RESUMEN
BACKGROUND: Characteristics of primary APS (PAPS) in the youth population have never been studied. In contrast with children, pregnancy is genuinely relevant in the youth age, and understanding clinical characteristics of PAPS patients within this specific age stratum may also provide insights regarding the well-known risk of poor obstetric outcomes during the adolescence. OBJECTIVE: To evaluate clinical and laboratory characteristics of patients with youth-onset PAPS (15-24 years) and compare them with adult-onset PAPS (over 24 years old). METHODS: This was a cross-sectional study derived from two rheumatology outpatient clinics. Patients who fulfilled Sidney criteria and who were 15 years of age or older at disease onset were included. Secondary APS patients were excluded. We subdivided patients into two groups: youth- (15-24 years) and adult-onset (over 24 years) and compared them regarding demographic characteristics, criteria and non-criteria manifestations, cardiovascular risk factors, and aPL status. For the pregnancy outcomes analysis, ever-pregnant patients were divided in three groups: youth-onset, early adult-onset (25-34 years), and late adult-onset (35-49 years). RESULTS: A total of 250 consecutive PAPS patients were included. Groups had a comparable female and Caucasian distribution. We found a similar disease duration (14.0±7.9 vs 17.0±10.1 years, p = 0.079) and similar rates of thrombotic arterial (34.2% vs. 42.0%, p = 0.250) and venous events (69.7% vs. 69.5%, p = 0.975) between them. Skin ulcers were more frequent in the youth-onset group (17.1% vs. 4.0%, p = 0.001), whereas nephropathy was less common (1.3% vs. 8.0%, p = 0.039). No differences were observed for the other criteria and non-criteria manifestations. The adult-onset group presented more frequently with hypertension (p = 0.002), hyperlipidemia (p = 0.008), and smoking (p = 0.003). The youth-onset group presented a higher frequency of obstetric events as the first manifestation of PAPS (30.3% vs. 21.7%, p = 0.005), with worse pregnancy outcomes, namely, fetal death (58.5% vs. 46.4% vs. 24.1%, p = 0.012) and premature delivery (35.8% vs. 19.0% vs. 10.3%, p = 0.016). Of note, all groups had a comparable number of pregnancies (2.81±2.52 vs 2.74±2.07, p = 0.899). CONCLUSION: This study provides novel evidence that youth-onset PAPS presents a higher frequency of obstetric complications as its first manifestation, with an increased risk of fetal death and preterm delivery. Early recognition of this condition by obstetricians is essential to improve prognosis.