Musculoskeletal tuberculosis: are you ready to diagnose it?

Abstract

Tuberculosis (TB) is far from being eradicated from the world (1). Despite the scarcity of this disease in high-income countries, including the Nordic ones, there are 1.7 million deaths (2) and more than 9 million new cases annually in the world (3): this number is higher than at any time in history. In particular, the low-income countries in sub-Saharan Africa bear the greatest burden. For example, in South Africa about 1% of the population develops tuberculosis each year, much of it due to HIV (1). Also, the homeless people around the world are at greater risk of being infected with TB. For example, in 2009 there were 9040 cases of tuberculosis in the UK, that is 15 cases per 100,000 individuals. However, the disease is concentrated in certain demographics within certain areas. London has a rate of 44 cases per 100,000. In the country’s homeless population, the rate is 300 cases per 100,000 (4). In contrast, the Nordic countries have 3–7.7 new cases each year for 100,000 people, but the incidence in Baltic countries and, in particular, in Russia is much greater reaching close to 100 per 100,000 in the latter. But, why we should be worried about TB, since it is uncommon in people born in Nordic countries? The answer is simple. The demographics are changing at a great speed. Thus, we are faced more and more with immigration and patients born in countries with a high prevalence of TB. Moreover, people are traveling more and often to countries with high numbers of TB. For example, recent complete data show that 30% of new cases in Finland were of foreign origin (5). In 1996, Acta Radiologica included a series of five studies on different manifestations of TB (6–10). Since then, 32 papers on or related to TB have been published in this journal, of which half were published after year 2000. Most of the papers are related to pulmonary or CNS tuberculosis. This is understandable, because TB predominantly affects the lungs. However, it can cause disease in any organ, including the musculoskeletal (MSK) system, and must therefore be included within the differential diagnosis of a large range of clinical presentations (3). Also, it should be kept in mind that extrapulmonary tuberculosis in adults remains a great diagnostic challenge. Tuberculosis of the MSK system is rare, and accounts for only up to 3% of all TB infections (11), and medical awareness of these more unusual presentations of TB is often low in developed countries. Despite this, it is mandatory for the MSK radiologist to know the most common presentation and imaging features of MSK TB, since prompt diagnosis allows the start of the proper medication without any unnecessary delay. Also, it is clear that for the younger generation MSK TB is very rarely, if ever, seen in clinical practice. In a recent issue, Professor Andronikou and his colleagues shared their vast experience of imaging features of MSK TB using plain radiographs as well as modern imaging technology, i.e. CT and MRI (12). Since 1996, no paper dedicated to MSK TB has been published in this journal. Therefore, this paper is highly recommended reading for all radiologists that wish to broaden their knowledge beyond TB spondylitis, the most common form of MSK TB. Be prepared for the 21st century.