We present the longest known surviving case of a male infant with a mosaic complete trisomy 1q. Born at 39 weeks of gestation with respiratory distress, his weight was 3,330 g (25th centile); he had micrognathia, a posterior cleft of palate, abnormal ears and left thumb, syndactyly, and an absent corpus callosum. Initial blood karyotype was normal (46,XY). He died at age 5 months. Autopsy suggested aspiration as the primary cause of death and confirmed the antemortem findings of an absent corpus callosum and atrial septal defect. It also identified some central nervous system, cardiac, gastrointestinal, and lung anomalies not previously recognized. Cytogenetic analysis of skin fibroblasts obtained at autopsy showed a de novo unbalanced translocation between chromosomes 1 and 22: 46,XY,+1,der(1;22)(q10;q10)/46,XY in the cells examined. The previously reported cases had a similar phenotype with birth weight above the 50th centile for gestational age, small mouth, micrognathia, abnormal ears, abnormal fingers, microphthalmia, and hydrocephalus. The present case and a review of the literature delineates the phenotype in trisomy 1q, and reinforces the critical importance of effective communication between specialists, and obtaining permission for autopsy and skin biopsy, in the pursuit of a diagnosis. © 2009 Wiley-Liss, Inc.