This syndrome is characterized by the association of severe hypogammaglobulinemia, combined T and B cell immunodeficiency, absent lymph node germinal centers, absent tissue plasma cells and hepatic veno-occlusive disease. Prevalence at birth is 1/2 500 in the Lebanese population, 25 cases having been described in a 30-year period. Mutations in the gene coding PML nuclear body protein Sp110 were found to be responsible for this association. Transmission is autosomal recessive. Mortality reaches 85% if the syndrome remains unrecognised and untreated.