High titer of serum antiphospholipid antibody levels in adult Henoch‐Schönlein purpura and cutaneous leukocytoclastic angiitis

Abstract Objective To investigate a possible role of antiphospholipid (aPL) antibodies in adult Henoch‐Schönlein purpura (HSP) and cutaneous leukocytoclastic angiitis (CLA). Methods We reviewed the records of 30 HSP and 8 CLA adults with an initial cutaneous manifestation of palpable purpura on their lower extremities between 2003 and 2007. Eight microscopic polyangiitis (MPA) patients and 30 healthy persons were recruited as controls. Serum anticardiolipin (aCL), anti–phosphatidylserine‐prothrombin complex (anti‐PS/PT), and anti–β 2 ‐glycoprotein I (anti‐β 2 GPI) antibody levels in HSP, CLA, MPA patients, and healthy controls were measured by enzyme‐linked immunosorbent assay. Results Twenty‐two HSP patients (73%) were positive for serum IgA aCL antibodies. Nineteen (63%) had IgA anti‐PS/PT antibodies and 4 (13%) had IgA anti‐β 2 GPI antibodies. IgA aCL and anti‐PS/PT antibodies showed a significant correlation ( P = 0.007). Twenty (67%) HSP patients had IgM anti‐PS/PT antibodies and 6 (20%) had IgG anti‐PS/PT antibodies. Six (75%) CLA patients had IgM anti‐PS/PT antibodies and 2 (25%) had IgG anti‐PS/PT antibodies. In contrast, aPL antibodies were not found in any MPA patients or normal controls. Serum IgA aCL antibody levels in HSP patients showed a significant correlation with serum IgA and C‐reactive protein (CRP) levels ( P = 0.030 and 0.039, respectively). A positive correlation between CRP and serum IgA anti‐PS/PT antibody levels was observed in HSP patients ( P = 0.023). Serum IgA aCL antibody levels were also significantly associated with proteinuria according to urinalysis ( P = 0.024). Conclusion Serum levels of IgA aCL and anti‐PS/PT antibodies were elevated in adult HSP, suggesting that serum IgA antibodies may play some role in adult HSP. IgA aCL and/or anti‐PS/PT antibodies could serve as markers for adult HSP and should be monitored as an indicator of adult HSP activity. Small‐vessel vasculitis could be dependently associated with the presence of IgM anti‐PS/PT antibodies. These findings suggest that aPL antibodies are closely related to the pathogenic factors that trigger the development of vasculitis.