Summary

The authors report two cases of morning granulocytopenia: a 73-year-old female with a long-standing, active rheumatoid arthritis (RA) and a non-tuberculous mycobacteria (Mycobacterium avium) pulmonary infection, and a 55-year-old female with longstanding systemic lupus erythematosus (SLE). After admission, the patients’ peripheral neutrophil counts decreased with no associated symptoms. In both cases, The authors identified diurnal variation in peripheral blood neutrophil counts in blood samples collected at 3-h intervals. The white cell count (WCC) in the first case rose from 2500 cells/μl (neutrophils: 1512 cells/μl) at 08:00 to 6100 cells/μl (neutrophils: 5185 cells/μl) at 14:00, and from 2200 cells/μl (neutrophils: 319 cells/μl) at 06:00 to 2900 cells/μl (neutrophils: 2291 cells/μl) at 12:00 in the second case.

These cases are educational because necessary treatments would be stopped when morning granulocytopenia is not recognised. Morning granulocytopenia should be noted in the differential diagnosis in cases of incidentally found, asymptomatic granulocytopenia.