Wiskott-Aldrich Syndrome in a Girl Caused by Heterozygous WASP Mutation and Extremely Skewed X-Chromosome Inactivation: A Novel Association with Maternal Uniparental Isodisomy 6

Publisher: Karger

E-ISSN: 1661-7819|107|3|185-190

ISSN: 1661-7800

Source: Neonatology, Vol.107, Iss.3, 2015-01, pp. : 185-190

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Abstract

Wiskott-Aldrich syndrome (WAS) is an X-linked disease characterized by microthrombocytopenia, eczema and immune deficiency, caused primarily by mutations in the WASP (Wiskott-Aldrich syndrome protein) gene. Female carriers are usually asymptomatic because of the preferential activation of the normal, nonmutated X-chromosome in their hematopoietic cells. We report our observations of a female child with WAS, who displayed symptoms of congenital thrombocytopenia. DNA sequencing analysis of the WASP gene revealed a heterozygous nonsense mutation in exon 10. The expressions of WASP and normal WASP mRNA were defective. We found preferential inactivation of the X-chromosome on which wild-type WASP was located. Single-nucleotide polymorphism microarray testing and the analysis of the polymorphic variable number of tandem repeat regions revealed maternal uniparental isodisomy of chromosome 6 (UPD6). Our results underscore the importance of WASP evaluation in females with congenital thrombocytopenia and suggest that UPD6 might be related to the pathophysiology of nonrandom X-chromosome inactivation.

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