[Rett syndrome. Classical form and preserved speech variant as a different phenotype effect of deletion with the same starting point in MeCP2 gene - report of 2 cases].

BACKGROUND

Rett syndrome is a common cause of mental retardation in girls. Characteristic features of RS include: profound impairment of cognitive abilities, impaired communication skills, stereotypic movements, seizures, respiratory disorders, dystonia. Classical Rett syndrome as well as variants such as forme fruste and variant with preserved speech were observed. Mutation in the MeCP2 gene is found in about 90% of RS.

OBJECTIVE

This paper describes two cases of Rett syndrome (RS) caused by the presence of different size deletion in the MeCP2 gene.

MATERIALS AND METHODS

DNA was isolated from peripheral blood lymphocytes of two patients: 2.5 years-old and 12 years-old, in whom Rett syndrome was suspected. For this study, PCR-RFLP method and sequencing were used.

RESULTS

Patient 1 had a deletion of 35 nucleotides: del35 nt c.1159-1193 in one allele of the MeCP2 gene. Patient 2 had a deletion of 44 nucleotides in one allele of the MeCP2 gene del44 nt c.1159-1202. Both described girls with Rett syndrome had a deletion leading to frameshift at the C-terminal region of the MeCP2 gene, which begins at the same point (c.1159), but, the phenotypes are different. The patient with a smaller deletion of 35 nucleotides has the classical form of RS, the second patient with a deletion of 44 nucleotides has a variant with preserved speech.

CONCLUSIONS

There is a significant phenotypic variation in Rett syndrome associated with deletions of the C-terminal region of the MeCP2 gene and it only partly depends on the location and type of mutation. Presumably, other mechanisms, such as non-random X chromosome inactivation and/or the effect of interaction between different genes may play an important role in shaping the phenotype in Rett syndrome.