Dyskeratosis congenita: clinical features and genetic aspects. Report of a family and review of the literature.

A large family with dyskeratosis congenita is reported. There were nine affected males, the findings in five of who are reported. We review 46 cases selected from the literature. The cardinal findings of this inherited multisystem disorder are delineated from these 51 cases. The complications of the disease, including opportunistic infection, are described. The parallel is made between dyskeratosis congenita and Fanconi's anaemia. The X-linked transmission of dyskeratosis congenita is confirmed by the family pedigree in this report. From the analysis of the families reported in the literature, there appears to be genetic heterogeneity in this disease. This study in our family indicates absence of close linkage between the Xga locus and the X-linked recessive form of dyskeratosis congenita.     

Sister chromatid exchanges in leukemic patients

Sister chromatid exchange (SCE) was studied in PHA-stimulated peripheral blood lymphocytes from 36 newly diagnosed and untreated leukemic patients: 16 with acute lymphoblastic leukemia (ALL), 10 with acute nonlymphocytic leukemia (ANLL), and 10 with chronic myelocytic leukemia (CML). The metaphases analyzed show no chromosomal abnormalities. The mean SCE frequency (mean +/- SE) for each group of patients was: 6.8 +/- 0.4, 6.6 +/- 0.3, and 7.0 +/- 0.6 per mitosis, respectively, which was significantly lower than the mean SCE score for 30 controls (8.7 +/- 0.2). No differences in SCE score among ALL, ANLL, and CML and a similar SCE frequency by chromosome number and group allowed consolidation of all the cases into a single group of 36 leukemic patients (6.8 +/- 0.3). When the frequency of SCE was compared by chromosome number and group between the leukemic patients with the control group, a significant decrease in SCE frequency was observed due to a low SCE score in almost all the complements, except chromosome #1. It is suggested that the low SCE rate is related to the leukemic process itself.     

Heterozygote detection through bleomycin-induced G2 chromatid breakage in dyskeratosis congenita families.

We determined the mean number of chromatid breaks per cell (b/c) in the bleomycin-treated lymphocytes of 10 patients with dyskeratosis congenita (DC) and 26 of their relatives to ascertain whether bleomycin sensitivity would distinguish DC heterozygotes from normal individuals. We observed a significantly higher mean number of chromatid b/c in DC patients and obligate heterozygotes (patients versus controls, p less than 0.0001; heterozygotes versus controls, p = 0.0076, Mann-Whitney rank-sum test). Unequivocal heterozygote detection was not possible owing to overlap of the b/c values of patients, heterozygotes, and controls, but our findings provided strong evidence of a link between autosomal recessive as well as X-linked recessive DC mutations and bleomycin sensitivity in homozygous, hemizygous, and heterozygous individuals.     

Deficient natural killer cell activity in a patient with Fanconi''s anaemia and squamous cell carcinoma. Association with defect in interferon release.

A child with Fanconi's anaemia diagnosed at 7 years of age presented in adult life with lymphopenia, recurrent warts and Bowen's disease. The latter resulted in the development of multiple cutaneous squamous cell carcinomas which metastasized to the skeleton. Investigation of her immune function revealed selective defects in natural killer (NK) cell activity. Humoral immunity and several tests of cell-mediated responses were within normal or became normal after treatment with levamisole or transfer factor. Analysis of the defect in NK activity revealed that low levels could be induced in vitro by fibroblast interferon. Stimulation of blood lymphocytes from the patient with the interferon inducer poly (I)-poly (C) resulted in an increase in NK activity but incubation of her lymphocytes on tumour cells did not result in an increase in NK activity or the release of interferon. This contrasted with the marked increase in NK activity and interferon release observed when lymphocytes from normal controls were incubated on tumor cells. These findings suggested the absence of NK activity in this patient was secondary to a defect in interferon release from lymphocytes on exposure to tumour antigens. It is considered that these defects may have been an important predisposing factor in the development of malignancy in this patient and possibly other patients with Fanconi's anaemia.     

Antilymphocyte globulin (ALG) or antithymocyte globulin (ATG) with methylprednisone and oxymethalone in aplastic anaemia

From 1986 to 1994 we treated 26 patients of aplastic anaemia between 6 to 61 years age group with ATG/ALG, Methylprednisone and Oxymethalone. Five had very severe aplastic anaemia, 16 had severe and 5 nonsevere disease. Disease was associated with hepatitis in 5 patients and with pregnancy and drug use in 2 patients each. In others no cause could be ascertained. A total of 31 courses of treatment were given (range 1-3 courses per patient). Nine patients had complete response (34.62%) and 3 had partial response (11.54%) with an overall response rate of 46.16%. Four patients died within 2 months of starting the treatment. The median follow up was 24 months (range 6-102 months) with an overall survival probality of 45% at 2 yr. At the time of evaluation 12 patients have died, 9 are alive disease-free and 5 are alive with disease. The side effects associated with therapy were tolerable and did not require cessation of therapy in any patient. We conclude that ATG/ALG with Methylprednisone and Oxymethalone is beneficial to significant number of patients with aplastic anaemia.     

Clinical and cytogenetic diversity in Fanconi''s anaemia.

Abnormally high levels of spontaneous and mitomycin C or diepoxybutane induced chromosome breakage were observed in lymphocytes from eight out of nine previously undescribed patients clinically diagnosed as having Fanconi's anaemia. The results suggest that the combination of spontaneous and induced chromosome breakage is a good aid in the differential diagnosis and we suggest that increased chromosome breakage is pathognomonic for this recessive disorder. It is, however, not possible to demonstrate consistently raised levels of induced chromosome breakage in obligate carriers. The patient who had normal levels of chromosome breakage had an atypical haematological picture and may suffer from a disease genetically different from Fanconi's anaemia.     

Sister chromatid exchanges and ion release in patients wearing fracture fixation devices

The quantification of sister chromatid exchange (SCE) during mitosis is a useful index for evaluating genotoxic effects in subjects occupationally or incidentally exposed to potentially toxic substances. The authors investigated the hypothesis that ions released by corrosion from prosthetic components of fracture fixation devices are associated with change in SCE incidence. In the present study, ten patients with implants were examined, and fifteen subjects with no implants were used as controls. SCE and high frequency cell (HFC) numbers were evaluated in circulating lymphocytes. In addition, nickel (Ni) and chromium (Cr) ion values in the serum were measured because, after iron, these metals are major components of stainless steel. A significant increase in SCE numbers was observed in patients compared to the control population (4.9 +/- 1.3 vs. 3.5 +/- 1.4). Ni concentration was 1.71 +/- 1.49 ng/mL in patients and 0.72 +/- 0.52 ng/mL in control subjects; Cr concentration was, respectively, 1.01 +/- 0.77 ng/mL and 0.19 +/- 0. 27 ng/mL. The increase of serum Cr and Ni was statistically significant. No correlation was found between the increased Cr concentrations and SCE number while Cr ion levels were found to be significantly correlated to HFC. An inverse correlation between Ni level and SCE numbers was observed. Our findings suggest that Cr release by stainless steel implants could have a genotoxic effect; thus it would be useful to carefully monitor implanted subjects with regard to serum ion dosage, SCE analysis, and HFC evaluation. In any case, it would be appropriate to remove the implant when fracture fixation is reached.     

1.4 Mb candidate gene region for X linked dyskeratosis congenita defined by combined haplotype and X chromosome inactivation analysis.

Dyskeratosis congenita (DC) is a rare inherited disorder characterised by the early onset of reticulate skin pigmentation, nail dystrophy, and mucosal leucoplakia. In over 80% of cases bone marrow failure develops and this is the main cause of early mortality. The DC1 gene responsible for the X linked form (MIM 305000) of dyskeratosis congenita has been mapped to Xq28. In order to narrow the candidate gene region, genetic linkage analysis was performed in eight X linked pedigrees using a set of markers spanning Xq28. A maximum lod score of 5.31 with no recombinations was achieved with marker DXS1073. Two recombination events were identified; one of these uses X chromosome inactivation pattern analysis to determine carrier status and haplotype analysis to fine map the recombination breakpoint. The fine mapping of these recombination events has enabled the candidate gene region for X linked dyskeratosis congenita to be defined as the 1.4 Mb interval between Xq3274 and DXS1108.     

Interferon response of lymphocytes in disorders with decreased resistance to infections

Interferon production was induced by Sendai and Newcastle disease virus in blood obtained from patients with Down's syndrome (eight cases), Fanconi's anaemia (one case), subacute sclerosing panencephalitis (one case), blast cell leukaemia (nine cases), chronic lymphocytic leukaemia (six cases) and control subjects. The titres per millilitre of blood varied greatly, but the interferon response per lymphocyte was comparatively constant in all groups with the exception of chronic lymphocytic leukaemia, where the cells displayed a markedly reduced interferon-producing ability.     

Sister chromatid exchanges in patients with carcinoma in situ of cervix uteri.

Sister chromatid exchange (SCE) was analyzed in lymphocytes of 21 patients with carcinoma in situ of cervix uteri and 19 control subjects. The mean SCE frequencies were 8.92 +/- 0.31 (n = 417) and 6.94 +/- 0.23, (n = 375) per metaphase in patients and controls, respectively. The increase of SCE levels in cancer patients was highly significant in respect to controls (p less than 0.001). Together with data of other authors in patients with precancerous and cancerous lesions of the cervix, our results suggest that there is no correlation between SCE rate and severity of cancerous lesions.     

Sister chromatid exchange in malignant lymphomas

Sister chromatid exchange (SCE) was evaluated in peripheral lymphocytes from 20 untreated patients with malignant lymphomas: 6 with Hodgkin's disease (HD), 14 with non-Hodgkin lymphoma (NHL), and 5 with lymphadenitis. The mean SCE frequency (+/- SE) was: 11.2 +/- 0.6, 11.0 +/- 0.6, and 7.2 +/- 0.3 for HD, NHL, and lymphadenitis patients, respectively, and 8.7 +/- 0.2 for the control group. No differences in SCE score were observed in HD and NHL. These results allowed us to consider both groups (HD and NHL) as a single neoplastic population (mean +/- SE, 11.0 +/- 0.4). No significant differences were found between the lymphadenitis and control groups. On the other hand, significantly higher SCE scores were seen in neoplastic populations than in the control and lymphadenitis groups (p less than 0.001 and p less than 0.01, respectively). When SCE was compared by chromosome number and group between neoplastic patients and controls, a higher SCE frequency was observed in chromosomes #1, #2, #3, and B, C + X, E, F chromosome groups than in controls. SCE levels were significantly higher in lymphoma patients in all chromosome numbers and groups mentioned than in patients with lymphadenitis. It is suggested that the high SCE rate in the malignant lymphoma population is possibly related to an increased chromosomal instability.     

Dyskerin and cancer: more than telomerase. The defect in mRNA translation helps in explaining how a proliferative defect leads to cancer

Point mutations in the DKC1 gene that encodes dyskerin cause the rare inherited syndrome called X-linked dyskeratosis congenita, characterized by a failure of proliferating tissues and increased susceptibility to cancer. Dyskerin is a nucleolar protein with different functions, all fundamental to basic cellular events such as protein expression, growth, and proliferation. The two best-characterized dyskerin activities are the stabilization of the telomerase RNA component, allowing the proper function telomerase enzymatic complex, and the modification of specific uridine residues of ribosomal RNA by converting them to pseudouridine, thus allowing proper ribosome processing and function. In light of the recent findings, this review focuses on the molecular pathogenesis of dyskeratosis congenita, discussing how a defect in ribosomal function might impact on the translation of a subset of mRNAs encoding for tumour suppressors, thus providing an explanation for the apparent paradox of dyskeratosis congenita in which reduced cell proliferation is associated with cancer susceptibility. In addition, the current evidence pointing to a role played by dyskerin in tumours in the general population is also discussed.     

The effect of tobacco smoking on the frequency of sister chromatid exchanges in human lymphocyte chromosomes

The incidence of sister chromatid exchange (SCE) was investigated in the lymphocyte chromosomes of 24 bidi smokers, 18 cigarette smokers, and 20 normal nonsmoking controls. Bidi and cigarette smokers had a mean SCE per cell of 10.12 +/- 2.41 and 8.15 +/- 1.62, respectively, which were significantly higher than the mean value of 5.48 +/- 1.29 found in controls. Higher frequencies of SCE were also observed in individuals who smoked more than ten bidis or cigarettes per day, compared with people who smoked less than ten bidis or cigarettes per day, respectively. Individuals who smoked bidis or cigarettes for more than 10 years also showed an increased frequency of SCE as compared with those who smoked bidis or cigarettes for less than 10 years.     

The pathology of bone marrow failure

Leguit R J & van den Tweel J G
(2010) Histopathology 57 , 655–670
The pathology of bone marrow failure An important indication for bone marrow investigation is the presence of bone marrow failure, which manifests itself as (pan)cytopenia. The causes of cytopenia are varied and differ considerably between childhood and adulthood. In the paediatric age group inherited bone marrow failure syndromes are important causes of bone marrow failure, but they play only a minor role in later life. This review gives a comprehensive overview of bone marrow failure disorders in children and adults. We classified the causes of bone marrow failure according to the main presenting haematological abnormality, i.e. anaemia, neutropenia, thrombocytopenia or pancytopenia. The following red cell disorders are discussed: red cell aplasia, sideroblastic anaemia, congenital dyserythropoietic anaemia, haemolytic anaemia, paroxysmal nocturnal haemoglobinuria, iron deficiency anaemia, anaemia of chronic disease and megaloblastic anaemia. The neutropenias occur in the context of Shwachman–Diamond syndrome (SDS), severe congenital neutropenia, cyclic neutropenia, immune‐related neutropenia and non‐immune neutropenia. In addition, the following causes of thrombocytopenia are discussed: congenital amegakaryocytic thrombocytopenia, thrombocytopenia with absent radii, immune‐related thrombocytopenia and non‐immune thrombocytopenia. Finally, we pay attention to the following pancytopenic disorders: Fanconi anaemia, dyskeratosis congenita, aplastic anaemia, myelodysplastic syndromes and human immunodeficiency virus (HIV) infection.     

Dyskeratosis congenita with linear areas of severe cutaneous involvement

Dyskeratosis congenita (DC) is a rare hereditary disorder of skin which may be associated with aplastic anemia. The pattern of inheritance is X-linked recessive in most instances, but autosomal dominant and autosomal recessive types have been documented. Reticulated hyperpigmentation usually is the first manifestation. The pigmentary changes may be limited to neck, upper chest, and proximal parts of the limbs initially but within affected areas the involvement is always diffuse. We report on a patient with typical diffuse cutaneous signs of dyskeratosis congenita superimposed with hyperpigmentation that was more pronounced along Blaschko's lines. To explain this phenomenon, we assume that the patient has the autosomal dominant type and that loss of heterozygosity occurred in a somatic cell giving rise to a population of cells that migrated along these lines during embryogenesis. Am. J. Med. Genet. 75:492–496, 1998. © 1998 Wiley-Liss, Inc.     

Dyskeratosis congenita: an autosomal recessive variant

We describe a woman with dyskeratosis congenita (DKC), microcephaly, and a purple discoloration of the tongue. The latter findings are not commonly described in males with DKC, have been reported in another female patient with this condition, and may represent the phenotype of an autosomal recessive entity of DKC. Results of X chromosome inactivation studies did not support X-linked DKC in our family. The additional findings of an affected brother and parental consanguinity support the hypothesis of autosomal recessive inheritance.     

Adriamycin-induced sister chromatid exchange and chromosomal aberrations in Down's syndrome lymphocytes.

Blood samples from six Down's syndrome (DS) and six age- and sex-matched controls were cultured for 72 h in the presence of BrdUrd. Lymphocytes were then analysed at their second mitosis for sister chromatid exchange (SCE) and at their first mitosis for chromosome aberrations. Treatment with adriamycin (30 and 60 ng) showed a significant increase in frequency of SCE and chromosome aberrations in DS lymphocytes compared to normal lymphocytes at initiation of culture. Cells treated with adriamycin (ADR) for the last 24 h also showed a significant increase in SCE in DS lymphocytes compared to normal lymphocytes. A significant increase in chromatid-type aberrations was also recorded in DS lymphocytes after both treatments cultured for the last 24 h.     

Sister chromatid exchanges in patients with oral submucous fibrosis

The incidence of sister chromatid exchange (SCE) was investigated in the lymphocyte chromosomes of 45 patients with oral submucous fibrosis and 56 age- and sex-matched nonsmoking controls. The frequency of SCE was 9.26 +/- 2.15 in patients with oral submucous fibrosis, which was significantly higher than the mean SCE value of 5.49 +/- 1.24 observed in normal controls. The frequency of SCE in patients with oral submucous fibrosis addicted to the habit of betel with tobacco chewing, "bidi"/cigarette smoking and combined habits of chewing and smoking of tobacco were 8.12 +/- 1.69, 9.43 +/- 1.87, and 10.06 +/- 2.28, respectively. These values were also significantly higher as compared with the SCE values observed in normal controls.     

Cytogenetic and cytokinetic analysis of lymphocytes from patients with hereditary adenomatosis of the colon and rectum

The frequencies of chromosome aberrations, sister chromatid exchanges (SCEs), and cell cycle kinetics were examined in cultured lymphocytes from five patients with hereditary adenomatosis of the colon and rectum (ACR) [three patients with Gardner's syndrome (GS) and two patients with familial polyposis coli (FPC)]. The frequency of numerical chromosome aberrations was no different in metaphase cells at the first and second replication cycles (M1 and M2) in the ACR patients and control subjects. The percentage of structural chromosome aberrations in both M1 and M2 cells was somewhat higher in the ACR patients as compared with the controls. Neither spontaneous nor mitomycin C-induced SCE frequencies in the patients with ACR were different from the controls, except for one patient with GS, who showed a remarkably high spontaneous SCE frequency. This patient is the mother of a son who had hepatoblastoma. The cell replication index (RI) was lower in the GS patients than in the controls. However, the RI in the FPC patients did not differ from that of the controls.     

Retinoblastoma in association with the chromosome breakage syndromes Fanconi's anaemia and Bloom's syndrome: clinical and cytogenetic findings

Two children presenting with sporadic unilateral retinoblastoma and exhibiting a high degree of chromosome breakage were noted to have unusual facies, microcephaly and abnormal skin pigmentation. In the first child the pattern of both spontaneous and mitomycin-C-induced chromosome breakage was characteristic of Fanconi's anaemia although the degree of breakage was extreme. She also exhibited a striking increase in X-ray-induced chromosomal damage in G₀ lymphocytes as measured by dicentric formation and increase in chromatid-type aberrations. She had a number of typical clinical features, including cafe-au-lait patches and abnormalities involving the kidney; however, she demonstrated neither the hypoplasia of radius and thumb nor the typical aplastic phase of this disorder. At age 22 months the child became anaemic with trilineage myelo-dysplasia, which was rapidly followed by the development of acute myeloblastic leukaemia. The early onset (at age 4 months) of retinoblastoma may have been associated with the underlying genomic instability. The second child exhibited a pattern of chromosome breakage characteristic of Bloom's syndrome, in addition to a moderate increase in damage induced by mytomycin-C. She had the typical stunted growth and malar hypoplasia of Bloom's syndrome although she did not demonstrate the frequently described erythematous 'butterfly rash'. Although patients with Fanconi's anaemia and Bloom's syndrome are recognised to be at an increased risk of cancer, retinoblastoma has not previously been described in patients with either condition. We suggest that underlying recessive chromosome breakage syndromes may be underdiagnosed in paediatric cancer patients, with important implications for prognosis and genetic counselling.