TRANSIENT PANCYTOPENIA PRECEDING ACUTE LYMPHOBLASTIC-LEUKEMIA (PRE-ALL)

Pancytopenia followed by a period of spontaneous recovery may precede the diagnosis of acute lymphoblastic leukemia (pre-ALL). Although both pre-ALL and myelodysplastic syndromes are preleukemic in a strictly t emporal sense, there are several marked differences between the two co nditions. We present eight children with pre-ALL who represented 2% of all cases of childhood ALL. The bone marrow was normo- or hypocellula r with increased reticulin fibrosis during the pre-ALL phase. No cytog enetic abnormalities were found at the pre-ALL phase, but had develope d at the time of overt leukemia in four of the six children examined. Based on the findings in our patients and on cases reported in the lit erature, we argue that pre-ALL is likely to represent a paraneoplastic syndrome early in the leukemic development that might be mediated via inhibitory properties related to clonally expanding but still cytogen etically normal cells. The findings may indicate a multistep pathogene sis of ALL.