Pitfalls in the diagnosis of autoantibodies associated with paraneoplastic neurologic disease.

We studied the sera of 15 patients with Sjögren's syndrome using the Western blot technique for the presence of anti-Ro and anti-Hu (type 1 antineuronal nuclear autoantibody [ANNA-1]). All sera reacted with Ro-52 protein. Two of the Sjögren sera reacted with 38-kd bands on Western blots of rat cerebellar homogenate, resembling anti-Hu immunoreactivity. However, when reacted with purified human Purkinje cells or purified recombinant HuD protein, none of the sera immunoreacted with the Hu antigens. We recommend the use of either a recombinant Hu protein or the combination of immunohistochemistry and Western blot of purified human neuronal preparations to identify paraneoplastic antibodies. This approach will prevent the unnecessary workup for suspected lung cancer.