# Neurodevelopmental Profile of a 4.5-Year-Old Girl with Tetrasomy X

## TL;DR

This case study explores the neurodevelopmental profile of a young girl with Tetrasomy X, highlighting the variability in her development and the importance of early intervention.

## Contribution

The study identifies global sensory under-responsiveness as a novel feature in Tetrasomy X and emphasizes the need for individualized assessments.

## Key findings

- The girl showed borderline intellectual functioning and mild global developmental delay.
- Sensory processing revealed global under-responsiveness, a previously underreported feature in Tetrasomy X.

## Abstract

Background: Tetrasomy X (48, XXXX) is an extremely rare sex chromosome aneuploidy characterized by highly variable phenotypic manifestations. It includes various medical issues, a wide range of developmental delays, and neurocognitive deficits. Methods: The present case report provides a comprehensive neurodevelopmental profile of a 4.5-year-old girl with Tetrasomy X, with the aim of contributing to phenotype delineation, exploring genotype–phenotype associations, and emphasizing the importance of early, targeted intervention. A multidisciplinary assessment was conducted, encompassing cognitive, speech–language, motor, sensory, adaptive, and socioemotional functioning, using a battery of standardized and culturally adapted instruments. Results: Results revealed borderline intellectual functioning and mild global developmental delay, with marked intra-individual variability across domains. Motor development was significantly delayed and speech and language assessment demonstrated a pronounced receptive–expressive discrepancy. Sensory processing evaluation revealed a pattern of global sensory under-responsiveness, representing a novel and underreported feature in Tetrasomy X. Adaptive functioning was uneven, with relative strengths in daily living skills and weaknesses in motor abilities. Conclusions: This detailed early developmental characterization highlights the heterogeneity of Tetrasomy X and challenges some of the previous assumptions. The findings underscore the necessity of individualized, multidisciplinary assessment and early intervention to optimize developmental outcomes and quality of life in affected individuals.