The influence of pregnancy on the course of ankylosing spondylitis (AS) was evaluated for 87 pregnancies of 50 patients. Remission of AS was recorded in 18 pregnancies, exacerbation in 21, and no change in 48. A short flareup of AS was noticed postpartum in 45% of the patients. Postpartum anterior uveitis occurred frequently (20%). The first symptoms of AS were often (20%) related to pregnancy. AS had no harmful effect on pregnancy, the fetus, or the newborn. Twelve percent of the offspring who were 18 years old or older have developed definite ankylosing spondylitis.

Only 5% of AS patients are B27 negative. We describe two cases of HLA-B27 negative AS in a father and a son who both developed clinical and radiological features characteristic of AS. Tissue typing for HLA-A,-B,-C was performed in all 1.degree family members except for the father who died in 1990. All family members possessed B40. HLA-B40 may contribute to an increased susceptibility for AS not only in B27 positive individuals but also in B27 negative cases.

Demonstration of chlamydial antibodies in patients with ankylosing spondylitis (AS) could show an etiological role of Chlamydia trachomatis in this condition. We studied serum specimens from 50 HLA-B27 positive patients with AS (Group I), 34 HLA-B27 positive patients with other rheumatic diseases (Group II), 67 HLA-B27 positive healthy blood donors (Group III) and 37 healthy untyped blood donors. (Group IV). Measured by an immunoperoxidase assay (IPA) chlamydial IgA (titre greater than or equal to 1:20) was more prevalent in the HLA-B27 positive persons than in the healthy controls not selected for HLA-group (Groups I + II + III vs IV : p less than 0.02). Chlamydia trachomatis IgA-IPA containing sera also had specific IgG-IPA antibodies (greater than or equal to 1:80) in 29 (96%) out of 30 sera from HLA-B27 positive individuals and controls. Conversely, 45% of specific IgG-positive (greater than or equal to 1:80) AS sera, 27.7% sera in Group II, 39.4% Group III sera vs. 11.1% of sera in Group IV had concomitant chlamydial IgA (greater than or equal to 1:20). The differences in the prevalence of specific IgA were statistically significant: Group I vs. IV : p less than 0.01; Group III vs. IV :p less than 0.05 and Gr. I + II + III vs. IV: p less than 0.05. Our data suggest an enhanced antibody production against Chlamydia trachomatis among the HLA-B27 positive individuals whether they have AS or are healthy.

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