Alkaline phosphatase activity in neutrophils from patients with severe congenital neutropenia (Kostmann's syndrome)

The glycoprotein alkaline leukocyte phosphatase (ALP) can be used as a mark er of maturity in neutrophilic granulocytes as the activity of ALP increase s during neutrophilic differentiation, Severe congenital neutropenia (SCN) or Kostmann's syndrome is a congenital disorder characterized by a maturati on arrest of myeloid progenitor cells at the promyelocyte/myelocyte stage t hat can be treated with recombinant human granulocyte colony-stimulating fa ctor (rhG-CSF). Until recently there have been no reports on ALP activity i n neutrophils of patients suffering from SCN, despite the fact that ALP is an important correlate of the functional activity of normal neutrophils. Th us. we conducted experiments to assess ALP activity in neutrophils from eig ht SCN patients before initiation of rhG-CSF treatment and an additional 17 SCN patients already receiving rhG-CSF. All eight patients analyzed before initiation of rhG-CSF treatment showed ALP activity in their neutrophilic cells. Four patients had normal and four patients had elevated ALP levels. Of the 17 patients already on treatment with rhG-CSE 15 patients showed ele vated ALP activity levels, one patient had normal ALP levels, and one patie nt showed abnormally low ALP activity. Thus with the exception of a single patient, we observed normal or elevated ALP activity in neutrophils from SC N patients. As described in studies on the effect of rhG-CSF on ALP activit y in healthy individuals, ALP activity was higher in SCN patients already o n treatment with rhG-CSF. Therefore, our results indicate that SCN patients are not deficient in ALP activity and suggest that ALP is not deregulated in the majority of these patients. (C) 1999 The Japanese Society of Hematol ogy.