alternative Donor Stem Cell Transplantation after Reduced Intensity Conditioning Regimen for Patients with Bone Marrow Failure.

Allogeneic hematopoietic stem cell transplantation (HSCT) with HLA geno-identical sibling donor is the treatment of choice for children and young adults with constitutional or acquired (SAA) bone marrow failure (BMF). However, results of unrelated HSCT for BMF have been poorer due to high transplant related mortality mainly related to rejection and GVHD. Generally, a myeloablative regimen HSCT is used for acquired and some constitutional BMF but not for Fanconi anemia (FA) patients for whom a low dose conditioning regimen is employed. We have driven the hypothesis that immunosuppressive reduced intensity conditioning regimen should decrease TRM, decreasing GVHD and allowing engraftment. In a Phase I-II trial, 20 patients (pts) with BMF were enrolled and transplanted between 2002 and 2004. Thirteen pts had a constitutional aplasia: FA n=11, congenital megakaryocytopenia (CMK) n=1, Rothmund-Thomson syndrome n=1 and 7 pts had SAA among those two had paroxystic nocturnal hemoglobinuria (PNH). There were 12 male and 8 female. Median age was 8 years for constitutional BMF and 26 years for SAA. The HSC source was bone marrow for 11 pts, PBSC for 1 pt and cord blood for 8 pts. Ten of the twelve BM or PBSC donors were HLA matched for 10 loci (A, B, C, DRB1, and DQB1) and eight cord blood donors were HLA mismatched with 2 generic differences and were used for FA. All pts received the same conditioning regimen consisting of Busulfan (3mg/kg x 2), cyclophosphamide (10mg/kg x 4), fludarabine (30mg/m2 x3) and ATG (2.5mg/kg x4). The mean of nucleated stem cells infused and CD34 + cells was 2.8x108/kg and 5.9x106/kg respectively for the 12 pts who received BM stem cells and PBSC and 6.4x107/kg and 4.6x106/kg respectively for the eight pts who received CB cells. Acute GVH disease prophylaxis consisted of ciclosporine A (CsA) for pts with constitutional BMF and CsA and short course methotrexate for 6 of the 7 pts with acquired BMF, (one received tacrolimus instead of CsA due to thrombotic pre-existing co-morbidity). One pt (with CMK) died on day 0 from cerebral haemorrhage. Eighteen pts out of 19 had WBC recovery with a median time of 23 days (11–42); one FA pt did never reach sustained engraftment and died at D+291 from adenovirus infection. Three others had late graft rejection: in a context of acute GvHD and EBV infection and pulmonary aspergillosis for two pts with SAA who received BM graft and with acute GvHD and adenovirus infection for one FA pt who received CB graft. The conditioning was well tolerated without severe mucositis even in FA patients, sixteen patients experienced transient liver abnormalities. Nine patients developed reversible haemorrhagic cystitis at a median of 47 days post-transplant. There were 3 bacterial, 10 viral and 5 fungal infections with a cumulative incidence of TRM at one year of 45 ±24%. The cumulative incidence of acute GVH (II–IV) was 50 ±23%. Overall survival (OS) at one year was 55±11 %. It was 86%± 13 for SAA and 38% ± 13 for constitutional BMF. In spite of the short follow-up and few patients included, reduced intensity conditioning regimen provides encouraging results for patients with SAA. For constitutional BMF, low toxicity was observed, however the overall results seem similar to those reported in the literature using other RIC regimen and are probably related to other factors than the conditioning regimen.

Of the Telomerase RNA (TERC) and Telomerase Reverse Transcriptase (TERT) in Japanese Children with Aplastic Anemia.

It is well known that the incidence of aplastic anemia (AA) is much higher in Japan than in Western countries. However the reason for this finding is not known. Genetic backgrounds related to AA may be different between populations. Recent studies have shown that some patients with apparently “acquired” AA have mutations in telomerase ribonucleoprotein complex genes such as TERC and TERT. We studied 96 Japanese children with acquired AA (age range, 0–16 years; median, 7 years) and 59 healthy controls for mutations in TERC and TERT genes. Of these children, 35 were classified as having nonsevere AA, 39 as having severe AA, and 22 as having very severe AA. In 7 patients, AA was secondary to acute hepatitis. We extracted DNA samples from peripheral blood and all exons and flanking introns of TERT and TERC were amplified by PCR using 19 primer pairs (1 TERC, 18 TERT). To determine the sequence, the PCR products were analyzed by ABI/PRISM 3100 automated sequencer. Telomere lengths of leukocytes were assessed by flow-FISH. For the TERC gene, no mutation was found. One polymorphism (n514 G>A) was observed in 57/96 (59.4%) of patients. The same substitutions were detected in 31/59 (52.5%) healthy controls. For the TERT gene, two novel heterozygous, nonsynonymous mutations were identified (exon5; n2045 G>A, exon6; n2177 C>T). These base substitutions introduce an amino acid change-G682D and T726M, respectively. Neither patient had any clinical characteristics suggesting constitutional bone marrow failure syndrome. The n2177C>T substitution was identified in a 9-year-old girl with very severe AA who failed to respond to immunosuppressive therapy. She received an allogeneic bone marrow transplant (BMT) from an unrelated donor, but did not engraft. She was then treated by a second BMT from an HLA haploidentical her mother. Her blood cells had a very short telomere compared with that of age-matched controls. Another patient carrying the n2045G>A substitution had nonsevere AA and did not require any specific medication for 8 years. Six polymorphisms in exons of the TERT gene were identified in 102 unrelated patients (n915 G>A, n2097 C>T, n2520 G>A, n2946 T>C, n3039 C>T, and n3366 G>A). The allele frequencies of these silent base substitutions were 38/192 (19.8%), 3/192 (1.6%), 1/192 (0.5%), 1/192 (0.5%), 57/192 (29.7%), 2/192 (1.0%), respectively. Additionally, we identified 5 polymorphisms in introns of the TERT genes in 64 patients (IVS4+143 A>G, IVS9+11 C>T, IVS13+45 C>T, IVS15+136 G>A, and IVS16+81 C>T). The frequencies were 52/192 (27.1%), 3/192 (1.6%), 7/192 (3.6%), 1/192 (0.5%), and 1/192 (0.5%), respectively. Except for two substitutions (n915G>A and IVS4+143A>G), the other 9 were not listed in the SNP database. We found a few patients with AA carrying mutations of telomerase ribonucleoprotein complex genes. Because the incidence of these mutations is not higher than that in Western populations, this genetic difference does not explain the higher incidence of AA in Japanese children.

Shwachman-Diamond syndrome

Shwachman-Diamond syndrome (SDS), described just under 40 years ago, is a rare, autosomal-recessive disorder usually manifest in infancy and characterized by exocrine pancreatic insufficiency, short stature, and bone marrow dysfunction. Additional clinical features include metaphyseal dysostosis, epiphyseal dysplasia, immune dysfunction, liver disease, growth failure, renal tubular defects, insulin-dependent diabetes mellitus, and psychomotor retardation. Hematological manifestations other than neutropenia include anemia, raised fetal hemoglobin (HbF) levels, thrombocytopenia, impaired neutrophil chemotaxis, and aplastic anemia; as with other constitutional bone marrow failure syndromes, there is a predilection to malignant myeloid transformation. No unifying pathogenetic mechanism(s) has yet been shown to be responsible for SDS, although new insights into the molecular, genetic, and cellular basis of this rare disease have recently been described. Semin Hematol 39:95-102. Copyright 2002, Elsevier Science (USA). All rights reserved.

Haematological abnormalities in Shwachman-Diamond syndrome.

We have analysed the haematological parameters in 21 patients with Shwachman-Diamond syndrome (SDS) seen over a 25-year period at our institution. Neutropenia, although present in all patients, was intermittent in two-thirds, constant in the rest and was associated with impaired chemotaxis in all of those patients tested. Fetal haemoglobin (HbF) was elevated in 80% of the patients at some stage, and anaemia and thrombocytopenia was documented in 66% and 24% respectively. Bone marrow samples were taken in over half of the patients. Myelodysplastic syndrome (MDS) developed in seven (33%) patients, five of whom had acquired clonal structural chromosome abnormalities in their bone marrows. In five of the patients with MDS (24%) transformation to acute myeloid leukaemia occurred. Like other constitutional bone marrow failure syndromes. SDS has a predilection to leukaemic transformation hitherto assumed to be in the region of 5-10%. The data presented here suggest that this figure probably represents an underestimate. Shwachman-Diamond syndrome is an interesting model of leukaemia development and greater understanding of the clinical spectrum of this rare disorder should produce further insights into its pathobiology.