arthritis of the spine, resembling rheumatoid arthritis, that may progress to bony ankylosis with lipping of vertebral margins; the disease is more common in the male often with the rheumatoid factor absent and the HLA antigen present. There is a striking association with the B27 tissue type and the strong familial aggregation suggest an important genetic factor, perhaps inherited as an autosomal dominant [MIM*106300]; the mechanism, however, remains obscure. Syn: Marie-Strümpell disease, rheumatoid spondylitis, Strümpell-Marie disease.