Cytophagic histiocytic panniculitis: is it a macrophage activation syndrome in situ?

Patients A 10-month-old year boy and a 4-month-old-year girl presented with multiple erythematous and indurated noduless on the limbs, and developed high-grade fever and biological features suggestive of MAS several months after the onset of cutaneous disease. Serologic test for EBV was negative and bone marrow examination revealed hemophagocytosis. A homozygous splicing mutation for the UNC13D gene encoding for Munc 13-4 was present in patient 1, but NK cell cytotoxicity and degranulation assays, and expression of Munc 13-4 protein were normal. No mutation was found in Patient 2. Prednisone alone failed to induce a sustained remission which was obtained by adding cyclosporine A.