Antinuclear antibody (ANA) can be positive in children with primary immune thrombocytopenia (ITP), but the effect of ANA titre and its variation on outcomes of children with primary ITP remains unclear. Here, we conducted a single-centre retrospective cohort study of children with primary ITP at the Peking Union Medical College Hospital in China. A total of 324 children with primary ITP included in this study were followed for a median time of 25 months. In this cohort, 39.2% had an ANA titre of 1:160 or higher. Results from a generalized estimating equation model revealed that patients with higher ANA titres had lower platelet counts at onset but a higher recovery rate of subsequent platelet counts. Results from Cox regression models adjusted for potential confounders revealed that patients with ANA titres of 1:160 or more were more likely to develop to autoimmune disease (AID) than those without, and the risk of AID development increased with the rise of ANA titres (p value for trend less than 0.001). These data highlight the predictive value of ANA titre for platelet counts and the risk of AID development in children with primary ITP.

Background Neonatal‐onset hereditary thrombotic thrombocytopenia purpura (hTTP) is often misdiagnosed due to its rarity. It begins with jaundice, similar to infants with ABO incompatibility. Objective To explore early indicators of neonatal‐onset hTTP. Methods This study was a retrospective case series of newborns with hTTP and ABO incompatibility. We compared the clinical characteristics and laboratory test results in these two groups. Results This study included four hTTP patients and 20 ABO‐incompatible newborns. All patients manifested disease during the neonatal period. There were equal numbers of males and females in each group. hTTP newborns showed earlier (median difference, 57.0 h; 95% confidence interval [CI], 24.0–65.0) and more severe hyperbilirubinemia (mean difference, 8.0 mg/dl; 95% CI, 3.8–12.1) than ABO‐incompatible newborns. In hTTP newborns, anemia was more common within 7 days after birth than in ABO‐incompatible newborns (odds ratio, 25.4; 95% CI, 1.2–551.6), and platelet counts were lower than in ABO‐incompatible newborns (17 ± 12 × 10 9 /L vs. 291 ± 76 × 10 9 /L). The levels of serum creatinine (median difference, 51.8 μmol/L; 95% CI, 16.0–109.4) and blood urea nitrogen (median difference, 5.7 mmol/L; 95% CI, 2.8–38.7) were higher in hTTP newborns than in ABO‐incompatible newborns. There were no significant differences in white blood cell counts, C‐reactive protein, alanine aminotransferase, or albumin levels. Conclusions Severe jaundice soon after birth, early anemia, and severe thrombocytopenia were more common in newborns with hTTP than ABO incompatibility. These are distinguishing early features of hTTP.