Correct!
1. Drug-induced
The most common causes of secondary EP are toxins and drugs. Nearly every class of medication has been implicated in EP but it is more often seen in those taking antibiotics (3). There have been 196 case reports of drug induced eosinophilic pneumonia documented between the years 1990 and 2017. Of the 196 cases, 26 patients required mechanical ventilation. Less common etiologies of EP include fungal and parasitic infections. The term Loffler’s syndrome is generally used when referring to an EP secondary to parasitic infection (1). Helminth larvae, most commonly the Ascaris species, can migrate from the small intestines into the lungs where they mature causing destruction to the capillary and alveolar walls. This process of larvae migration is typically asymptomatic, but can present with cough, low grade fever, dyspnea, and asthma with wheezing (4).
In our case, the patient’s medical history, drug allergies, and IgE specific antigen testing makes determining the etiology of his EP more difficult. His worsening symptoms after antibiotic exposure combined with the skin biopsy results were most consistent with drug induced acute eosinophilic pneumonia. However, this does not rule out an underlying chronic condition. After an extensive chart review, it was found that the patient’s history of chronic sinusitis, cough, and dyspnea on exertion were documented 1 year prior to his admission for EP. At that time, his pulmonologist stated the patient had a normal physical exam, normal imaging, and PFTs. He was unclear of the cause of patient’s persistent dyspnea on exertion that was unrelated to environmental triggers. Additionally, the patient had very low levels of Ascaris specific IgE. The clinical relevance of allergens in that quantity are undetermined and it is unlikely that a helminth infection was the underlying cause of the patient’s acute episode of EP. However, IgE sensitization to Ascaris has been documented to be a clinical indicator of asthma severity (5). It is unclear whether allergic sensitization to Ascaris played a role in this patient underlying illness.
Eosinophilic granulomatosis with polyangiitis (EGPA), previously called Churg-Strauss syndrome cannot be ruled out in our patient. Per the American College of Radiology, a diagnosis of EGPA can be made with a sensitivity of 85% and specificity of 99.7% if four out of six criteria are met: history of asthma, paranasal abnormalities, peripheral eosinophilia of greater than 10%, pulmonary infiltrates, neuropathy, and extravascular eosinophilia on biopsy (6). Our patient’s history of asthma, chronic sinusitis with nasal polyps, peripheral eosinophilia >50% and pulmonary infiltrates meet these criteria. Given this information, serum anti-neutrophil cytoplasmic antibody (ANCA) was ordered at a follow up visit three months after the patients discharge as ANCA is positive in 40% of EGPA cases. This was negative, placing a diagnosis of EGPA lower on the differential but not entirely ruled out.
References