Tetrasomy X and neuropathy: double trouble or extended phenotype?

Introduction: The tetrasomy X is a rare chromosomal aberration with a highly variable phenotype, caused by an insufficient inactivation of supernumerary X chromosomes. X tetrasomy in combination with a neuropathy has not been described so far.

Case report: Initial presentation with an 11-year-old child because of a language impairment and paresthesia. The physical examination showed pes cavus, mild facial abnormalities, clinodactyly of Dig.V li> re and muscular hypotonia. Neurophysiologically decreased motor nerve conduction velocity of peroneus and tibial nerve. In addition, good hearing, a slight mental disability, aplasia of the left kidney and left ovary. Endocrinological examinations, kidney function, cranial MRI, muscle and nerve biopsy, echo, and ECG were normal.

A CGH array showed a strong enrichment in the region of the X chromosome. The chromosome analysis confirmed tetrasomy X

Conclusion: The tetrasomy X is rarely described. The probability of a failed complete inactivation increases with the number of the X-chromosomes. Therefore, on specific neurological findings, in combination with a retardation, a chromosome analysis should be performed