ABSTRACT
Omenn syndrome is a variant of combined severe immunodeficiency due to mutations in RAG genes. It is characterized by polymorph symptoms and lethal outcome. We report on two cases of Omenn syndrome. Infants were aged 50 and 46 days. The clinical and biological signs were typical and complete in the first case. In the second case, only the cutaneous signs were present. Diagnosis was confirmed by genetic study. The Rag1 T631 mutation was found in these two patients. Hematopoietic stem cell transplantation could not be done and the evolution was fatal in both cases because of severe infectious episodes. Prenatal diagnosis was performed in the two families and each family has currently a healthy child. In conclusion, early diagnosis of Omenn syndrome may avoid infectious complications responsible for delay in therapeutic management. Genetic study confirms the diagnosis. The treatment usually consists of hematopoietic stem cell transplantation in association with immunosuppressive drugs. Prenatal diagnosis is very important to allow parents to have healthy children.