Abstract
Macrophage activation syndrome（MAS）has been observed in patients with systemic lupus erythematosus（
SLE）．Recognition of MAS in patients with SLE may be particularly challenging because it may mimic
the clinical features of the underlying disease or be confused with an infectious complication． We present a case
of SLE associated MAS（SLE-MAS）． The patient showed the distinct cytokine profile of SLE-MAS compared
to systemic juvenile idiopathic arthritis associated MAS． The observed TNF-α dominant increase appears
to be characteristic of SLE-MAS．IgM type antilymphocyte antibody（ALAB）was detected on the surface
of lymphocytes during the acute phase and disappeared when the patient was in remission． The patient had a
heterozygous P369S-R408Q mutation in the MEFV gene． Our results suggest that ALAB and a MEFV mutation
might play important roles in the pathogenesis of SLE-MAS． Furthermore，the cytokine profile of SLE-MAS
differs from that of S-JIA-MAS：the TNF-α dominant increase appears to be characteristic．
