The Philadelphia Chromosome in an Unusual Case of Myeloproliferative Disease

In an unusual case of myeloproliferative disease, the Ph¹ chromosome was found in association with persistently elevated levels of LAP activity. Clinical findings in this case included marked thrombocytosis, basophilocytosis, absence of splenomegaly and a preceding history of untreated ankylosing spondylitis. Cytogenetic findings were compatible with the existence of the Ph¹ chromosome in erythroid and megakaryocytic as well as granulocytic marrow precursors.

This case illustrates the difficulties currently encountered in the clinical differentiation of myeloproliferative disorders and in interpreting the diagnostic significance of the Ph¹ chromosome. The co-existence in this case of the Ph¹ chromosome and elevated LAP does not support the concept of a direct relationship between Group G chromosomes and LAP activity.