Bloom syndrome is characterized by growth failure, skin anomalies with sun sensitivity, minor anatomic defects, excessive chromosomic fragility and usually severe immune deficiency. The chromosome fragility predisposes these children to the development of hematologic malignancies and solid tumors.Case report. - Morgan, a 4-year-old boy with Bloom syndrome, developed a Wilms tumor. Chemotherapy was poorly tolerated. Two years later, the child died from an uncontrolled progressive disease.Conclusion. - This is the fourth reported case of Wilms tumor occurring in a child with Bloom syndrome. This possibility requires repeated abdominal ultrasonography in such patients.Le syndrome de Bloom associe un retard staturo-ponderal, des anomalies cutanees, une dysmorphie faciale, un deficit immunitaire et une fragilite chromosomique excessive; ce syndrome predispose aux affections malignes.Observation. - Morgan, atteint de ce syndrome, developpe une tumeur de Wilms a 4 ans. Il est traite selon le protocole SIOP 9 mais avec des doses reduites de chimiotherapie en raison d'une mauvaise tolerance (infections). Il decede 2 ans plus tard du non-controle de sa tumeur.Conclusion. - Le nephroblastome s'ajoute a la liste variee des neoplasies associees au syndrome de Bloom, justifiant la surveillance reguliere par echographie abdominale des patients atteints.