Combination of Sjögren's syndrome and anti-Ku syndrome complicated by the development of mucosa-associated lymphoid tissue lymphoma: case review and systematic review of the literature.

The frequency of antibodies to Ku varies in various autoimmune diseases. In 2019, Spielmann et al. identified two types of anti-Ku syndrome based on a hierarchical clustering analysis. Sjögren's syndrome occurs both in the first type of anti-Ku syndrome and in the second type. Despite the fact that increased tissue expression of Ku proteins was noted in lymphocytic cells with focal sialoadenitis of the minor salivary glands in patients with primary Sjogren's syndrome, only 49 cases of a combination of anti-Ku antibodies and manifestations of Sjogren's syndrome have been described in the literature. Some researchers examined patients for the presence of Sjogren's syndrome only if they had anti-Ro or anti-La antibodies, although in the literature, there are descriptions of Sjogren's syndrome in the presence of only isolated anti-Ku antibodies, as in our case. Literature data on glandular and extraglandular manifestations of Sjögren's syndrome in anti-Ku-positive patients are limited. Below, we present the first case of Sjögren's syndrome in combination with the first type of anti-Ku syndrome complicated by the development of mucosa-associated lymphoid tissue (MALT) lymphoma. The article also provides a systematic review of the literature on the association of Sjögren's syndrome with anti-Ku antibodies.