A first case of an autoimmune disorder characterized by inflammation of blood vessels in a bronchiectasis patient infected with Mycobacterium abscessus highlights the therapeutic challenges in managing nontuberculous mycobacteria (NTM) infections.
The case report, published in BMC Pulmonary Medicine, is titled “Microscopic polyangiitis secondary to Mycobacterium abscessus in a patient with bronchiectasis: a case report.”
Mycobacterium abscessus is greatly associated with lung infection among patients with bronchiectasis, and is an important cause of morbidity among this patient population.
Patients with chronic lung diseases, including bronchiectasis, are at higher risk of contracting NTM infections, which are caused by inhalation of members of the bacteria genus Mycobacterium, such as Mycobacterium abscessus.
Mycobacterium abscessus is difficult to eradicate, and usually requires long-term antibiotic therapy; however, this can promote the development of multi-drug-resistant bacteria strains.
Damage to blood vessels (vasculitis) is a rare complication of NTM lung infections, reported more commonly among patients with an impaired immune system.
In this report, clinicians describe a case of vasculitis as a consequence of Mycobacterium abscessus infection in a 70-year old woman with bronchiectasis diagnosed with NTM pulmonary disease.
The patient had been symptomatic, with a persistent, non-productive cough and recurrent chest infections for 10 years. She did not smoke, and had no history of respiratory disease in childhood.
The woman developed paraesthesia (abnormal sensation of tingling) in her hands and feet, associated with arthralgia (joint pain), as well as sensorimotor neuropathy (a condition characterized by decreased ability to move or feel because of nerve damage).
Blood analysis revealed she was positive for a specific class of autoantibodies against a type of white blood cells — neutrophils — called antineutrophil cytoplasmic antibodies (ANCA). Autoantibodies are generated when there is a failure of the immune system to recognize and distinguish the body’s own cells (“self”) from foreign cells, e.g. bacteria and viruses (“non-self”).
The patient was diagnosed with an autoimmune disease called microscopic polyangiitis, characterized by inflammation and damage of blood vessels (vasculitis) as a result of ANCA antibodies.
Blood analysis also revealed lower levels of a protein important for fighting infections, called interferon-gamma, but no other significant alterations in the immune system.
M. abscessus was isolated from her sputum.
The patient received dual therapy with immunosuppressants (including corticosteroids and cyclophosphamide) to treat the underlying vasculitis, and antimicrobial therapy for M. abscessus infection.
Clinical stability, however, was difficulty to achieve, as reductions in her immunosuppression regimen led to worsening of vasculitis flares. In fact, one flare led to a blockage in a vein in the eye, leading to vision loss.
Clinicians increased her immunosuppression therapy, and moved her to a treatment with rituximab and corticosteroid therapy plus methylprednisolone given intravenously for four weeks, followed by six months of rituximab alone.
However, this strategy resulted in a worsening of her NTM lung disease, forcing clinicians to change her antibiotics.
Up to the end of the study, the patient was still positive for M. abscessus bacteria, and was receiving pulsed intravenous antibiotics at intervals determined by clinical symptoms.
Overall, “this case highlights a rare systemic complication of NTM [pulmonary disease] and is the first reported case of ANCA-positive vasculitis as a consequence of M. abscessus infection,” the researchers stated. “It demonstrates the complexity of managing NTM PD including therapeutic challenges and the relationship between immune function and NTM infection.”
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