1. ¹School of Child and Adolescent Health, Red Cross Children's Hospital, University of Cape Town, Cape Town, Western Cape, South Africa
2. ²Institute of Infectious Diseases and Molecular Medicine and Division of Medical Microbiology, University of Cape Town, Cape Town, Western Cape, South Africa
3. ³Department of Paediatrics, Faculty of Medicine and the Wellcome Trust Center for Clinical Tropical Medicine, Imperial College of Science, Technology and Medicine, London, UK

Correspondence: Dr Mark P. Nicol, S2.16 Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, 7925 Cape Town, Western Cape, South Africa. E-mail: Mark.Nicol@uct.ac.za

Received 13 November 2006; Revised 3 January 2007; Accepted 30 January 2007; Published online 26 April 2007.

Abstract

Erythema nodosum (EN) may follow a variety of infections, but in regions with a high prevalence of tuberculosis, is frequently associated with a positive tuberculin skin test (TST) and tuberculosis infection. We aimed to investigate the immunological differences between patients with EN as a manifestation of primary tuberculosis, and those with progressive pulmonary tuberculosis (PTB) or asymptomatic infection. We studied the inflammatory response to both mycobacterial and non-mycobacterial antigens in 11 children with EN associated with a positive TST, 22 children with culture-confirmed tuberculosis, and 53 healthy skin test-positive children. In addition, we evaluated functional anti-mycobacterial immunity using an ex vivo assay of mycobacterial growth restriction in five children with EN and 15 with PTB. Patients with EN were distinguished by enhanced mycobacterial growth restriction on the functional assay, which was associated with a markedly increased production of IFN in response to stimulation with purified protein derivative of Mycobacterium tuberculosis. Children presenting with EN and a positive TST show evidence of responses associated with enhanced anti-mycobacterial immunity.