Fenótipos de imunodeficiência em dois irmãos com Síndrome de Bloom / Immunodeficiency phenotypes in two siblings with Bloom Syndrome

A síndrome de Bloom é um raro distúrbio de instabilidade cromossômica, devido a defeitos de reparo do DNA. O gene responsável BLMfoi mapeado no cromossomo 15q e causa redução significante da expressão da enzima DNA-helicase no núcleo celular. Esta enzima é importante para os mecanismos de reparo do DNA. Pacientes geralmente apresentam elevada suscetibilidade para desenvolvimento de câncer e infecções, bacterianas recorrentes. Nós avaliamos o sistema imunológico de dois irmãos (menino de 13 anos e menina de 6 anos) com síndrome de Bloom, os quais tinham similar suscetibilidade para infecções respiratórias recorrentes, mas diferentes anormalidades imunológicas. O menino apresentou níveis persistentemente baixos de IgM e de células CD4+. Os níveis de IgA diminuíram quando ele tinha 11 anos. A menina apresentou níveis persistentemente baixos dos níveis de IgM e IgA, e não respondeu à vacina polissacarídica. Os níveis de IgG diminuíram quando ela tinha 6 anos. As diferentes anormalidades imunológicas são discutidas

Recent advances in chromosome breakage syndromes and their diagnosis.

Chromosome instability is a characteristic cytogenetic feature of a number of genetically determined disorders collectively called as the chromosome breakage syndromes or DNA-repair disorders. They are characterized by susceptibility to chromosomal breakages, increased frequency of breaks and interchanges occurring either spontaneously or following exposure to various DNA-damaging agents. These diseases are a group of genetic disorders sharing a number of features. They are all autosomal recessive, show an increased tendency for chromosomal aberrations and to develop malignancies. The principal diseases in this group having a diverse etiology and clinical manifestations include Fanconi anemia (FA), ataxia telangiectasia (AT), Nijmegen breakage syndrome (NBS), Bloom syndrome (BS), xeroderma pigementosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD). The underlying defect in these syndromes is the inability to repair a particular type of DNA damage. A number of repair disorder phenotypes are caused by more than one gene. The diagnosis of these syndromes is made by the characteristic clinical features specific to each disease, but the definitive diagnosis is achieved by laboratory investigations such as cytogenetic, biochemical and molecular methods. The importance of prenatal diagnosis and our experience are discussed in this article.

Malformaciones genéticas y talla baja / Genetic malformations and low stature

Pra el médico pediatra es muy importante reconocer en aquellos pacientes con talla baja la posible asociación con un genotopatía. A continuación se revisan algunos de los síndromes malformativos que presentan características comunes y los hallazgos clínicos más frecuentes

Bloom syndrome: is the gene mapped to the point?

Bloom syndrome (BS), an autosomal recessive genetic disorder, is an instructive model to explore variety of questions in "deregulation of normal cell functioning". Most of the BS patients are homozygous for mutant BLM gene and depict high sister chromatid exchanges (SCEs) in almost all the cells. However, a few possess cells with dimorphic SCE phenotype. A majority of patients with dimorphic SCE phenotype have been suggested to be compound heterozygotes, inheriting two different mutations in the BLM locus from each parent. An intragenic somatic recombination event in a precursor stem cell in such patients is envisaged to give rise to a population of cells with functionally wild-type (BLM) gene and normal SCE phenotype. Adopting unique dual approaches of positional mapping through "homozygosity by descent" and "somatic crossover point mapping", a candidate for BLM has been identified and localized to a 250 Kb interval between polymorphic loci, DI5S1108 and D15127. The sequence has been found to encode a 1417 amino acid peptide with homology to the RecQ helicases, a sub-family of DExH box-containing DNA and RNA helicases. The presence of chain terminating mutations in the 'candidate' gene in BS patients has suggested it to be the BLM gene. Apparantly the proposed gene product does not seem to provide answer for a variety of clinical, biochemical and experimental observations made in BS or BS cells till date. Our recent observation of a significant decrease in the activity of pyruvate kinase in three BS B-lymphoblastoid cell lines when compared to a similar cell line established from a normal healthy subject presents with another possible candidate to elucidate the defects in BS. Experiments using okadaic acid, a phosphatase-2a/1 inhibitor, have depicted in our study that many of the clinical features characteristic of BS, not easily explanable by the recently proposed BLM gene, can be explained by the deficiency in the PK alone and/or PP2a/PP1 activity.

report on three cases of Bloom's syndrome or congenital telangiectatic erythema and stunted growth

Bloom's syndrome is a rare autosomal recessive syndrome characterized by telangiectatic erythema of face and back of the hands, short stature, distinctive facies, abnormal immune response, and predisposition to malignancy, especially leukemia. Chromosomal abnormalities are hallmarks of the disorder and a high frequency of sister chromatid exchanges and quadriradial configurations in lymphocytes are virtually diagnostic. Approximately 110 cases have been reported throughout the world up to 1983

Síndrome de Bloom familiar associada a neuroblastoma / Familial Bloom's syndrome associated with neuroblastoma

A SB é entidade rara, de herança autossômica recessiva e caracterizada por baixa estatura, sensibilidade solar e eritema malar telangiectásico. E classificado como doença de quebra cromossômica e imunodeficiência primária mista e maior incidência de neoplasias têm sido relatadas em associaçäo. Apresentamos dois irmäos com SB e imunodeficiência associada. As crianças, ambas do sexo masculino, tinham cinco anos (A) e quatro anos (B) de idade, quando do diagnóstico. O paciente A tinha história de diarréia crônica, otite supurada, rinite purulenta, conjuntivite e piodermite recorrentes. O paciente B, internado por massa abdominal, teve diagnóstico de neuroblastoma bilateral e näo apresenta quadro infecciosos de repetiçäo. Foi submetido a ressecçäo tumoral e quimioterapia, apresentando a seguir monilíase oral, gengivoestomatite herpética e abscessos cutâneos. Os dois pacientes revelaram as características clínicas da SB. A avaliaçäo imunológica, näo observamos alteraçöes no sistema de complemento. Os níveis de IgG, IgA, IgM e IgA salivar foram, respectivamente de: 455mg/dl, 20mg/dl e 0,6mg/dl para A e 400mg/dl, 15mg/dl, 20mg/dl e 0,2mg/dl para B. Os dois apresentaram títulos de anticorpos antipólio (1, 2 e 3) e iso-hemaglutinas antiA em títulos baixos. A tipagem dos linfócitos T, foram observados, para A: OKT3 = 66%, OKT4 = 33,1%, OKT8 = 32,9% e relaçäo OKT4/4 = 1,0 e para B OKT4 = 70%, OKT4 = 32,5%, OKT8 = 34% e relaçäo OKT 4/8 = 1,0. A cultura de linfócitos estimulada com PHA foi...

Bloom syndrome in a Brazilian child

Os autores descrevem o caso de um menino com quadro clínico característico da síndrome de Bloom e uma alta freqüência quadrirradiais, quebras cromossômicas e outras aberraçöes cromossômicas estruturais

A Case of Familial Telangiectasia of Face / 대한피부과학회지

A case of familial telangiectasia of face resembling lupus erythematosus but no having other involved symptoms, except ichthyosis vulgaris of lower legs in all 4 sisters, appeared on 8 months through 2 years after birth is reported Authors suggest this case to be simplified congenital telangiectasia of face, because of not consisted with preexistiong various diseases such as Bloom's syndrome, Ataxia-Telangiectasia, Rothmund-Thomsons' Syndrome, Dyskeratosis congenita, and Cockayne's syndrome, which show the familial telangiectasia of face.