In the 22 CH patients with positively detected genetic causes, only one patient was associated with the TD-related gene PAX8, while 21 were associated with the TDH-related genes DUOX2, DUOXA2, TG and TPO (Table 1), suggesting that TDH is more common than TD as the major mechanism for CH development. The gene discussed is TPO; the disease is cyclic hematopoiesis.