Whether the malignancy is truly related to MRH is debated for several reasons. Most of the reported specific cancer types are reported Because MRH is rare, a reporting bias exists in the literature toward reporting those cases with underlying malignancy, especially previously unreported malignancies. Some of these associations may be a coincidence. The activity of the arthritis and skin lesions of MRH may or may not correlate with the eradication of the cancer, unlike some paraneoplastic disorders where removal of the malignancy may produce improvement in the paraneoplastic findings. Some patients with MRH have been extensively studied or autopsied with no evidence of cancer.
Some patients have thyroid function abnormalities.
Rheumatoid factor is characteristically negative, but has been reported to be positive in at least 4 cases. Occasional patients have had paraproteinemia, cold agglutinins, cryoglobulinemia, or hypergammaglobulinemia. Synovial fluid findings are variable, and reports exist of elevated counts of neutrophils or mononuclear cells. Routine radiographs of joints may be helpful. Bilaterally symmetrical, sharply circumscribed erosions spread from the margins to the joint surfaces.