Constitutional trisomy 8 mosaicism (46,XX/47,XX,+8 or 46,XY/47,XY,+8) is characterized by trisomic distribution of chromosomes in some but not all cells of the body. The full condition presents with physical stigmata, skeletal abnormalities and a mild to moderate cognitive impairment.Here we present a boy aged 3 years 10 months with partial trisomy 8 who was referred because of a language impairment. Because of known anomalies (corpus callous agenesis, deformities of the spine) a chromosomal analysis was initiated.This case highlights the necessity for an interdisciplinary diagnostic approach in children with language impairment and other constitutional disorders.