Myelodysplastic syndrome (MDS) is a heterogenous group of stem cell disorders usually characterized by progressive refractory cytopenias, which could progress to acute myeloid leukemia. MDS may be associated with a wide spectrum of skin lesions, including neoplastic cell infiltration, Sweet's syndrome, pyoderma gangrenosum, erythema elevatum diutinum, vasculitis, and panniculitis. However, erythema nodosum is rarely associated with MDS. Unusual rheumatologic manifestations in patients with MDS also have been reported, which range from asymptomatic serological abnormalities to classic connective tissue disorders such as Sjögren's syndrome, relapsing polychondritis, systemic lupus erythematosus, rheumatoid arthritis and mixed connective tissue disease. However, concurrent erythema nodosum and serositis has rarely been reported. We describe a case of MDS with erythema nodosum and immune-mediated pericardial effusion in a 34-year-old woman.