A mixed prospective and retrospective study by Flores14 reported a positive response to IVIG in 29 of 73 patients (39.7%), including 6 out of 11 children (54%), with two variables strongly associated with a good response: the presence of hepatomegaly with or without splenomegaly and a low pretreatment Hb. The gene discussed is GSTM1; the disease is Hepatomegaly.