Isodisomy of chromosome 6 in a newborn with methylmalonic acidemia and agenesis of pancreatic beta cells causing diabetes mellitus

Isodisomy (ID) is a genetic anomaly defined as the inheritance of two copies of the same genetic material from one parent. ID in an offspring is a rare cause of recessive genetic diseases via inheritance of two copies of a mutated gene from one carrier parent. We studied a newborn female with a mut(o) of methylmalonic acidemia and complete absence of insulin-producing beta cells in otherwise normal-appearing pancreatic islets, causing insulin-dependent diabetes mellitus. The patient died 2 wk after birth. Serotyping of the HLA antigens, DNA typing of HLA-B and HLA class II loci, study of polymorphic DNA markers of chromosome 6, and cytogenetic analysis demonstrated paternal ID, involving at least a 25-centiMorgan portion of the chromosome pair that encompasses the MHC. ID probably caused methylmalonic acidemia by duplication of a mutated allele of the corresponding gene on the chromosome 6 inherited from the father. It is also very likely that ID was etiologically related to the agenesis of beta cells and consequent insulin-dependent diabetes mellitus in our patient. We thus speculate on the existence of a gene on chromosome 6 involved in beta cell differentiation.

Granulocytic sarcoma showing chromosomal changes other than the t(8;21)

Cytogenetic analysis of a granulocytic sarcoma showed a 46,XX,der(X)t(X;1) (q28;q22), inv(3)(p21q27), inv(9)(p13q22),t(12;22)(p11;q11) karyotype. In addition, bone marrow aspirate disclosed the presence of cells with a 46,XX,inv(3)(p21q27),inv(9)(p13q22)(p11;q11) chromosomal pattern while the patient was clinically aleukemic. This case demonstrates that chromosomal abnormalities other than the classical t(8;21) can also be associated with granulocytic sarcoma.

Anaplastic large cell lymphoma of true histiocytic origin in an infant: unusual clinical, hematological, and cytogenetic features

We report here the case of a 7-month-old boy who developed anaplastic large cell lymphoma of true histiocytic origin or malignant histiocytosis, with fever, bone and bone marrow infiltration. Usual clinical features were absent. The neoplastic nature of the disease was supported by the presence of clonal chromosomal abnormalities [t(6;8)(p23;p21),der(8)del(8)(q11aq13), der(22) t(11;22) (q13;13)]. Neither B nor T lineage could be demonstrated here. Morphology, ultrastructural analysis, surface antigens expression, and cytogenetics were more specific for the monocyte-macrophage lineage.

[Fetal cardiology: prenatal diagnosis of cardiac malformations]

Foetal cardiology is now a recognised chapter of both paediatric cardiology and foetal medicine. We describe here our experience with antenatal diagnosis of cardiac malformations and discuss both its genetic and epidemiological issues. Our experience confirms if need be that foetal medicine requires a well organised first-level foetal evaluation.

Chromosomal findings in cultured melanocytes from a giant congenital nevus

A giant congenital pigmented nevus was observed in a newborn male. A melanocyte culture was established from nevus fragments removed at age 6 days. Analysis of 136 metaphases harvested from the primary culture showed 74% normal mitoses, 22% polyploids, and 4% mitoses with chromosome rearrangements involving in particular 1p, 12q, and 19p. In addition, the culture showed a high level of HLA-DR expression. Although histology showed no sign of malignancy, these findings may illustrate one of the first events which might eventually progress toward malignancy.

Pyruvate dehydrogenase deficiency: clinical and biochemical diagnosis

A female neonate with pyruvate dehydrogenase (PDH) deficiency is presented with clinical, radiologic, biochemical, neuropathologic, and molecular genetic data. She was dysmorphic, with a high forehead, lowset ears, thin upper lip, upturned nose, and rhizomelic limbs. Cranial MRI revealed severe cortical atrophy, ventricular dilatation, and corpus callosum agenesis. Pyruvate and lactate levels were increased in CSF and blood. Urinary organic acid profile was compatible with PDH deficiency. PDH activity was normal in fibroblasts, lymphocytes, and muscle. The PDH E1-alpha gene was sequenced and a single base mutation was found within the regulatory phosphorylation site in exon 10. It is postulated that this mutation causes a cerebral form of PDH deficiency. Tissue-specific expression of the disease could be explained by differential X chromosome inactivation because the PDH E1-alpha gene is located on this chromosome. Dysmorphism with severe cerebral malformations in female patients merits a metabolic evaluation, including determination of lactate and pyruvate levels in CSF.

Congenital absence of insulin cells in a neonate with diabetes mellitus and mutase-deficient methylmalonic acidaemia

We report on a female neonate with diabetes mellitus and methylmalonic acidaemia, who died at age 16 days. Using immunocytochemistry, electron microscopy and in situ hybridisation, we were unable to demonstrate any insulin cells in the pancreatic islets. Methylmalonic acidaemia was caused by a methylmalonyl coenzyme A mutase apoenzyme defect. The metabolic crisis of the methylmalonic acidaemia aggravated the diabetes and may explain the failure of insulin therapy. Our results suggest that the infant suffered from a congenital absence of beta cells associated with a genetically transmitted mutase apoenzyme defect.

Collaborative study of the molecular epidemiology of Tay-Sachs disease in Europe

Tay-Sachs disease is a lipidosis due to the deficiency of the lysosomal hexosaminidase A. In order to understand the molecular mechanisms of this enzyme deficiency we studied 42 patients of different ethnic origins diagnosed in Europe. The strategy used consists in HEXA cDNA amplification followed by allele-specific oligonucleotide analysis for the frequent mutations, and by chemical cleavage mismatch and denaturing gradient gel electrophoresis for the detection of new mutations. 90% of alleles were clarified in this way, showing a high heterogeneity of HEXA lesions in Tay-Sachs disease. 28 different mutations were found, 20 being identified for the first time in this group of patients.

Deletion of chromosome 11p13-11p15.5 sequences in invasive human ovarian cancer is a subclonal progression factor

In human ovarian cancer, multiple specific chromosomal deletions can be found by cytogenetic analysis or molecular techniques such as restriction fragment length polymorphism probing. This work confirms the loss of HRAS alleles in 1 out of 2 cases of invasive ovarian cancer as determined in 32 samples or cell lines derived from 19 patients. Results with other polymorphic probes indicate that a consensus deletion probably includes 11p15.5-11p13. Tumor suppressor genes might be located in the deleted area, and deletion of the gene might then play a role in disease progression. Examination of DNA from distinct tumor sites of individual patients indicates clonal heterogeneity in the malignant cell population, indicating that loss of 11p sequences is a late event in the disease progression. Loss of alternate 11p alleles at different disease sites in one patient is inconsistent with the current model of tumor suppressor gene inactivation. The 11p deletion seems to be limited to ovarian cancers in younger patients. Eight novel permanent ovarian cancer cell lines, previously not described in the literature and derived from tumor sites from five patients, were included in the current analysis.

Vasopressin and gonadotropin deficiency in a boy with the ectrodactyly-ectodermal dysplasia-clefting syndrome

A boy presented with ectrodactyly (lobster claw deformity), bilateral cleft lip and palate, semilobar holoprosencephaly and microcephaly, associated with congenital hypogonadotropic hypogonadism and central diabetes insipidus. Other aspects of pituitary function were normal. We suggest that the ectrodactyly-ectodermal dysplasia-clefting syndrome can be associated with a variety of hypothalamo-pituitary dysfunctions, in addition to the already described isolated growth hormone deficiency.

Pyruvate dehydrogenase (PDH) deficiency caused by a 21-base pair insertion mutation in the E1 alpha subunit

We report the molecular characterization of a case of a functional PDH-E1 (E1 subunit of pyruvate dehydrogenase) deficiency, a cause of severe congenital lactic acidosis. Residual PDH-E1 activity was reduced to 10% of normal values, although the subunit appeared to be quantitatively and qualitatively normal at the protein level as determined by Western blotting. The sequence of PDH-E1 alpha mRNA and the corresponding genomic DNA revealed an in-frame 21-bp insertion between codons 305 and 306 of the normal E1 alpha cDNA. The mutational insert commences with a novel GAT codon and is a nearly perfect tandem duplication of the wild type DNA sequence. A serine phosphorylation site regulating the activity of the PDH complex is altered by this insertion, which in all likelihood is responsible for the functional enzymatic deficiency leading to lactic acidosis.

Mitochondrial myopathy of childhood associated with depletion of mitochondrial DNA

We have studied five children with mitochondrial myopathy manifesting within or soon after the first year of life. Muscle biopsies showed ragged-red fibers and decreased respiratory chain activity. All five patients had a severe decrease (2 to 34% of normal) in the amount of muscle mitochondrial DNA (mtDNA). The depletion of mtDNA correlated with absence of mtDNA-encoded translation products and with loss of cytochrome c oxidase enzyme activity in individual muscle fibers. This mitochondrial myopathy of childhood illustrates one phenotypic expression of a novel pathogenetic mechanism in mitochondrial diseases, the specific depletion of mtDNA in affected tissues.

Analysis of the peripheral T-cell compartment in the MHC class II deficiency syndrome

To analyse the impact of lack of MHC class II expression on the composition of the peripheral T-cell compartment in man, the expression characteristics of several membrane antigens were examined on peripheral blood lymphocytes (PBL) and cultured T cells derived from an MHC-class-II-deficient patient. No MHC class II expression could be detected on either PBL or activated T cells. Moreover, the expression of MHC class I was reduced both on PBL and in vitro activated T cells compared to the healthy control. However, the reduced expression of CD26 observed on the PBL of the patient was restored after in vitro expansion. Despite the presumably class-II-deficient thymic environment, a distinct but reduced single CD4+ T-cell population was observed in the PBL of the patient. After in vitro expansion, the percentage of CD4+ cells dropped even further, most likely due to a proliferative disadvantage, compared to the single CD8+ T-cell population. However, proliferation analysis showed that T-cell activation via the TcR/CD3 pathway is not affected by the MHC class II deficiency.

Two unrelated children with partial trisomy 1q and monosomy 6p, presenting with the phenotype of the Larsen syndrome

Two unrelated children presented with similar clinical features (facial dysmorphism and multiple joint dislocations) suggesting the diagnosis of Larsen syndrome. Both carried an inherited unbalanced translocation resulting in partial trisomy 1q and partial monosomy 6p. Analysis of skin collagen from one of the probands disclosed a decreased alpha 1/alpha 2 chain ratio of collagen type I, increased thermal stability and increased hydroxylation of proline and lysine. The present findings suggest that, as a result of the chromosome rearrangements, both patients have a mutation on a gene involved in collagen production, located either on chromosome 1q or, more probably, on 6p. It is furthermore suggested that other cases of Larsen syndrome are the result of a similar mutation.

[Cordocentesis: experience in 391 initial samples]

The first diagnostic cordocentesis was performed in our unit in october 1985. Our 4-year experience is reported: 391 cordocentesis were performed in 360 patients during gestational weeks 14 to 42. The first attempt was successful in 90% of the procedures, 4 samplings failed, there were 4 fetal deaths within one week after diagnostic cordocentesis, one of them appears to be directly linked to the punction. A transient fetal bradycardia was observed in 9.9% of the cases, bleeding occurred in 19% of the cases. The indications for cordocentesis were: risk of fetal infection, karyotyping, hemopathy, search for paternity, assessment of fetal acid-base status, biochemical dosage. Our data confirm that cordocentesis is a safe and reliable diagnostic procedure providing guidelines for management of the pregnancy.

[Prenatal diagnosis using amniocentesis and chorionic villi sampling: comparative study of chromosomal findings]

The authors report the results of chromosomal analyses performed on 6235 amniocenteses and 559 choriocenteses. Whereas the frequencies of chromosomal anomalies observed respectively on amniocenteses and choriocenteses did not differ significantly, the comparison of the types of aberrations found revealed, in chorion villi, a relatively high proportion of lethal anomalies, never encountered in amniocyte cultures. Furthermore, chromosomal mosaicism was observed 10 times more frequently on chorion villi than on amniotic cells. These results are globally comparable to those reported in other surveys. In view of literature reports of discordances between fetal chorionic karyotypes, never found in amniocenteses, rapid karyotyping from chorion villi is not as reliable as from amniotic cells. Taking into account the risk of cytogenetic discordance specific to choriocentesis, it is recommended that this method be strictly limited to pregnancies with high genetic risk.