Refractory anaemia and mitochondrial cytopathy in childhood.

We report two cases of childhood myelodysplasia (MDS) related to a mitochondrial (mt) cytopathy that illustrate the difficulty in recognizing such disorders in patients with solely haematological signs. Both patients have refractory anaemia with ring sideroblasts and vacuolization of haemopoietic precursors. These cytological features are similar to those observed in Pearson's disease, recently identified as a mitochondrial disease, and are strongly suggestive of a mitochondrial enzyme defect. The diagnosis of mitochondrial cytopathy was established on Southern blotting of mt DNA, showing a mt DNA deletion, or on the impairment of the respiratory chain enzyme activities. The absence of cytogenic abnormalities, and the polyclonal pattern of peripheral neutrophil and lymphocyte fractions, suggest that, in mt cytopathies, MDS cannot be considered as a truly malignant disorder.