Refractory anaemia with excess of blasts as a terminal evolution of paroxysmal nocturnal haemoglobinuria. A case report with chromosomal analysis.

A 63-year-old man presented with paroxysmal nocturnal haemoglobinuria (PNH). After a 31 months' course of typical PNH the patient developed a type 1 (refractory anaemia) myelodysplastic syndrome (MDS) which subsequently evolved into type 5 (refractory anaemia with excess of blasts in transformation) myelodysplastic syndrome. At this time, bone marrow chromosomal analysis revealed a clonal pseudodiploidy (46 XY, -10, -16, -20, +3 markers) while phytohaemagglutinin-stimulated blood lymphocytes had a normal male karyotype. Both the acid haemolysis and thrombin tests remained positive throughout the course of the disease. This case report emphasizes the link between PNH and the myelodysplastic syndromes. Serial chromosomal analysis may help to define the myelodysplastic potential of PNH.