Maternal age and family history are risk factors for ankylosing spondylitis.

Objective: To investigate prevalence and gender distribution in parents of children with ankylosing spondylitis (AS).

Methods: Family history of AS (parents, uncles, and aunts), maternal age at delivery, and consecutive pregnancy number were assessed in the relatives of 40 Mexican Mestizo patients with definite AS (New York Criteria).

Results: We evaluated the family history of AS in 34 families of 40 AS patients; 12 with none, 4 with a paternal history (4 healthy fathers with a brother with AS) (odds ratio, OR, 1.37, p = 0.75), 15 with a maternal history of AS, (15 healthy mothers with a brother with AS) (OR 1.4, p = 0.55), and 3 with both lines (OR 0.84, p = 0.92). In these families AS was more frequent in males (29%) than in females (10%), OR 3.40 (95% confidence interval, CI: 1.43-8.29, p = 0.003). Juvenile onset was more common in the offspring of mothers with family history (72%) (OR 13.0, 95% CI: 1.68-147.48, p = 0.009). The number of first-born children with AS (18%) was similar to the later-born children (23%) (OR 1.37, 95% CI: 0.38-5.31, p = 0.78). The frequency of AS increased when the maternal age at delivery was < or = 30 years (OR 0.20, 95% CI: 0.04-0.75, p = 0.01).

Conclusion: In Mexican Mestizo patients, there is no correlation between the risk for AS and the gender of the affected parent. However we found an association between juvenile onset and maternal family history with an increased incidence in patients with younger mothers.