Recently, a new disease of lymphocyte homeostasis caused by somatic mosaicism for the RAS mutation has been discovered (known as RALD, RAS-associated leukoproliferative disorder). Since few cases have been reported in literature, the prognosis and standard treatment for autoimmune diseases associated with RALD remain poorly understood. Standard rituximab therapy (375 mg/m2 for 4 wk) is effective in patients with autoimmune diseases, but early recurrences are common. We highlight the potential for monthly administration of rituximab in a patient with autoimmune thrombocytopenia and hemolytic anemia associated with RALD. RALD was diagnosed in an 11-year-old girl following a 9-year history of severe hepatosplenomegaly and autoimmune cytopenias. Genetic analyses confirmed somatic mosaicism for the G13C KRAS mutation without an autoimmune lymphoproliferative syndrome–related gene mutation. Rituximab therapy was used because of the refractory character of the autoimmune cytopenias which failed to respond to steroids and other immunosuppressive agents. Her treatment consisted of weekly infusions of rituximab for 4 weeks followed by monthly rituximab for 11 months. She maintained her response in hematologic parameters for 2 years after monthly rituximab was ceased and her scores representing quality of life were improved. Rituximab could improve clinical responses and quality of life of the patients with RALD.