Importance of asking a social history: atypical pulmonary infections and occupational hazards

Abstract

Non-tuberculous mycobacteria (NTM) are ubiquitous in the environment, but NTM infection is limited to individuals with risk factors. We present a case of a 62-year-old man who presented with a 1 year history of cough and shortness of breath. History was notable for significant tobacco use and work as a sandblaster without the use of personal protective equipment. His chest X-ray showed bilateral upper lobe cavitary lesions, which were redemonstrated on chest CT. A sputum Gram stain was positive for acid-fast bacilli, but his tuberculosis QuantiFERON was negative. He was started on empiric tuberculosis treatment. Sputum cultures ultimately returned for Mycobacterium avium intracellulare complex, and treatment was narrowed to azithromycin, rifampin and ethambutol. The case highlights risk factors for NTM infection, notably for this patient, occupational exposures that likely lead to the development of pneumoconiosis. Healthcare providers should ask about occupational history and counsel patients about protection from occupational hazards.

Background

Non-tuberculous mycobacteria (NTM) pulmonary infections have a significant impact on morbidity and mortality. Over 160 different species of NTM exist.¹ Historically, these bacteria have been classified based on the pigment they develop and their rate of growth.² Though these pathogens can cause a variety of infections, pulmonary infections tend to be the most common.³ The mode of transmission of NTM is unclear; however, due to the ubiquity of NTM in soil and water, it is theorised that the mode of transmission is aerosolisation.^{1 3} Direct human-to-human transmission is also possible but infrequent.⁴ NTM infection often does not result in pathological infection in an immunocompetent host.¹ Infection is more common in individuals who are immunocompromised or have underlying lung pathology such as chronic obstructive pulmonary disease, cystic fibrosis and most notably in this case, pneumoconiosis.^{1 3 5} Genetic factors such as impaired mucociliary clearance may also impact the risk of infection.⁶

Recent literature suggests that rates of NTM infections are rising, with Mycobacterium avium and Mycobacterium intracellulare as the most common strains in North America.^{1 7} As NTM infections are not a reportable disease in most countries, estimating the exact number of annual cases is difficult.⁵ Potential aetiologies for the increase in the prevalence of NTM include an increasingly ageing population, a greater prevalence of chronic lung pathology and the widespread availability of diagnostic testing.⁴ We present a case that highlights the role of pre-existing lung pathology in infection from NTM.

Case presentation

A 62-year-old man presented to a primary care office to establish care after experiencing increasing shortness of breath and productive cough for 1 year. An outpatient chest X-ray was performed, demonstrating bilateral upper lobe cavitary lesions (figure 1). Given this finding, the patient was instructed to go to the emergency department for further workup. On further questioning in the hospital, the patient reported that he also had night sweats and fevers over the past several months. He denied unexplained weight loss but did report a decreased appetite. He had not seen a healthcare provider for many years and only reported a medical history of a hydrocoele and hyperlipidemia. On presentation, he did not report taking any medications. Social history was significant for a 45-pack-year smoking history, but he denied alcohol or recreational drug use. The patient remodelled homes and admitted to exposure to a lithium fire, drywalling, mould and animal droppings. In the past, he had also worked as a sandblaster. He wore no personal protective equipment (PPE) during these instances. He also reported having a horse and a rabbit at home. The patient denied a history of incarceration, homelessness, recent travel or intravenous drug use.

Figure 1.

Initial chest X-ray on presentation notable for extensive bilateral upper lobe predominant cavitary process with fibrotic changes.

On physical exam, the patient was thin, non-toxic appearing and resting comfortably on room air. His pulse, respiratory rate, temperature and oxygen saturation were all within normal limits. Respiratory exam revealed decreased air movement, and coarse breath sounds bilaterally. His cardiac exam was unremarkable. On admission, initial differential diagnoses included tuberculosis (TB), malignancy, pneumoconiosis, fungal infection and pneumonia.

Investigations

Given concern for TB, the patient was immediately placed in airborne isolation. A chest CT was obtained, showing large bilateral upper lobe cavitary lesions and diffuse centrilobular nodular opacities (figures 2–3). Initial testing included procalcitonin, HIV, TB QuantiFERON, sputum Gram stain and blood culture. Sputum cultures for bacteria, fungi, and acid-fast bacilli (AFB) were also obtained. Preliminary labs showed negative HIV and procalcitonin. Acid-fast Gram stain was positive for AFB. The infectious disease team was consulted and recommended starting rifampin, isoniazid, pyrazinamide, ethambutol and azithromycin empirically to cover for TB and M. avium complex. Induced sputum was collected every 8 hours for three occurrences, and all specimens showed AFB without specific speciation. TB QuantiFERON was negative. Additional testing included negative histoplasmosis urinary antigen, blastomycosis serum antigen, cryptococcus serum antigen, fungitell assay, legionella urinary antigen and streptococcal urinary antigen.

Figure 2.

CT chest axial plane on initial presentation demonstrates large upper lobe predominant thick walled cavitary lesions and nodular opacities.

Figure 3.

CT chest coronal plane on initial presentation demonstrates large upper lobe predominant thick walled cavitary lesions and nodular opacities.

Treatment

Given these findings, it was suspected that the patient had NTM. He was initially started on rifampin, isoniazid, pyrazinamide, ethambutol and azithromycin. On this regimen, his shortness of breath, cough and sputum production improved. Given culture findings, negative TB QuantiFERON, and his clinical improvement, the antibiotic regimen was narrowed to azithromycin, rifampin, ethambutol and isoniazid.

Outcome and follow-up

After discharge, his AFB cultures speciated to grow M. avium intracellulare complex. He was seen by the infectious disease team, who narrowed his antibiotic regimen to azithromycin, rifampin and ethambutol. Given his large cavitary lesions, a pulmonary referral was made to rule out underlying malignancy. He underwent a diagnostic bronchoscopy with bronchoalveolar lavage (BAL) that demonstrated no endobronchial masses but did show erythematous and friable mucosa. BAL cytology results did not demonstrate malignant cells, and Gram stain did not reveal AFB.

Unfortunately, despite broad antibiotic treatment with ethambutol, azithromycin and rifabutin, he continued to have progression of cavitary lung disease. A repeat CT chest 7 months after initial presentation showed evolving fibrocavitary changes in the upper lungs and peribronchial centrilobular nodular opacities. Given the progression of his disease, inhaled amikacin was initiated, but he could not tolerate this due to dyspnoea and bronchospasms. Sputum cultures 1 year after initial diagnosis continued to remain positive for M. avium intracellulare complex. He reported worsening fatigue, shortness of breath and had a gradual functional decline. Given the progression of his disease, the patient’s sputum sample was sent to National Jewish Hospital to perform special susceptibility testing. After consultation with National Jewish Hospital, the patient was started on intravenous amikacin three times weekly and oral clofazimine daily. He is currently on ethambutol, azithromycin, intravenous amikacin, clofazimine and rifabutin therapy. He continues to follow with his primary care doctor, infectious diseases, pulmonary medicine, and was recently referred to palliative medicine given his progressive functional decline.

Discussion

This case demonstrates the significant impact that prior environmental exposures can have on colonisation with NTM. Previous literature suggests that occupations such as construction work or sandblasting result in occupational exposure to silica, quartz or dust.^{8 9} Exposure to these compounds has been associated with the development of pneumoconiosis. Prior case reports have demonstrated that exposure to such compounds is associated with a variety of pulmonary pathologies, and specifically in NTM.¹⁰ Other recent cases have documented NTM infections in patients with underlying pulmonary pathology.^11–13 Despite these associations, additional research is needed to study if exposure to specific industrial chemicals may lead to a higher predilection for chronic pulmonary pathology. Our patient was a sandblaster and thus may have been exposed to silica. His CT imaging did demonstrate peribronchial nodular opacities, thus it is possible he had underlying pneumoconiosis that served as a nidus for NTM infection. This case highlights the importance of obtaining a thorough social and occupational history to create an appropriate differential diagnosis.

The presentation of large bilateral cavitary lesions also warrants an evaluation of malignancy. The differential diagnosis of cavitary lung lesions is broad and can include abscess, TB, NTM, aspergillosis, vasculitis, emboli, malignancy, sarcoidosis and more.¹⁴ Our team initially anchored on the diagnosis of NTM and did not consider malignancy as a possible aetiology of large cavitary lesions. Studies suggest that indolent pulmonary infections may present with underlying malignancy.¹¹ Furthermore, the non-specific clinical features of NTM and malignancy often overlap. In patients presenting with large cavitary lesions, evaluation for malignancy should be considered.

This case stresses the responsibility of primary care physicians to screen for the use of PPE in individuals with potential occupational exposures. Primary care physicians should consider screening for occupational hazards and counsel patients on using PPE during annual physicals, especially in patients who are immunosuppressed or have underlying pulmonary disease. Proper use of PPE in individuals with occupational hazards can reduce the risk of chronic pulmonary pathology and potentially NTM infections. In summary, physicians should consider asking about occupational hazards during clinical encounters to broaden differentials and provide appropriate counselling.

Learning points.

• The differential diagnosis for cavitary pulmonary lesions is broad and includes but is not limited to an abscess, tuberculosis (TB), non-tuberculous mycobacteria (NTM), aspergillosis, vasculitis, emboli, malignancy and sarcoidosis.

• The risk of NTM infections is greater in those who are immunosuppressed or have underlying pulmonary pathology.

• Occupation history is an important component of a history and physical that may provide critical information about a patient’s condition.

• Primary care physicians should consider screening for occupational hazards and counselling on the use of occupational personal protective equipment during an annual physical exam.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).