Buruli ulcer is an infectious disease found in tropical regions of Africa, America, Asia, and Australia with West Africa as the main endemic area. It is caused by the bacterium Mycobacterium ulcerans and presents as severe skin lesions which can progress to bone damage. It can affect all age groups although is predominantly seen in children.
Previous research has classified different presentations of the disease from skin nodules to plaques and ulcers. Lesions can present at either one site of infection or at multiple places on the body (multifocal). They vary in size, with lesions with a diameter larger than 15 cm usually classified as more severe. The World Health Organization (WHO) recognizes three levels of severity; 1) lesion diameter 15 cm associated with multifocal lesions, bone damage and /or at a critical site on the body.
An extensive category III oedematous lesion involving the anterior and posterior chest and neck regions, with two ulcers: one at the anterior triangle of the neck, measuring 6 cm x 8 cm, and another over the midsternal region of the chest, measuring 3 cm x 4 cm.
In this study, researchers from the Life and Health Sciences Research Institute in Portugal and from the Buruli Ulcer Treatment Center of Allada in Bénin examined records of 476 patients in Benin, West Africa, who had Buruli ulcer confirmed through laboratorial investigation. The average (median) age at disease diagnosis was 12 years, with 67% of patients 15 years or under. In order to explore how the disease progresses they studied the statistical relationship between lesion presentation and the time between the first signs or symptoms of the disease remembered by the patient and attendance for medical care.
Of the 476 patients studied 32% presented with a non-ulcerated form of skin lesion (nodule, edema or plaque) while 67% presented with ulcerated lesions and 1% with bone damage. In the non-ulcerated forms the average (mean) time delay between symptoms and medical care was 32.5 days while for ulcerated forms it was 60 days. This difference was shown to be statistically significant which supports previous research, strongly suggesting disease progression from non-ulcerated to ulcerated skin lesions.
A further analysis was carried out on the relationship between lesion severity and the time delay between symptoms and medical care. 33% of patients had lesions at the most severe WHO defined category with 66% at categories 1 and 2. Interestingly in this case no statistical difference was seen between the mean time delay for severe category 3 lesions (60 days) and category 1 and 2 lesions (60 days). Disease progression in the other two types of severe lesions (multifocal lesions and large lesions) was also not affected with time delay to seek medical care. This suggests that rather than lesions becoming progressively more severe the larger lesions represent a separate phenotype of disease.
This study strengthens previous observations of disease progression in a laboratorial confirmed group of patients with Buruli ulcer, and also proposes that more severe presentations of the illness should be considered as a different form of the disease. This highlights the importance of early diagnosis and treatment to avoid ulceration of lesions, as well as paving the way for further pathological studies to identify the mechanisms behind the separate severe phenotypes.
The study is published in PLOS Neglected Tropical Diseases.