Bloom's syndrome. XX. The first 100 cancers

As of 1996 the 100th cancer was diagnosed in Bloom's syndrome. The cancers have been regularly documented since 1960 in a program of surveillance referred to as the Bloom's Syndrome Registry. Tabulated here are their types and ages of onset. The 100 cancers arose in 71 of the 168 registered individuals. Represented in Bloom's syndrome are both the cancers that commonly affect the general population and the rare tumors of early childhood. This body of information has become sufficiently large to be useful to geneticists and physicians in advising affected families concerning cancer risk. Of more general significance, however, the distribution of cancer sites and types sets Bloom's syndrome apart from other cancer-predisposing genetically determined conditions, affirming its experimental value as a model for analyzing the nonenvironmental component in the etiology of the generality of human cancer.

Chromosome instability syndromes

Fanconi anaemia (FA), ataxia telangiectasia (A-T), Nijmegen breakage syndrome (NBS) and Bloom syndrome (BS) are clinically distinct, chromosome instability (or breakage) disorders. Each disorder has its own pattern of chromosomal damage, with cells from these patients being hypersensitive to particular genotoxic drugs, indicating that the underlying defect in each case is likely to be different. In addition, each syndrome shows a predisposition to cancer. Study of the molecular and genetic basis of these disorders has revealed mechanisms of recognition and repair of DNA double-strand breaks, DNA interstrand crosslinks and DNA damage during DNA replication. Specialist clinics for each disorder have provided the concentration of expertise needed to tackle their characteristic clinical problems and improve outcomes. Although some treatments of the consequences of a disorder may be possible, for example, haematopoietic stem cell transplantation in FA and NBS, future early intervention to prevent complications of disease will depend on a greater understanding of the roles of the affected DNA repair pathways in development. An important realization has been the predisposition to cancer in carriers of some of these gene mutations.

Molecular genetics of RecQ helicase disorders

The RecQ helicases belong to the Superfamily II group of DNA helicases, and are defined by amino acid motifs that show sequence similarity to the catalytic domain of Escherichia coli RecQ. RecQ helicases have crucial roles in the maintenance of genome stability. In humans, there are five RecQ helicases and deficiencies in three of them cause genetic disorders characterised by cancer predisposition, premature aging and/or developmental abnormalities. RecQ helicase-deficient cells exhibit aberrant genetic recombination and/or DNA replication, which result in chromosomal instability and a decreased potential for proliferation. Here, we review the current knowledge of the molecular genetics of RecQ helicases, focusing on the human RecQ helicase disorders and mouse models of these conditions.

Recommendations for Childhood Cancer Screening and Surveillance in DNA Repair Disorders

DNA repair syndromes are heterogeneous disorders caused by pathogenic variants in genes encoding proteins key in DNA replication and/or the cellular response to DNA damage. The majority of these syndromes are inherited in an autosomal-recessive manner, but autosomal-dominant and X-linked recessive disorders also exist. The clinical features of patients with DNA repair syndromes are highly varied and dependent on the underlying genetic cause. Notably, all patients have elevated risks of syndrome-associated cancers, and many of these cancers present in childhood. Although it is clear that the risk of cancer is increased, there are limited data defining the true incidence of cancer and almost no evidence-based approaches to cancer surveillance in patients with DNA repair disorders. This article is the product of the October 2016 AACR Childhood Cancer Predisposition Workshop, which brought together experts from around the world to discuss and develop cancer surveillance guidelines for children with cancer-prone disorders. Herein, we focus on the more common of the rare DNA repair disorders: ataxia telangiectasia, Bloom syndrome, Fanconi anemia, dyskeratosis congenita, Nijmegen breakage syndrome, Rothmund-Thomson syndrome, and Xeroderma pigmentosum. Dedicated syndrome registries and a combination of basic science and clinical research have led to important insights into the underlying biology of these disorders. Given the rarity of these disorders, it is recommended that centralized centers of excellence be involved directly or through consultation in caring for patients with heritable DNA repair syndromes. Clin Cancer Res; 23(11); e23-e31. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Immunological lesions in human uracil DNA glycosylase: association with Bloom syndrome

Three monoclonal antibodies that react with uracil DNA glycosylase of normal human placenta were tested to determine whether one of the antibodies could be used as a negative marker for Bloom syndrome. As defined by enzyme-linked immunosorbent assay, monoclonal antibody 40.10.09, which reacts with normal human glycosylase, neither recognized nor inhibited native uracil DNA glycosylase from any of five separate Bloom syndrome cell strains. Immunoblot analyses demonstrated that the denatured glycosylase protein from all five Bloom syndrome cell strains was immunoreactive with the 40.10.09 antibody. Further, each native enzyme was immunoreactive with two other anti-human placental uracil DNA glycosylase monoclonal antibodies. In contrast, ELISA reactivity was observed with all three monoclonal antibodies in reactions of glycosylases from 5 normal human cell types and 13 abnormal human cell strains. These results experimentally verify the specificity of the aberrant reactivity of the Bloom syndrome uracil DNA glycosylase. The possibility arises that determination of the lack of immunoreactivity with antibody 40.10.09 may have value in the early diagnosis of Bloom syndrome.

Chromosome instability syndromes

The chromosome instability syndromes, ataxia telangiectasia (A-T), Fanconi anaemia (FA) and Bloom syndrome (BS) have been known for many years. More recently Nijmegen breakage syndrome (NBS) and ataxia telangiectasia-like disorder (ATLD) have been identified. A-T, ATLD and NBS form a group of disorders all of which show very similar cellular features that result from the consequences of increased sensitivity to ionizing radiation (IR). They also share some clinical features, particularly A-T and ATLD, and all show an immunodeficiency. A-T and NBS both show a predisposition to lymphoid tumours. Fanconi anaemia can be caused by mutations in eight different genes, although the majority of mutations are accounted for by FANCA and FANCC. The very rare Bloom syndrome is caused by mutation in a single gene, BLM. An important feature which all of these disorders have in common is that the genes identified are involved in aspects of recombination repair of DNA damage.

Clinical features of Bloom syndrome and function of the causative gene, BLM helicase

Bloom syndrome is a rare autosomal recessive genetic disorder characterized by growth deficiency, unusual facies, sun-sensitive telangiectatic erythema, immunodeficiency and predisposition to cancer. The causative gene for Bloom syndrome is BLM, which encodes the BLM RecQ helicase homolog protein. The first part of this review describes a long-term follow-up study of two Bloom syndrome siblings. Subsequently, the focus is placed on the functional domains of BLM. Laboratory diagnosis of Bloom syndrome by detecting mutations in BLM is laborious and impractical, unless there are common mutations in a population. Immunoblot and immunohistochemical analyses for the detection of the BLM protein using a polyclonal BLM antibody, which are useful approaches for clinical diagnosis of Bloom syndrome, are also described. In addition, a useful adjunct for the diagnosis of Bloom syndrome in terms of the BLM function is investigated, since disease cells must have the defective BLM helicase function. This review also discusses the nuclear localization signal of BLM, the proteins that interact with BLM and tumors originating from Bloom syndrome.

Bloom syndrome in short children born small for gestational age: a challenging diagnosis

BACKGROUND

GH treatment has become a frequently applied growth-promoting therapy in short children born small for gestational age (SGA). In some disorders GH treatment is contraindicated, eg, chromosomal breakage syndromes. Bloom syndrome is a rare chromosomal breakage syndrome characterized by severe pre- and postnatal growth deficiency, a photosensitive facial erythema, immunodeficiency, mental retardation or learning disabilities, endocrinopathies, and a predisposition to develop a wide variety of cancers.

OBJECTIVE

We report 2 patients with Bloom syndrome illustrating the variety in clinical manifestations. They were initially diagnosed with short stature after SGA birth and Silver Russell syndrome and treated with GH.

CASES

Both patients presented with pre- and postnatal growth failure but no clear other characteristic features associated with Bloom syndrome. Photosensitive skin lesions developed only at a pubertal age and were minimal. Also, both children showed normal immunoglobulin levels, normal development, and no signs of endocrinopathies at start of GH. Dysmorphic features resembling Silver Russell syndrome were observed in both patients. Remarkably, during GH treatment IGF-1 levels increased to values greater than 3.5 SD score, with normal IGF binding protein-3 levels.

CONCLUSION

Short children born SGA comprise a heterogeneous group. Bloom syndrome should be tested for in children with consanguineous parents, dysmorphic features (particularly resembling Silver Russell syndrome), skin abnormalities, and/or IGF-1 levels greater than 2.5 SD score during standard GH treatment with normal IGF binding protein-3 levels.

Carrier Testing for Autosomal- Recessive Disorders

The aim of carrier testing is to identify carrier couples at risk of having offspring with a serious genetic (autosomal recessive) disorder. Carrier couples are offered genetic consultation where their reproductive options, including prenatal diagnosis, are explained. The Ashkenazi Jewish population is at increased risk for several recessively inherited disorders (Tay-Sachs disease, Cystic fibrosis, Canavan disease, Gaucher disease, Familial Dysautonomia, Niemann-Pick disease, Fanconi anemia, and Bloom syndrome). Unlike Tay-Sachs disease, there is no simple biochemical or enzymatic test to detect carriers for these other disorders. However, with the rapid identification of disease-causing genes in recent years, DNA-based assays are increasingly available for carrier detection. Approximately 5% of the world's population carries a mutation affecting the globin chains of the hemoglobin molecule. Among the most common of these disorders are the thalassemias. The global birth rate of affected infants is at least 2 per 1000 (in unscreened populations), with the greatest incidence in Southeast Asian, Indian, Mediterranean, and Middle Eastern ethnic groups. Carriers are detected by evaluation of red cell indices and morphology, followed by more sophisticated hematological testing and molecular analyses. The following issues need to be considered in the development of a carrier screening program: (1) test selection based on disease severity and test accuracy; (2) funding for testing and genetic counselling; (3) definition of the target population to be screened; (4) development of a public and professional education program; (5) informed consent for screening; and (6) awareness of community needs.

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 myelodysplasia, 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.

Bloom's syndrome. Clinical features and immunologic abnormalities of four patients

Immune function was studied in four patients (two girls and two boys, aged 30 months to 24 years) with documented Bloom's syndrome. Three patients had a decreased serum concentration of at least one subclass of immunoglobulins. All had normal or elevated proportions of circulating B cells but two of them had a decreased proportion of CD4-positive helper-inducer T cells. We consistently found a severely impaired in vitro proliferative lymphocyte response to the plant lectin pokeweed mitogen (PWM). This could not be overcome by using suboptimal or supraoptimal doses of PWM, or by adding recombinant interleukin 2. In vitro PWM-induced IgM production was absent or low in two of the three patients studied and this low production could not be increased by addition of hydrocortisone. T lymphocytes responded normally to the plant lectins phytohemagglutinin and concanavalin A. T cells preactivated with phytohemagglutinin also normally proliferated in response to interleukin 2. It has previously been shown that lymphocyte activation with PWM involves both B and T cells and proceeds via an alternative pathway. The data thus indicate that patients with Bloom's syndrome have a specific defect in this PWM-induced alternative pathway of lymphocyte activation.

Genodermatoses with malignant potential

PURPOSE OF REVIEW

The delineation of syndromes carrying a predisposition to malignancy has led to great insights into the molecular biology of malignancy. Many such syndromes have cutaneous findings which can precede the development of neoplasia. Early recognition of the cutaneous stigmata of the genodermatoses with malignant potential can lead to early diagnosis and initiation of proper screening and treatment when indicated.

RECENT FINDINGS

This article reviews 'classic' genodermatoses with malignant potential and highlights recent recommendations for screening and treatment. Additionally more recently delineated syndromes and their cutaneous findings are discussed.

SUMMARY

Certain inherited syndromes with a risk of neoplasia exhibit characteristic cutaneous findings. Recognition of these findings by the astute practitioner can lead to early intervention which can impact the course of these rare diseases.

Diabetes mellitus in a young man with Bloom's syndrome

Bloom's syndrome (BS) is a rare autosomal recessive genetic disorder in which diabetes mellitus unusually frequently develops as a complication. We report on a 21-year-old Japanese male patient with BS who exhibited impaired glucose tolerance (IGT) in the initial oral glucose tolerance test (OGTT) and had developed patterns of diabetes mellitus by the second OGTT at the 2-years-and-2-months follow-up. German and Passarge reported that the onset of diabetes in patients with BS was in late adolescence or early adulthood. Our results support the findings of German and Passarge. Therefore, when a person with BS reaches late adolescence or early adulthood, an OGTT is necessary to ascertain whether the patient has IGT or diabetes mellitus as a complication, regardless of whether or not diabetic signs such as glucosuria are present.

A case of Bloom syndrome with conjunctival telangiectasia

Bloom syndrome is a rare genodermatosis characterized by photosensitivity, telangiectasias, growth retardation and malignancies. Eye findings have rarely been mentioned in case reports of this syndrome. We report a child with Bloom syndrome who had pronounced bulbar conjunctival telangiectasia originally diagnosed as episcleritis. Bulbar telangiectasia are frequently described in other genodermatoses such as ataxia telangiectasia and hereditary hemorrhagic telangiectasia, but are infrequently noted in Bloom syndrome. Previously described eye findings in Bloom syndrome are reviewed and the differential diagnosis of bulbar telangiectasia is discussed.

Early-onset drusen in a girl with bloom syndrome: probable clinical importance of an ocular manifestation

Ophthalmic examination of a girl admitted with the complaint of growth failure revealed retinal hard drusen. It was surprising to observe drusen in a child because they represent an age-related degenerative change in normal individuals. After further evaluation, she was diagnosed to have Bloom syndrome, a premature aging syndrome. To the authors' knowledge, this is the first case of Bloom syndrome associated with drusen. It is probable that not only aging but also other fundamental cell processes, especially uncontrolled cell proliferation, might be similarly affected and might follow a more rapid course in this inherited condition presenting with drusen. The authors suggest paying extra attention to drusen during the ophthalmic assessment in the diagnosis of all Bloom syndrome patients; it may be prudent to watch more carefully for the development of cancer in patients with drusen than those without drusen.

Triple autosomal trisomy in a pregnancy at risk for Bloom's syndrome

Cytogenetic analysis of the products of conception in a pregnancy at risk for Bloom's syndrome (BS) documented the karyotype 49,XX, +2, +8, +11. Autosomal triple trisomy has previously been reported in abortuses but is exceedingly rare. Other interesting but previously unreported observations made during the present study were the following: BS in a Brazilian individual, the first instance of BS diagnosed in South America; transmission of the BS mutation in Jews that are non-Ashkenazi; a medulloblastoma in the propositus, the first malignant brain tumor reported in BS; and, as in all previously examined pregnancies at risk for BS, non-homozygosity for the BS mutation.

Diagnosis of Bloom's syndrome by sister chromatid exchange evaluation in chorionic villus cultures

Cultures of a chorion biopsy taken from a pregnancy at risk of Bloom's syndrome revealed the high sister chromatid exchange frequency diagnostic of this rare disorder. To obtain the result, cultures were grown under standard conditions, with the addition of 10 microM 5'-bromodeoxyuridine for the final 48 h of incubation. This result demonstrates the feasibility of early prenatal diagnosis of Bloom's syndrome.

Bloom's syndrome. Possible pitfalls in clinical diagnosis

We treated two patients with Bloom's syndrome and conducted extensive endocrine studies. In one patient, we studied longitudinal growth and pubertal development and the effect of exogenous human growth hormone on growth velocity. Establishing a diagnosis of Bloom's syndrome is difficult in clinical practice. Measurement of the frequency of sister chromatid exchanges is essential in patients with growth retardation of intrauterine origin.

Asymptomatic Bloom syndrome diagnosed by chance in a patient with breast cancer

Bloom syndrome (BS) is a rare genetic disorder caused by biallelic inactivation of the BLM gene, which usually manifests in childhood by significant growth retardation, immune deficiency, characteristic skin lesions, cancer predisposition and other distinguishable disease features. To our knowledge, all prior instances of BS have been identified via intentional analysis of patients with clinical suspicion for this disease or DNA testing of members of affected pedigrees. We describe an incidental finding of BS, which occurred upon routine germline DNA analysis of consecutive breast cancer patients. The person with the biallelic pathogenic BLM c.1642C>T (p.Gln548Ter) variant remained clinically healthy for 38 years until she developed breast cancer. Detailed examination of this woman, which was carried out after the genetic diagnosis, revealed mild features of BS. A sister chromatid exchange (SCE) test confirmed the presence of this syndrome. The tumor exhibited triple-negative receptor status, a high proliferation rate, a low tumor mutation burden (TMB), and a moderate level of chromosomal instability (homologous recombination deficiency (HRD) score = 29). The patient showed normal tolerability to radiotherapy and several regimens of cytotoxic therapy. Thus, some BS patients may remain undiagnosed due to the mild phenotype of their disease. BLM should be incorporated in gene panels utilized for germline DNA testing of cancer patients.

[Bloom syndrome. Clinical manifestations and cromosomal study in a Mexican child]

Bloom syndrome is an extremely rare inherited disorder. We present a case of Bloom syndrome with a chromosomal study in a Mexican five-year-old patient who presented growth retardation, narrow facies with poikiloderma, café-au-lait, macules and photosensitivity.

Photosensitivity and photodermatitis in childhood

Photosensitivity disorders of children are uncommon, except for banal overexposure reactions to sunlight. Although the long-term sequelae of chronic or intense sun exposure are not often seen in children, physicians should advise patients of the harmful effects and irreversible skin damage that results from unduly prolonged sun exposure. Damage accumulates over the years to cause premature aging, senile elastosis, actinic keratoses, and squamous- and basal-cell carcinomas. Besides the pigmentary changes, wrinkles, and skin cancers--genuine sources of altered appearance and morbidity--we now know that sunburned children develop a higher incidence of melanoma, which is not a rare cause of death in young adults. In Australia, where the incidence of melanoma is highest, a strong correlation exists for melanoma in children who get sunburn before the age of 10. Also, the incidence of melanoma is 50 times as great in bikini wearers who get sunburn as in girls who wear one-piece bathing suits.