Werdnig-Hoffmann disease. First prenatal diagnosis in Cuba
Introduction. Spinal muscular atrophy (SMA) is an autosomal recessive disorder characterized by the degeneration of cells of the spinal cord. The gene was localized on chromosome 5q13 and exists in two almost identical forms, which are distinguished by the change of base on exones 7 and 8. Mutations of the gene of survival motoreneuron (SMN) are the cause of illness. Clinical case. We report, for the first time in Cuba, the prenatal diagnosis of a type II SMA carrier, using molecular methods for direct detection of the mutation on exones 7 and 8 of the SMN gene, and haplo-identification with microsatellite markers of chromosome 5q as an indirect method. A sample of amniotic liquid was taken at 18 weeks of gestation and the DNA extracted. No deletions were detected on exones 7 and 8 of the foetal DNA, which was therefore normal. Conclusions. Detection of deletions on the SMN gene is a method which permits detection of the condition (healthy or unhealthy) of the foetus, quickly and reliably, without requiring investigation of the entire family to obtain a result. The method does not require radio-active PCR, the results are clear and precise and may be obtained within 24 hours. It may also take the place of invasive methods such as muscle biopsy and electro-myography and contribute to genetic assessment in families in which there is no DNA of the affected child.
Caso clínico Presentamos, por primera vez en Cuba, el diagnóstico prenatal en una portadora de AME tipo II, utilizando métodos moleculares de detección directa de la mutación en los exones 7 y 8 del gen SMN, y la haploidentificación con marcadores microsatélites del cromosoma 5q como método indirecto. Se tomó la muestra de líquido amniótico a las 18 semanas de gestación y se extrajo el ADN. No se detectaron deleciones de los exones 7 y 8 en el ADN del feto, por lo tanto es sano.
Conclusiones La detección de deleciones en el gen SMN es un método que permite llegar a conocer la condición (sano o enfermo) del feto, con seguridad y en menor tiempo, sin necesidad de investigar a toda la familia para llegar a un resultado. Este método no necesita PCR radioactivo, los resultados son claros y precisos, y pueden obtenerse en un día; además, puede llegar a sustituir a los métodos invasivos tales como la biopsia de músculo y la electromiografía, y ayudar al asesoramiento genético en aquellas familias donde no existe ADN del niño afectado
