[Combined deficiency of factors V and VIII caused by a novel compound heterozygous mutation of gene Lman1].

Combined deficiency of factor V and VIII (F5F8D) is a rare, autosomal recessive disorder caused by mutations of either lman1 or mcfd2. To identify mutations of these two genes in a Chinese F5F8D family, the samples of peripheral blood were collected from the proband and her parents. Coagulation tests were carried out, including activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), fibrinogen (Fg) and coagulate activity of FV, FVIII (FV:C, FVIII:C). The genomic DNA was extracted, then all the exons and intron/exon boundaries of these two genes were amplified by polymerase chain reaction (PCR). The products were finally analyzed by direct sequencing. The results showed that the proband's APTT, PT, TT, Fg, FV:C and FVIII:C were 82.2 sec, 19.6 sec, 18.6 sec, 2.9 g/L, 7.1% and 18.7% respectively, while those parameters of the parents were all within the normal range. Two pathogenic mutations were identified in lman1 gene of the proband: one was the heterozygous c.912_913insA in exon 8 resulting in a frameshift of p.Glu305fsX20; the other was the heterozygous c.1366C > T in exon 11 resulting in p.Arg456X. The proband's father and mother were heterozygous for c.1366C > T and c.912_913insA respectively. It is concluded that F5F8D of the proband is caused by a novel compound heterozygous mutation of the lman1 gene, which has never been reported.