Angie, a 15 yr old female, was admitted to the hospital because of recurrent episodes of pallor, jaundice, and an ulcer on her left leg. Diagnosis of hemolytic anemia had been made at the age of 3 months, and she had been transfused several times since the diagnosis. Physical examination showed jaundice, skeletal growth retardation, and enlargement of the spleen. An analysis of blood showed low Hb content, low RBC count, and elevated reticulocyte count. Morphologic analysis revealed a mixed population of RBCs containing some irregularly contracted cells with irregular surface projections. The life span of the RBCs was found to be severely shortened. Both total and indirect serum bilirubin levels were markedly elevated. Fecal urobilinogen excretion was increased. Biochemical analysis of RBC metabolites showed elevated levels of 2,3 bisphosphoglycerate (2,3 BPG) and reduced levels of ATP. A splenectomy was performed; the spleen showed congestion and the presence of hemosiderin granules. Following splenectomy, there was improvement in both the clinical and hematologic symptoms. An increase in hemoglobin concentration as well as in the number of RBCs and reticulocytes was observed. The biochemical composition of the RBCs did not change after splenectomy

What is the problem with this patient and what is the source of ATP in red blood cells?