Spontaneous healing of Mycobacterium ulcerans disease in Australian patients

Abstract

Background

Mycobacterium ulcerans causes necrotising infections of skin and soft tissue mediated by the polyketide exotoxin mycolactone that causes cell apoptosis and immune suppression. It has been postulated that infection can be eradicated before the development of clinical lesions but spontaneous resolution of clinical lesions has been rarely described.

Methodology/Principal findings

We report a case series of five Australian patients who achieved healing of small M. ulcerans lesions without antibiotics or surgery. The median age of patients was 47 years (IQR 30–68 years) and all patients had small ulcerative lesions (median size 144mm ², IQR 121-324mm ²). The median duration of symptoms prior to diagnosis was 90 days (IQR 90–100 days) and the median time to heal from diagnosis without treatment was 68 days (IQR 63–105 days). No patients recurred after a median follow-up of 16.6 months (IQR 16.6–17.9 months) from the development of symptoms and no patients suffered long-term disability from the disease.

Conclusions

We have shown that healing without specific treatment can occur for small ulcerated M. ulcerans lesions suggesting that in selected cases a robust immune response alone can cure lesions. Further research is required to determine what lesion and host factors are associated with spontaneous healing, and whether observation alone is an effective and safe form of management for selected small M. ulcerans lesions.

Author summary

Mycobacterium ulcerans causes a destructive infection of skin and soft tissue known as Buruli ulcer that when severe can lead to serious long-term deformity and disability. It is currently not well documented whether people with Mycobacterium ulcerans disease can cure themselves without treatment. In our study we describe five people with small ulcers who cured their disease without specific medical or surgical treatment. This suggests that a proportion of people can develop an immune response sufficient enough to eradicate the disease without the help of medical intervention. This is an important step, as recognition of this possibility provides important further insights into the human immune response against the disease. It also opens the possibility to further studies that may determine characteristics of the organism and hosts that favour spontaneous healing of lesions. This knowledge may in turn improve efforts to prevent and control the disease which are currently lacking.