RESUMEN
La trombocitopenia como motivo de consulta, requiere la búsqueda intencionada de orientar manifestaciones extrahematológicas. La megacariogénesis pasa por distintas etapas dependientes de la interacción de varios genes, entre ellos el MYH9, cuya expresión permite una adecuada formación y migración de las proplaquetas al ser liberadas al torrente sanguíneo, al mismo tiempo, existen estructuras con fisiología similar a nivel de citoesqueleto (podocitos, cilios cocleares, etc.) que podrían vincular a datos de pérdida de audición, enfermedad renal, cataratas y elevación de enzimas hepáticas conllevando a una enfermedad relacionada al gen MYH9. Se presenta el caso de un adolescente, de sexo masculino, con trombocitopenia recurrente, con el antecedente de padre con coagulopatía inespecífica, pérdida de audición, falla renal crónica, quien falleció a los 34 años por hemorragia intraparenquimatosa y edema cerebral severo, en quien se identifica una variante patogénica en heterocigosis en el gen MYH9, poniendo en relevancia la expresividad variable y efectos pleiotrópicos de este gen.
Thrombocytopenia as a reason for consultation requires an intense search to guide extrahematological manifestations. Megakaryogenesis goes through different stages depending on the interaction of several genes, including MYH9, whose expression allows proper formation and migration of proplatelets when released into the bloodstream, at the same time, there are structures with similar physiology at the cytoskeleton level (podocytes, cochlear cilia, etc.) that could be linked to data on hearing loss, kidney disease, cataracts and elevated liver enzymes leading to a disease related to the MYH9 gene. We present the case of an adolescent, male, with recurrent thrombocytopenia, with a history of a father with nonspecific coagulopathy, hearing loss, chronic kidney failure, who died at the age of 34 due to intraparenchymal hemorrhage and severe cerebral edema, in whom identifies a heterozygous pathogenic variant in the MYH9 gene, highlighting the variable expressivity and pleiotropic effects of this gene.
Asunto(s)
TrombocitopeniaRESUMEN
We studied a family presenting 10 individuals affected by autosomal dominant deafness in all frequencies and three individuals affected by high frequency hearing loss. Genomic scanning using the 50k Affymetrix microarray technology yielded a Lod Score of 2.1 in chromosome 14 and a Lod Score of 1.9 in chromosome 22. Mapping refinement using microsatellites placed the chromosome 14 candidate region between markers D14S288 and D14S276 (8.85 cM) and the chromosome 22 near marker D22S283. Exome sequencing identified two candidate variants to explain hearing loss in chromosome 14 [PTGDR - c.G894A:p.R298R and PTGER2 - c.T247G:p.C83G], and one in chromosome 22 [MYH9, c.G2114A:p.R705H]. Pedigree segregation analysis allowed exclusion of the PTGDR and PTGER2 variants as the cause of deafness. However, the MYH9 variant segregated with the phenotype in all affected members, except the three individuals with different phenotype. This gene has been previously described as mutated in autosomal dominant hereditary hearing loss and corresponds to DFNA17. The mutation identified in our study is the same described in the prior report. Thus, although linkage studies suggested a candidate gene in chromosome 14, we concluded that the mutation in chromosome 22 better explains the hearing loss phenotype in the Brazilian family.