[Two new cases of X-linked intellectual developmental disorder-105 linked to a previously unreported pathogenic variant in the USP27X gene].

Introduction: X-linked intellectual developmental disorder is clinically and genetically heterogeneous. The ubiquitin specific peptidase 27 X-linked gene (USP27X) has been associated with X-linked intellectual developmental disorder, and only 17 affected males have been described in the literature to date.

Case report: A 6-year-old boy was assessed due to intellectual developmental disability, language delay, behavioural disorder, microcephaly and particular features. His mother had learning difficulties and a facial phenotypic overlap. A maternal uncle had an intellectual developmental disorder. Physical examination revealed an unusual phenotype (triangular facies, long palpebral fissures and eyelashes, medially eyebrow loss, prominent auricles), mild brachydactylia and hypoplasia in the distal phalanges. The clinical exome identified the probably pathogenic variant NM_001145073.3: c.692delT in the USP27X gene. The results of the family segregation analysis were positive: the mother and maternal uncle were harbourers, while healthy maternal aunt was not.

Conclusions: We present two new cases of X-linked intellectual developmental disorder due to a previously unreported variant in the USP27X gene. Both patients presented neurological symptoms without any significant involvement at other levels, according to the literature. One of the cases presented microcephaly, particular features and digital anomalies, which broadens the phenotypic spectrum of this disease.