P031 Montelukast antagonising underlying systemic illness
Authors: Connerton Áine 
Published: April 2023

Abstract

Background/Aims
Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare, multisystemic, autoimmune vasculitis involving small to medium-sized blood vessels. It has a well-established affiliation with atopic syndromes, typically adult-onset asthma and sinusitis. More rare associations are linked with drug side effects such as Montelukast. According to the ‘American College of Rheumatology 1990’, the following criteria yield a sensitivity of 84% in identifying a patient with EGPA. The criteria include: asthma, eosinophilia &gt;10% on differential white cell count, mononeuropathy or polyneuropathy, transient pulmonary infiltrates on chest radiography, paranasal sinus abnormality, and blood vessel biopsy demonstrating extravascular eosinophilia, in a patient with symptoms of systemic vasculitis. The multisystemic involvement of EGPA makes both diagnosis and management difficult as presentations can vary.

Methods
We report the complex case of a 61 year-old gentleman diagnosed with EGPA. His relevant past medical history includes a diagnosis of Asthma in 2002 (managed with inhaled bronchodilators, corticosteroids, and montelukast), recurrent sinusitis, and lower respiratory tract infections. The patient presented with a one month history of abdominal cramping and bloating. This was associated with nausea, constipation, anorexia, and a week of ‘drenching’ night sweats. His full physical examination during this time was unremarkable.

Results
He had a normal CT Abdomen Pelvis and colonoscopy. His admission chest radiograph demonstrated bilateral parenchymal lung changes. This was followed by a CT Thorax showing bilateral upper and lower lobe bronchiectasis. Mediastinal and hilar adenopathy consistent with a diagnosis of allergic bronchopulmonary aspergillosis with associated reactive adenopathy. His laboratory investigations showed eosinophilia (21.68) and leucocytosis (32.7). In view of these results, an autoantibody screen was sent showing positive ANCA and positive anti-Myeloperoxidase antibodies(MPO titre 55). Two days into his admission he developed pain and paralysis of his right upper limb. He reported marked fatigue followed by a petechial, non-blanching, vasculitic rash on both ankles. Neurological examination reflected a subacute symmetrical sensory and motor polyneuropathy predominantly involving the right side with bilateral foot drop. MRI Brain demonstrated an established infarct in the left external capsule. He was commenced on high dose aspirin. Due to high suspicion for EGPA, methylprednisolone was commenced for 5 days, followed by tapering oral corticosteroid therapy and Rituximab therapy. A skin punch biopsy showed ‘ a vasculopathic type reaction with small vessel vasculitis, associated mixed inflammatory infiltrate which includes some eosinophils’ confirmed his diagnosis.

Conclusion
A topic of particular relevance to this case is the association between EGPA and montelukast. It has been hypothesised that there may be a relationship between Leukotriene Receptor Antagonist Therapy, specifically Montelukast, with the pathogenesis of EGPA. Some research suggests that treatment with Montelukast permits the decreased need for oral corticosteroids for asthma control. Therefore, suggesting that EGPA could have been masked by corticosteroid therapy.
Disclosure
Á. Connerton: None.