Clinical genetics
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The present study evaluated the role of the common lipoprotein lipase (LPL) mutations on the risk of dyslipidemia and coronary atherosclerosis in an Italian population. Cohorts of 632 patients undergoing coronary angiography, as well as 191 healthy controls, were screened by a combination of PCR and restriction enzyme digestion. In the pooled population, the frequencies of LPL D9N and N291S were 4.1%, with no homozygous carriers, whereas that of LPL S447X was 21% with 19.6% heterozygous and 1.4% homozygous carriers. ⋯ No significant influence on plasma lipids by the LPL D9N was observed. None of LPL variants was a significant predictor of angiographically assessed coronary atherosclerosis. At most, the risk was borderline, increased in N291S carriers and possibly decreased in S447X carriers.
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An allele association study of 19 polymorphisms in surfactant proteins SP-A1, SP-A2, SP-B, and SP-D genes in acute respiratory distress syndrome (ARDS) was carried out. Trend-test analysis revealed differences (p < 0.05) in the frequency of alleles for some of the microsatellite markers flanking SP-B, and for one polymorphism (C/T) at nucleotide 1580 [C/T (1580)], within codon 131 (Thr131Ile) of the SP-B gene. The latter determines the presence or absence of a potential N-linked glycosylation site. ⋯ Based on the odds ratio, the C allele may be viewed as a susceptibility factor for ARDS. Although the expression of both C and T alleles occurs in heterozygous individuals, it is currently not known whether these alleles correspond to similar levels of SP-B protein. These data suggest that SP-B or a linked gene contributes to susceptibility to ARDS.
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Anesthesia-induced malignant hyperthermia (MH) is a rare inherited disorder of skeletal muscle. Several mutations in the ryanodine receptor (RYR1) have been found to be causative of MH. The G1021A mutation in the RYR1 is one of the most frequently occurring mutations in European populations. ⋯ This mutation was not found in any of the patients tested. These studies support the absence of this mutation in the normal population. Furthermore, these findings emphasize the importance of viewing the distribution of MH mutations as variable gene pools with frequencies dependent on the geographical location of the population examined.
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Case Reports
Vascular anastomoses leading to amelia and cutis aplasia in a dizygotic twin pregnancy.
Dichorionic placentation is observed in both monozygotic (MZ) and dizygotic (DZ) twinning, while monochorionic placentation is unique to MZ twinning. Examinations of monochorionic twin placentas frequently reveal the presence of vascular anastomoses between the two fetal circulations; such anastomoses rarely occur in dichorionic placentas. ⋯ We report opposite-sex DZ twins in which vascular anastomoses occurred within a fused dichorionic placenta and were associated with vascular disruptions in one twin. The liveborn male twin had amelia, cutis aplasia, and XX/XY blood chimerism; the female twin died in utero.
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The ryanodine receptor 1 (RYR1) mutation C1840T has been reported to segregate with malignant hyperthermia (MH) susceptibility in several families. We have investigated several Scandinavian MH families with respect to five different RYR1 mutations reported to cause predisposition to MH, and we here report on two of the families in which the C1840T mutation was detected. In these two families there was recombination between MH susceptibility and this mutation in one and three individuals, respectively. These findings may suggest that it is necessary to reconsider the specificity of the IVCT and the role of C1840T as a cause of MH susceptibility in some families exhibiting this mutation.