The most frequently mutated genes within each subtype were as follows: PCLO (27%), POT1 (27%), and STAT3 (27%) in idiopathic PRCA; STAT3 (20%), DNMT3A (10%), and CUX1 (10%) in thymoma-associated PRCA; and STAT3 (54%) and TET2 (12%) in LGLL-associated PRCA. The gene discussed is CUX1; the disease is pure red-cell aplasia.