EPO and anemia: However, hemoglobin and reticulocyte count remained low for several months, even under combined substitution of erythropoietin, iron and vitamin C. Considering the widespread expression of the transcription factor GLIS3 among different organs and progenitor cell populations (27) as well as findings on persistent fetal hemoglobin levels detected in two earlier reported children with GLIS3 mutations (4, 5), it is possible that the transient hyporegenerative anemia may represent a further symptom related to the GLIS3 defect.