In this report, we encountered an unusual case who suffered from HSP on day 8 after scabies. As there is no definitive test for HSP diagnosis, the 2008 European League Against Rheumatism criteria are still the most commonly used guideline for HSP diagnosis [4]. On this basis, our patient fulfilled 3 criteria (nonthrombocytopenic purpura, abdominal pain and renal involvement), and thus the diagnosis of HSP was made undoubtedly after scabies. To the best of our knowledge, very few previous studies have documented that cutaneous vasculitis can be secondary to or coexisting with scabies [5]. Furthermore, Liu et al. [6] tracked 4481 scabies patients for a 7-year period and found that scabies lead to a 5.44-fold increased risk for hypersensitivity vasculitis, a 4.91-fold increased risk for dermatomyositis, a 2.89-fold increased risk for polyarteritis nodosa, a 2.73-fold increased risk for systemic lupus erythematosus respectively, compared with the healthy population. According to the current limited evidence, we speculated that the potential mechanisms of scabies-associated HSP may be attributed to the host response to antigens on Sarcoptes scabiei var. Hominis, such as immune-complex mediated injury, cytotoxic T-cell-mediated immune responses and autoimmune reactions. Further studies are warranted to clarify their shared etiologies and relationships.
As for the present case, another unique feature was the positive ANA, whereas the other diagnostic criteria for systemic lupus erythematosus (SLE) were absent. In fact, HSP and SLE share several commonalities such as their own characteristic rashes and a multi-system involvement. In our previous report, we encountered an unusual female patient who suffered from HSP at 3 months after diagnosis of SLE. Distinct from the present case, her autoimmune serologic workup indicated positive anti-dsDNA/anti-SM and low C3/C4 besides positive ANA [7]. ILE patients had at least one but less than four of the American College of Rheumatology(ACR) classification criteria of SLE and did not present distinctive clinical features or meet classification criteria of other connective tissue diseases [8]. Although the majority of ILE patients may never reach SLE classification, about 10%-50% of ILE patients are at high risk of progressing to complete SLE within 5 years [9]. In southern Sweden, Hallengren et al. [10] followed up 28 ILE patients for a 10-year period and found that 16 of 28 patients developed complete SLE, and malar rash and anti-cardiolipin antibodies were the potent predictors of complete SLE; in addition, positive Wasserman and ANA, thrombocytopenia, arthritis and early involvement of multiple organs could also serve as the candidates of risk factors for development of complete SLE. Based on the experiences from adult ILE, antimalarial drugs may play a beneficial role in limiting organ damages, delaying complete SLE onset, slowing the accrual of autoantibodies and reducing the need for drugs with greater toxicity, but which has not yet been formally tested in longitudinal studies and even in pediatric patients [11].
During the period of hospitalization, our patient suffered from acute kidney injury and had persistent proteinuria. The histopathological examination of the renal biopsy specimen showed that the pathological classification was class IIIb. As we all know, the degree of proteinuria has been proven to be not only a sign but an accelerator of nephropathies. A recent single-center study from Shanghai Children’s Hospital showed that the pathological classification in 62.97% of HSP patients with nephrotic proteinuria were above the ISKDC class III [12]. Currently, the main treatments of HSP nephritis encompass corticosteroids alone or plus immunosuppressors. Feng et al. [12] administered methylprednisolone and mycophenolate mofetil to 54 HSP patients with nephrotic proteinuria, and found that 68.52% of patients had complete remission and no patient progressed to end-stage renal disease after a follow-up of 6 months to 5 years. In the present report, it should be noted that corticosteroids and immunosuppressors may increase the relapse risk of scabies, therefore this patient should be followed up carefully after discharging from our department.