RE: Reactive macrophage activation syndrome (MAS) in a patient with parvovirus B19 infection, lymphocytic lichenoid vasculitis, urticaria and angioedema.

To the Editor: I read with keen interest the article published by Soldo-Juresa et al in the last issue of the journal.1 I would like to make some comments: First, Still disease should be kept in mind whenever macrophage activation syndrome is considered in a patient with the clinical picture shown. In fact the patient's condition fulfills the criteria published by Yamagushi for Still disease.2 I would like to remark that the measurement of soluble IL-2R (also known as CD25s) could be helpful in distinguishing between Still disease and MAS.3 Furthermore, the development of MAS in Still disease is not infrequent and intravenous gamma globulins have shown promising results in treatment.45 Second, as the authors rule out a C1q-linked vasculitis, C4 and alternative complement pathway activity should be measured. It is well known that in esterase inhibitor type II levels of C1-inhibitor esterase are normal although C4 is decreased due to low functional C1-inhibitor levels.6 Hypocomplementemic vasculitis has been also described in patients with factor I deficiency.7 I have attended recently a patient with vasculitis secondary to factor I deficiency. This factor was not measured by the author in this patient. Third, the authors recognize that DNA of parvovirus B-19 can persist in bone marrow for years. This is why we should distinguish between MAS secondary to viral infection or underlying Still disease that needs long-term treatment and follow-up.