OBJECTIVE: We investigated mortality and long-term development of malignant hematological disease, cancer, liver-, renal-, and rheumatic disease in patients with unexplained cytopenia (UC).

METHODS: We screened all patients referred to the outpatient clinic at the Department of Hematology, Rigshospitalet, Copenhagen, with a suspected myeloid neoplasm from June 2009 to the end of 2012. Through registry linkage, we obtained information on hospital-based ICD-10 diagnoses and survival. We estimated cumulative incidences of disease and hazard ratios of all-cause mortality using the Aalen-Johansen estimator and Cox regression. We compared incidences and mortality with a control cohort.

RESULTS: Among 1820 referrals, 221 had UC. The UC group had a 5-year cumulative incidence of malignant hematological disease of 8.91% (CI 95%: 4.98-12.84) compared to 0.93(CI 95%: 0.32-1.55) in the matched controls. In addition, UC patients had higher incidences of cancer, liver, and rheumatic disease. Mortality was higher in UC patients compared to the matched controls with a HR of 1.43 [P = 0.038, CI 95%: 1.02-2.00] adjusted for comorbidity, sex, and age. Most of the mortality and morbidity were ascribed to patients 50 years or older.

CONCLUSIONS: Unexplained cytopenia patients had a higher incidence of malignant hematological-, cancer-, liver-, and rheumatic disease and increased mortality compared to the general population.