Spectrum of Molecular Defects and Mutation Detection Rate in Patients with Mild and Moderate Hemophilia A

Abstract

Communicated by Arupa GangulyThe amount of residual F8 (FVIII:C) determines the clinical severity of hemophilia A. Recently, we showed that the mutation detection rate in severely affected male patients (FVIII:Co1% of normal) is virtually 100% when testing for the common intron 22-/intron 1-inversions and big deletions, followed by genomic sequencing of the F8 gene. Here we report on the spectrum of mutations and their distribution throughout the F8 gene sequence in 135 patients with moderate (n 5 23) or mild (n 5 112) hemophilia A. In contrast to the severe form of the disorder, analysis on the genomic level failed to detect the molecular defect in 4% of the moderately and in 12% of the mildly affected patients. A total of 36 of the mutations identified in this study are novel. The vast majority of the detected changes were missense. The newly detected amino acid substitutions were scored for potential distant or local conformational changes and influence on molecular stability for every single F8 domain with available structures, using homology modeling. Two molecular changes in the promoter region of the factor VIII gene (c.-112G4A and -219C4T), affecting the core segment (minimal promoter) were detected in two patients with mild hemophilia A. To our knowledge this is the first report on promoter mutations in the F8 gene. Hum Mutat 28(1), [54][55][56][57][58][59][60] 2007.

Molecular and phenotypic determinants of the response to desmopressin in adult patients with mild hemophilia A

“…In keeping with a recent report [24], we detected mutations in 82% of mild hemophilia patients, a figure substantially lower than that reported for patients with severe hemophilia A [14]. Several factors may explain this lower efficiency, such as unrecognized type 2N VWD, which however was excluded in our patients, the presence of deep intronic F8 mutations or the effect of genes other than F8 in reducing FVIII.…”

Characterization of a novel mutation in the F8 promoter region associated with mild hemophilia A and resistance to DDAVP therapy

“…Mutations in the F8 promoter region have been described only rarely [1,5] and, to our knowledge, the mutation found in this family has not been previously reported. Interestingly, polymorphisms in the F8 promoter region have been recently found to influence FVIII synthesis.…”

Análisis de las inversiones del intrón 1 y 22 y secuenciación del gen F8 para el diagnóstico genético-molecular de hemofilia A en Chile

“…El costo, aun cuando ha disminuido, es un aspecto a considerar al realizar secuenciación para el estudio de genes tan grandes como el gen F8, en los que las mutaciones se pueden encontrar a través de todo el gen. Una alternativa que puede ayudar a optimizar los costos, es realizar el análisis por etapas de acuerdo a la frecuencia con que se presenten las alteraciones en cada población y también al fenotipo, tal como se ha propuesto en otros trabajos 17 . De esta manera, en pacientes con hemofi lia A severa se podría comenzar con el estudio de la inversión del intrón 22 y del intrón 1, y continuar con la secuenciación del exón 14, en el que, de acuerdo a lo reportado en el sitio HAMSTeRS, se encuentran con frecuencia mutaciones en pacientes con este fenotipo.…”