Objective: We report on 3 cases with complex clinical phenotypes and unreported mutations detected at sequencing, which raise difficulties in interpretation.

Cases presentation: First case is a 3 years-old boy with epileptic seizures, macrocephaly and psychomotor regression, and MRI suggestive for Alexander disease (diffuse demyelization in fronto-insular white matter and striate nucleus bilaterally, with progressive aspect). Sequencing of GFAP gene was indicated. The second case is a 7 years-old with epilepsy and developmental delay. In this case a panel of 150 genes for epilepsy has been sequenced by next generation sequencing (NGS). The third case is a 2 years-old girl with global developmental delay and ataxia. Whole exome sequencing was performed in this case.

Results: The genetic testing revealed: in the first case, a heterozygous variant in exon 1 of the GFAP gene, c.292G>C, previously unreported, which was interpreted as being of uncertain significance; in the second case, 2 mutations, in heterozygous state, on SLC2A1 gene, c.1176C>T, reported as pathogenic, and c.998G>A, considered as unclassified variant of undetermined pathogenicity; in the third case, a previously unreported heterozygous variant in the CACNA1A gene, c.2122G>A.

Conclusions: In these cases, gene sequencing could not bring a clear clinical interpretation, although variants in genes relevant for their respective phenotypes were identified. New data (genetic testing of the parents, other cases with similar variant, functional studies) could bring further information about the clinical impact of these variants of uncertain significance.