'Pitted' erythrocytes: impaired formation in splenectomized subjects with congenital spherocytosis.

'Pitted' erythrocyte counts are widely used in the quantitative assessment of functional hyposplenism and in the prediction of recurrence of splenic function in splenectomized subjects. Both of these functions require counts from electively splenectomized controls for comparison. The 'pitted' erythrocyte counts in patients splenectomized for congenital spherocytosis are lower than those found in subjects whose spleens were removed electively for other reasons. This appears to be due to the specific membrane defect which impairs the formation of the vacuoles which are responsible for the appearance of 'pitted' erythrocytes under the interference-phase microscope.