Normal fluctuations of leucocyte counts and the response to infection in benign familial leucopenia

In a long-term follow-up of 47 Yemenite patients with benign familial leucopenia, the mean white-cell count was 4, 578 with a standard deviation of 940. During bacterial infections, the average leucocyte increment was the same in leu-copenic as in non-leucopenic subjects, leading to total leucocyte counts in the normal range in previously leucopenic subjects. The marked degree of variability makes clinical interpretation difficult when leucocyte counts are found between levels standardised as normal in sick patients previously known to be leucopenic.