Two women with the rare association of systemic lupus erythematosus (S
LE) and myasthenia gravis (MG) are reported. The first patient develop
ed SLE (arthritis, severe thrombocytopenia, and high titres of anti-DN
A antibodies) 6 years following successful therapeutic thymectomy for
MG. The second patient developed SLE (oral ulcers, arthritis, serositi
s, leukopenia, high titres of anti-DNA and anti-nuclear antibodies) 4
years prior to the clinical and serological onset of MG. Lymphocyte su
bsets and in vitro proliferative responses of peripheral blood mononuc
lear cells to mitogens were normal in both patients. A review of the l
iterature revealed 26 additional patients with definite SLE coexisting
with MG. Besides the theoretical interest of this association, the di
fferential diagnosis of fatigue in patients with SLE should always inc
lude the possibility of MG.