Reticulocytosis: defective reticulin degradation, a case report

In summary, this case illustrates a previously unrecognized syndrome of reticulocytosis secondary to a defect in reticulin degradation. We are aware of two other case reports in the literature which also describe patients with an elevated reticulocyte count who's red cells appeared to lack the ability to degrade reticulin (Lofters et. al.1978, Tulliez et. al. 1982). Both of these cases however, demonstrated only mild reticulocytosis and appeared to be related to preleukemic syndromes. Our patient had no evidence of preleukemia and indeed, has been followed for over four years without evidence of other hematologic abnormalities. The mild anemia that has persisted in this patient may suggest that although no evidence of hemolysis is obvious in this patient, some minor amount of hemolysis may be occurring. Due to the relative insensitivity of other measures of early red cell death (51Cr survival, bone marrow biopsy, etc...), and the loss of the the reticulocyte count as a sensitive index of hemolysis, a minor amount of hemolysis cannot be excluded. This does not decrease the validity of the observations noted above, since this massive reticulocytosis cannot be explained by minimal hemolysis. Whether this patient's reticulocytosis represents an acquired or congenital syndrome is unsettled at present. Although his brother is unaffected, and we have on record only a mildly elevated reticulocyte count from 1981, there remains a possibility that this syndrome is congenital. We are, at present, in the process of further characterizing the specific defect in these red cells. Further assays of Lipoxygenase and protease activity, the ability to ubiquitinate proteins, specific identification of the mitochondria-like structures, and protein synthesis assays are in progress or are planned. The inability to degrade reticulin in this patient's red cells and the impact of this upon other cellular physiologic processes afford an excellent opportunity to enhance our understanding of normal red cell physiology, particularly, we suspect in this patient, of Ubiquitin-ATP-dependent proteolysis.