Introduction: Co-existence pathogenic copy number variation with aneuploidy is a rare phenomenon. Whole TBL1XR1 gene deletions are described and associated with autosomal dominant intellectual development disorder-41 (#616944). However, the phenotypical expression of the TBL1XR1 partial deletion is poorly described. Case Presentation: We describe the case of a male, aged 18 months, who presented delayed motor development, gait disturbance, mild generalized hypotonia, minor dysmorphic features, and growth failure, in addition to Klinefelter syndrome (KS). The single nucleotide polymorphism array revealed the de novo pathogenic interstitial deletion of chromosome 3q26.32 of 202 kb size that encompassed the first two exons of one relevant coding gene: TBL1XR1 (*608,628). Conclusion: We report a male without clinical signs of KS and overlapped phenotypical features with another TBL1XR1-related disease: Pierpont syndrome (#602342). This patient extends the phenotypic spectrum of TBL1XR1 gene pathogenic variants.

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