Not only is active pulmonary tuberculosis (TB) a highly contagious disease, but it is also the current leading cause of death from a single infectious pathogen. According to a 2018 report, approximately 7 million new and relapsed TB cases were reported globally.
While there is extensive research regarding the clinical symptoms of active TB, knowledge on the overall underlying biochemical mechanisms that lead to these symptoms and systemic complications is quite scarce and, if available, relatively outdated.
In 2020, Dr Laneke Luies and Dr Ilse du Preez from the Human Metabolomics department at the North-West University (NWU) published a paper titled: The Echo of Pulmonary Tuberculosis: Mechanisms of Clinical Symptoms and Other Disease-Induced Systemic Complications in Clinical Microbiology Reviews.
Their paper aimed to give detailed and current information on the biochemical mechanisms that lead to clinical symptoms and systemic complications. This summative information could bridge the gap between the knowledge of the patient, clinician and researcher.
According to the paper, the best-known symptoms of active TB can be classified as local, in other words relating to the site of the infection (lungs). These include, for example, mucus (phlegm) over-production, difficulty breathing and coughing of blood.
In addition, various systemic symptoms involving the entire body can also occur, such as fever, night sweats, tiredness and severe weight loss. Despite these visible signs, TB is also associated with less obvious, sometimes “invisible” systemic variations of which patients are most likely unaware. These include an increase in oxidative stress, hyponatremia (abnormally low sodium level in blood), hypocholesterolaemia (low blood cholesterol levels), vitamin D deficiency, glucose intolerance, haematological (blood) abnormalities, altered microbiota (resident bacteria crucial to human health).
It should be emphasised that the clinical symptoms of pulmonary TB are often non-specific, and that gender, age, co-morbidities, ethnicity and other factors can all affect the presentation of the patient. A better understanding of these inter-individual variations and the biochemical cause(s) thereof could lead to earlier diagnosis and more effective treatment.
Although in the past 20 years newer omics research techniques have contributed substantially to the understanding of various aspects of TB disease and host response mechanisms, Dr Luies and Dr Du Preez say that it is evident this field is still in need of extensive, elaborative research.
The new knowledge could pave the way for the development of more effective TB treatment procedures.
