Historically, archaeological evidence, post-mortem findings and retro-
spective analysis of leprosy institutions’ data demonstrates a high observed incidence
of concomitant infection with leprosy and tuberculosis (TB). However, reports of
concomitant infection in the modern literature remain scarce, with estimates of
annual new case detection rates of concomitant infection at approximately 0·02
cases per 100,000 population. Whilst the mechanism for this apparent decline in
concomitant infections remains unclear, further research on this topic has remained
relatively neglected. Modelling of the interaction of the two organisms has suggested
that the apparent decline in observations of concomitant infection may be due to the
protective effects of cross immunity, whilst more recently others have questioned
whether it is a more harmful relationship, predisposing towards increased host
mortality. We review recent evidence, comparing it to previously held understanding
on the epidemiological relationship and our own experience of concomitant infection.
From this discussion, we highlight several under-investigated areas, which may
lead to improvements in the future delivery of leprosy management and services, as
well as enhance understanding in other fields of infection management. These
include, a) highlighting the need for greater understanding of host immunogenetics
involved in concomitant infection, b) whether prolonged courses of high dose steroids
pre-dispose to TB infection? and, c) whether there is a risk of rifampicin resistance
developing in leprosy patients treated in the face of undiagnosed TB and other
infections? Longitudinal work is still required to characterise these temporal
relationships further and add to the current paucity of literature on this subject matter.