Discussion :
Amiodarone is one of the most commonly prescribed medications for the
treatment of life-threatening ventricular arrhythmia.
Treatment with amiodarone has various known neurologic, ophthalmic, bone
marrow
cutaneous, thyroid, hepatic, and pulmonary side effects.
Pulmonary toxicity is among the most serious adverse effects of
amiodarone.
Interstitial pneumonitis, eosinophilic pneumonia, organizing pneumonia,
acute respiratory distress syndrome, diffuse alveolar hemorrhage, lung
mass or consolidation, and rarely pleural effusion can occur in
amiodarone toxicity. [5]
Among these various types of pulmonary adverse effects, interstitial
pneumonitis is the most common presentation after two or more months of
treatment, particularly in individuals over 60 years old with
preexisting lung disease and whose daily amiodarone dosage exceeds 400
mg could occur.
Most of these effects occur due to the accumulation of amiodarone
metabolite so it rarely manifests in the early stage of administration
like in our case.
Interstitial pneumonitis due to amiodarone toxicity is characterized by
the sudden onset of nonproductive cough, dyspnea, and less likely
malaise and fever could be seen. Our case also presented with abrupt
onset of mentioned symptoms which could not be explained by pneumonia or
pulmonary edema.
Other rare microorganisms such as fungal infection in immune-competent
individuals were also unexpected.
A negative autoimmune panel was also more compatible with amiodarone
pneumonitis diagnosis.
When the clinical diagnosis of amiodarone-induced interstitial
pneumonitis is questionable, flexible bronchoscopy with (BAL) is done.
This procedure is more beneficial in excluding other differential
diagnoses.
Despite chronic amiodarone pneumonitis which lipoid cells are more
likely to be seen in pathology in acute amiodarone pneumonitis BAL
investigation, alveolar hemorrhage is more probable to be detected.
[6]
So we can conclude that the absence of lipoid macrophages in BAL is not
supported by excluding the diagnosis of amiodarone pneumonitis and
clinical and radiologic features such as abrupt worsening dyspnea and
cough, administering a high dosage of amiodarone, Exclusion of lung
infection and hypersensitivity pneumonitis, and New ground glass on
chest radiography are key features for diagnosis of early amiodarone
pneumonitis.
Even if our patient had the chance for the BAL it is not the gold
standard for diagnosing amiodarone pneumonitis and as mentioned in
previous studies only 50 % of patients with amiodarone lung injury
manifest with lipoid macrophages in BAL, on the other hand these lipoid
cells could be seen in non-toxic patients who are taking amiodarone.
[7]
Previous studies also mentioned that the route of administration might
be another factor contributing to acute amiodarone pneumonitis like our
reported case, patients who received amiodarone 150mg IV in less than an
hour, followed by exceeding dose of 1000mg IV in a day, Amiodarone
metabolites can accumulate more rapidly in lungs. [8]
On the other hand, some studies believe that acute oxidant lung injury
also plays a major role in amiodarone lung injury in the acute
phase.[9]
Treatment of amiodarone pneumonitis consists primarily of cessation of
amiodarone and, in severe cases, initiating systemic glucocorticoids
(prednisone 40 to 60 mg per day or methylprednisolone 500 to 1000 mg/day
intravenously in severe cases) is recommended. [10]
It is reasonable not to administer antiarrhythmic with similar structure
in amiodarone lung injuries such as Dronedarone and a personalized
approach for each patient is recommended especially in the elderly
patient with underlying lung diseases such as previous severe COVID-19
which lead to permanent lung injury. [11-15]
Acute amiodarone-related interstitial pneumonitis is a rare and more
aggressive form of the disease, most often occurring in critically ill
and post-surgery patients. Acute respiratory distress syndrome (ARDS )
and alveolar hemorrhage are the most common pattern of amiodarone
pneumonitis, our case also encountered ARDS despite corticosteroid
treatment. [16 17]
Conclusion :
In brief, our challenging case illustrates the difficulties in the
diagnosis of acute amiodarone pneumonitis which should be considered as
a differential diagnosis of ARDS causes especially in patients whose
other related diagnoses are excluded and who had a history of receiving
a high dosage of intravenous amiodarone.