SEVERE COMBINED IMMUNODEFICIENCY (SCID) ASSOCIATED NEUTROPENIA - A LESSON FROM MONOZYGOTIC TWINS

A case of severe combined immunodeficiency (SCID) in monozygotic twin sisters was detected at 3 months of age with neutropenia in one twin a nd a normal differential count in the other. The neutropenic twin, suf fering from severe skin ulcers, was successfully treated with granuloc yte colony stimulating factor (G-CSF). Discordant occurrence of neutro penia in identical twins shows that there may be a non-genetic cause f or the in SCID. Suppression of was probably induced by activated mater nal T cells. The neutropenia in this case may thus be classified as SC ID associated neutropenia, as opposed to reticular dysgenesis, in whic h the neutropenia is G-CSF refractory and is most probably caused by a genetic stem cell defect. A response to G-CSF in a neutropenic child with SCID can be clinically beneficial and might help to distinguish b etween G-CSF unresponsive reticular dysgenesis and G-CSF responsive SC ID associated neutropenia.