VEXAS, Chediak-Higashi syndrome and Danon disease: myeloid cell endo-lysosomal pathway dysfunction as a common denominator?

Vacuolization of hematopoietic precursors cells is a common future of several otherwise non-related clinical settings such as VEXAS, Chediak-Higashi syndrome and Danon disease. Although these disorders have a priori nothing to do with one other from a clinical point of view, all share abnormal vacuolization in different cell types including cells of the erythroid/myeloid lineage that is likely the consequence of moderate to drastic dysfunctions in the ubiquitin proteasome system and/or the endo-lysosomal pathway. Indeed, the genes affected in these three diseases UBA1, LYST or LAMP2 are known to be direct or indirect regulators of lysosome trafficking and function and/or of different modes of autophagy. Furthermore, all three genes are highly expressed in the more mature myeloid cells pointing out their likely important function in these cells. LAMP2 deficiency for instance is known to be associated with alterations of lysosome architecture and function. It is thus well established that different cell types from Danon disease patients that harbor invalidating mutations in LAMP2 exhibit giant lysosomes containing undigested materials characteristic of defects in the fusion of lysosomes with autophagosomes, a feature also found in VEXAS and CHS. Other similarities regarding these three diseases include granulocyte and monocyte dysfunctions and a recurrent inflammatory climate. In the present review we discuss the possibility that some common clinical manifestations of these diseases, notably the hematopoietic ones are consecutive to a dysfunction of the endo-lysosomal pathway in myeloid/erythroid progenitors and in mature myeloid cells including neutrophiles, monocytes and macrophages. Finally, we propose reacidification as a way of reinducing lysosome functionalities and autophagy as a potential approach for a better management of these diseases.