LEMS Patient Positive for Cancer Marker, But Shows No Sign of Tumor
A woman with Lambert-Eaton myasthenic syndrome (LEMS) twice tested positive for a rare but high-risk blood marker of cancer, called type 2 antineuronal nuclear antibody (ANNA-2), while no tumor was evident, according to a case report.
While LEMS often occurs in the context of cancer, repeat screenings over two years failed to identify cancer in the woman. Researchers noted that this may be the first ever report of a LEMS patient who tested positive for ANNA-2, but does not have cancer.
The case report, “Type 2 Antineuronal Nuclear Antibody in Nontumor Lambert–Eaton Myasthenic Syndrome: A Rare Association With Clinical Implications,” was published as a letter to the editor in the Journal of Clinical Neuromuscular Disease by a group of researchers from Greece.
The 68-year-old woman arrived at the hospital with complaints of dry mouth and muscle weakness, particularly in her lower limbs, lasting for the past six months.
A neurological examination confirmed muscle weakness in her lower limbs and showed she had no reflexes in the muscles of her arms and legs. Blood tests revealed the presence of autoantibodies, or self-targeting antibodies, against voltage-gated calcium channels, the most common cause of LEMS. This led physicians to diagnose the woman with LEMS.
She also tested positive for ANNA-2. Also known as anti-Ri, ANNA-2 are a different type of autoantibodies that are almost exclusively found in people with cancer. These antibodies are particularly associated with lung, breast, and gynecological tumors.
Repeated testing, done nine months later, was again positive for ANNA-2.
“The persistent ANNA-2 seropositivity [positivity based on a blood test] prompted intensive investigation for underlying malignancy [cancer],” the researchers wrote.
The patient’s care team conducted a series of tests looking for an underlying tumor, including computed tomography (CT) and mammography scans every six months for two years. None of the tests have found any sign of cancer.
Researchers noted that two years of screening for a potential cancer is generally considered sufficient in patients who develop LEMS in the absence of any known tumor. However, in this case, “in the light of ANNA-2 seropositivity, it may be prudent to continue screening up to 4 years,” they wrote.
The team also noted that, as far as they are aware, there has never before been a report of a LEMS patient who tested positive for ANNA-2, but did not have cancer.