A Systematic Review on the Epidemiological Data of Erythema Nodosum Leprosum, a Type 2 Leprosy Reaction

Abstract

BackgroundErythema Nodosum Leprosum (ENL) is a humoral immunological response in leprosy that leads to inflammatory skin nodules which may result in nerve and organ damage, and may occur years after antibiotic treatment. Multiple episodes are frequent and suppression requires high doses of immunosuppressive drugs. Global occurrence is unknown.Methodology/Principal FindingsSystematic review of evidence on ENL incidence resulted in 65 papers, predominantly from India (24) and Brazil (9), and inclusive of four reviews. Average incidences are based on cumulative incidence and size of study populations (n>100). In field-based studies 653/54,737 (1.2%) of all leprosy cases, 194/4,279 (4.5%) of MB cases, and 86/560 (15.4%) of LL cases develop ENL. Some studies found a range of 1–8 per 100 person-years-at-risk (PYAR) amongst MB cases. Hospital samples indicate that 2,393/17,513 (13.7%) of MB cases develop ENL. Regional differences could not be confirmed. Multiple ENL episodes occurred in 39 to 77% of ENL patients, with an average of 2.6. Some studies find a peak in ENL incidence in the first year of treatment, others during the second and third year after starting MDT. The main risk factor for ENL is a high bacteriological index.Conclusions/SignificanceFew studies reported on ENL as a primary outcome, and definitions of ENL differed between studies. Although, in this review averages are presented, accurate data on global and regional ENL incidence is lacking. Large prospective studies or accurate surveillance data would be required to clarify this. Health staff needs to be aware of late reactions, as new ENL may develop as late as five years after MDT completion, and reoccurrences up to 8 years afterwards.

Coinfection of leprosy and tuberculosis

“…The prevalence rates of ENL are highly variable with average incidences in field-based populations for all leprosy cases (1.2%) and for MB leprosy cases (4.5%) and 37% in a hospital samples of patients with MB leprosy 15. Literature shows that ENL may occur before, during or after MDT and even several years later.…”

“…Literature shows that ENL may occur before, during or after MDT and even several years later. However, one systematic review of ENL cases noted that the incidence of ENL is at least twice as high during MDT than at the time of the initial diagnosis, with the highest incidence in the first year of MDT 15. One study16 has noted leprosy reactions with concurrent TB infection; however, precipitating factors could not be elicited.…”

The Mortality Associated with Erythema Nodosum Leprosum in Ethiopia: A Retrospective Hospital-Based Study

“…It is acknowledged that there is a lack of good epidemiological data on the true incidence of ENL [5].…”

Complex Type 2 Reactions in Three Patients with Hansen's Disease from a Southern United States Clinic

“…Finally, as illustrated in this case series, recurrences of T2R are common and therefore necessitates close follow-up of patients. 33 …”