ABSTRACT
Objective To screen the mutation of certain gene of a 10-years-old boy with multiple xanthomas and very high level of cholesterol who could be diagnosed as homozygous familial hypercholesterolemia (FH),to explore the relationship between the genotype and phenotype,and to discuss the molecular pathologic mechanism.Methods The basic information of life styles were asked from the boy and his familial members.The blood was drown to examine the lipid and genes.The boy was examined with electrocardiogram examination,ultrasonography and coronary CT angiography (CTA) to evaluate the degree of atherosclerosis.Peripheral blood DNA of the boy and his parents were extracted by phenol-chloroform method and investigated for mutations of promoter and all 18 exons of low density lipoprotein receptor(LDLR) gene.Screening was carried out by using Touch-down polymerase chain reaction (PCR) and single strand conformation polymorphism(PCR-SSCP),combined with DNA sequence analysis.In addition,the apolipoprotein B100 gene(apoB100) for known mutations (R3500Q) which caused familial defective apoB100 was screened by PCR-DNA sequence analysis.Results 1.The level of cholesterol of his parents were higher than the normal.2.Several clinical manifestations of atherosclerosis were detected from that boy.Increased intima-media thickness and plaques were detected in the common carotid artery.Mitral valve regurgitation was found by echocardiography.Coronary stenosis was confirmed by CTA.3.No mutations R3500Q of apoB100 was observed.4.A homozygous mutation in exon13 of the LDLR gene (D601Y) were identified in the boy and his parents harbour D601Y heterozygous mutation due to a single base pair substitution of G for T in the codon for residue 1864.Conclusions The final diagnosis of the boy with multiple xanthomas was homozygous FH.His disease was caused by D601Y homozygous mutation in exon13 of the LDLR gene inherited from his heterozygous parents.
ABSTRACT
Objective To identify mutations site and clinical characteristics of a familial hypercholesterolemia(FH) proband diagnosed clinically through DNA sequencing and family analysis in the proband and his family members of 3 generations.Methods Blood samples and clinical data of the kindred of total 29 from 3 generations members were collected.Proband had a physical examination electrocar-diogrom and vascular ultrasound.The proband and his family members took routine clinical exams,and genomic DNA was isolated.The promoter region and the 18 exons of low density liporotein receptor(LDLR) gene were screened by Touch down polymerase chain reaction -single strand conformation polymorphism(PCR-SSCP) and DNA sequencing.The result of sequencing were matched gene sequence published in the BLAST database.Results 1.Increased intima-media thickness and plaque were detected in the common carotid artery,right subclavian artery of the proband.Aortic valve regurgitation was found by echocardiography.2.No mutation R3500Q of ApoB100 was observed.3.Two heterozygous mutations in exon 10 and 13 of LDLR gene (W462X and A606T) were identified.The proband and 5 members of paternal relatives showed W462X heterozygosis mutation in exon 10 of LDLR gene which introduced the change from tryptophone to a new stop codon.The proband's mother and grandmother harboured A606T heterozygous mutation in exon 13 of LDLR gene due to a single base pair substitution of G for A in the codon for residue 1 879.Conclusions Disease causing mutations of proband are W462X and A606T compound heterozygosis mutation in exon 10 and 13 of LDLR gene inherited from mother and father.Proband shows homozyous phenotype though the genotype analysis indicates heterozygous mutations.