Objective: To perform a comprehensive characterization of 5 patients with variable degree of congenital mirror movements.

Background: Congenital mirror movements (CMM) are rare non-progressive syndromes with an estimated prevalence of 1 per 1 000 000 individuals; in most cases an underlying heterozygous mutation in the deleted in colon cancer (DCC) gene is found. DCC encodes netrin 1 receptor involved in guidance of commissural axons during embryogenesis. Some heterozygous DCC mutations are also associated with agenesis of the corpus callosum (ACC) while biallelic mutations cause a more severe condition called developmental split-brain syndrome (DSBS).

Method: Clinical exams using the Woods and Teubers scale, transcranial magnetic stimulation, neuroimaging and mass sequencing.

Results: One family (father and daughter) and 3 apparent sporadic cases were examined, with variable degree of mirror movements and describe the novel heterozygous frameshift mutations c.1729delG and c.1466_1476del in DCC. In addition, the c.1466_1476del mutation was associated with a syndrome that include expressive aphasia, seizures and athetosis expanding the spectrum of DCC mutations. This syndrome was responsive to antiepileptic treatment and was associated with ACC also. Despite using WGS we did not identify the underlying mutation in two other cases reflecting genotypic heterogeneity.

Conclusion: Only once have DCC mutations been associated with transient seizures, however athetosis is a new feature. Prognosis for patients with ACC seems to be better than those without mutations in this gene. Work like ours will contribute to establish genotype-phenotype correlations.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/heterozygous-dcc-mutations-more-than-congenital-mirror-movements/