【Abstract】 Objective The diagnosis and treatment of idiopathic pulmonary iron-written hemosiderosis (IPH) in children remains unsatisfactory, and the aim of this clinical study was to summarize the diagnosis of IPH and to assess the long-term efficacy of dose-individualized mercaptopurine (6MP) for the treatment of IPH. METHODS The diagnosis of IPH was established by hospitalization for examination and follow-up for more than 1 year to exclude other diseases. Prednisone was administered orally at 2 mg/(kg.d) during the acute phase of the disease, which was tapered off at 4 weeks, and 6MP was initiated orally at the same time at 60 mg/(m2.d), with maintenance therapy for 3 years. A total of 15 children, aged 2-13 years (median 7 years) at the time of diagnosis, met the diagnosis and were included in the analysis. Most of the children were delayed in diagnosis due to atypical onset of symptoms, with a delay of 0-108 months (median 8 months). All cases resolved with treatment and were successfully withdrawn from hormones. At a follow-up of 2.5 to 9.5 years (median 6 years), only 1 of 8 patients with relative hypoleukinemia (3×109/L to 6×109/L) during 6MP maintenance therapy relapsed, compared with 5 of the other 7 (p<0.05). Four of the five latter relapses did not recur after the 6MP dose was adjusted upward to bring down the leukocytes. Conclusion Delay in diagnosis remains a prominent problem. Most of the children with IPH in this group tolerated 6MP maintenance therapy well and achieved long-term remission, suggesting that it is possible to avoid long-term reliance on hormone therapy and the resulting long-term adverse effects on growth and development; 6MP metabolism varies widely among individuals, and dose individualization may help to avoid under- or over-treatment in some cases, which may help to improve the prognosis, and the leukocyte counts may be a simple and useful indicator.