Current Allergy & Clinical Immunology

For the past couple of weeks, Dr Goodheart has been seeing a 15-month-old boy, Nathan, who had a history of recurrent infections requiring longer than usual courses of intravenous antibiotics and also two intensive care unit admissions. Based on previous laboratory results, Nathan had low to absent IgG and IgA but normal to raised IgM antibody levels. B and T lymphocyte counts were normal. Dr Goodheart’s suspicion of a possible X-Linked Hyper IgM Syndrome (due to defects in CD40Ligand-CD40 interaction)1,2 as underlying immune defect increased when she found out that two of Nathan’s uncles had died in early infancy due to severe infections.

Part three of this four-part series continues to evaluate the relationship between the human species and the human gut microbiome. It focuses on whether their relationship is symbiotic, parasitic or somewhere in between. The possibilities, based on animal studies, are explored and compared to scientific facts proven in human beings. In particular, close attention is paid to the relationship between the gut microbiome and central nervous system, and the effect this has on human behaviour. This relationship is termed the ‘microbiome–gut–brain axis’. Through a number of pathways, the gut microbiome has an influence on stress (both acute and chronic), anxiety, loneliness and depression, as well as on odour and attraction. It has also been associated with the development of neurodegenerative diseases such as Alzheimer’s and Parkinson’s, and with associated cognitive decline. Since the common treatments used for these conditions are not equally effective in all patients, it is vital for clinicians to explore other avenues that could be used as therapeutic targets. The gut microbiome, in particular, requires further research in order to aid the development of future therapies for certain conditions. The concept of the organisms in the microbiome controlling the mind of human beings is relatively new, but such control has been demonstrated through multiple examples in the animal kingdom. Animal studies in this regard have shown promising results, but human studies are infrequent and often present disappointing results. Randomised control trials in human beings are greatly needed, either to prove or to disprove, the effects of the gut microbiome on complex psychiatric diseases.

In cases of workers previously exposed to asbestos and subjected to screening programmes for asbestos-related lung disease, it is possible that clinicians may not consider investigating them further for other possible aetiologies for their lung disease. This case involves a 58-year-old male fitter and turner employed at a naval dockyard. The patient presented with worsening symptoms of dyspnoea and a change in chest X-ray findings during an asbestos-screening programme. After further investigation that included high-resolution computed tomography and a lung biopsy, the histological picture was in keeping with a diagnosis of hard-metal lung disease. This case highlights the necessity of always considering a differential diagnosis in workers with exposure to multiple respiratory toxins and pathogens. This requires a thorough clinical examination to be performed. Such an examination should elicit a comprehensive occupational history that details all exposures and relevant special investigations in order to ensure that one does not fail to make the correct diagnosis.