Correlation Study Between Erythema Nodosum, Nodular Vasculitis And Mycobacterium Tuberculosis Infection

BackgroundErythema nodosum and nodular vasculitis are two common forms of panniculitis presumably caused by infection, drugs, estrogen and other systemic diseases. It is assumed that tuberculosis infection is the most prominent cause of the two panniculitis in countries with high Mycobacterium tuberculosis prevelence such as China. However, this hypothesis lacks of solid laboratory evidence. The most used TB diagnostic method in China, tuberculin skin test (TST), is not an ideal test, as it has cross-reactive response to BCG vaccine and other none TB mycobacteria, resulting in high false positive rate and subsequently low specificity. False positivity result in over-treatment with anti-tuberculosis drugs and body injury, and false negativity may delay the diseases.ObjectiveThis study aims at more efficient and sensitive methods for detecting TB infection rate in patients with erythema nodosum or nodular vasculitis. The current study investigates the relationship between erythema nodosum, nodular vasculitis and TB infection by comparing the immunological and molecular test results.MethodsQuantiFERON-TB Gold and Real-Time PCR detection of IS6110of Mycobacterium sp. and mpt64gene of Mycobacterium tuberculosis complex were carried out in all groups of subjects, including36patients with erythema nodosum,27patients with nodular vasculitis,44patients with other vasculitis and31control subjects. Both QuatiFERON and Real-Time PCR results from different groups were compared to evaluate whether TB infection is correlation with erythema nodosum, nodular vasculitis, or other vasculitis.ResultsNineteen out of32patients (59%) with erythema nodosum,20out of26patients (77%) with nodular vasculitis and17out of36patients (47%) with other vasculitis had positive QuatiFERON results, which were all significantly higher than the infection rate of the control group (p<0.05).The positive rate of IS6110gene in the erythema nodosum group was31%(7/23), which although not significant, but had trend higher than the control group (p=0.08). The positive rate of IS6110gene in the nodular vasculitis group was37%(7/19), which was higher than that of the control group (p<0.05). The positive rate of IS6110gene in other vasculitis group was only9%(3/34), showing no difference comparing with the control group (p>0.05).ConclusionsOur study found out that the tuberculosis infection rate of the patients with nodular vasculitis, erythema nodosum, and other vasculitis were77%,59%,47%of respectively, which was significantly higher than the control group, suggesting that the incidence of nodular vasculitis, erythema nodosum, and other vasculitis may be caused by an immune response of TB infection.Tuberculous bacteriological evidence was also found in the lesions of37%patients with nodular vasculitis, which was significantly higher than the control group. This indicates that the nodular vasculitis might be correlated with TB infection.The current bacteriological evidence is not sufficient to show whether erythema nodosum is correlated with TB infection. A larger sample needs to be detected to see if there is any relationship between these two in future research.