Bone marrow granulomas possibly associated with amiodarone

Increased Risk of Antithyroid Drug Agranulocytosis Associated with Amiodarone-Induced Thyrotoxicosis: A Population-Based Cohort Study

BACKGROUND

Agranulocytosis occurs in 0.2-0.5% of patients treated with the antithyroid drugs (ATDs) methimazole and propylthiouracil. The objectives of this study were to evaluate the risk of ATD-related agranulocytosis in patients with amiodarone-induced thyrotoxicosis (AIT), and to compare it with the agranulocytosis risk in patients with thyrotoxicosis due to other etiologies treated with ATDs.

METHODS

This was a retrospective cohort study. Participants were 14,781 adult patients with thyrotoxicosis, newly treated with an ATD between January 1, 2002, and December 31, 2015. Among them were 593 patients treated by ATDs due to AIT. The main outcome measures were incidence rates and crude and adjusted hazard ratios using univariate and multivariable Cox regression models for ATD-related agranulocytosis within one year of treatment initiation, in association with AIT.

RESULTS

Agranulocytosis occurred in 28 (0.19%) of patients newly treated with methimazole or propylthiouracil during the first year of follow-up. Of these 28 patients, 8/593 (1.35%) were AIT patients and 20/14,188 (0.14%) were thyrotoxic patients that was not AIT related (p < 0.001). Incidence rates were 22 (9.47-43.36) cases/1000 person-years of follow-up in AIT, and 1.79 (1.09-2.76)/1000 person-years of follow-up in non-AIT thyrotoxicosis (p < 0.0001). In univariate Cox regression analysis, risk for ATD agranulocytosis associated with AIT was 9.71 (4.28-22.05) compared to the risk in non-AIT thyrotoxicosis. In a multivariable model, adjusting for age, sex, body mass index, smoking history, year of cohort entry, diabetes mellitus, hypertension, renal failure, beta blockers, calcium channel blockers, anti-aggregants, and dose of ATDs, the risk associated with AIT was 5.70 (2.14-15.21). In a model adjusted for a propensity score to receive amiodarone, risk for ATD agranulocytosis associated with AIT was 6.32 (1.22-32.70).

CONCLUSIONS

ATD use is associated with a higher risk for agranulocytosis in patients with AIT.

Amiodarone-induced bone marrow granulomas: an unusual cause of reversible pancytopenia

Bone marrow infiltration by granulomas rarely presents with cytopenias and is usually a result of atypical infections, lymphomas, or sarcoidosis. Drugs are also an important but often overlooked causal agent of bone marrow granulomas. Although rare, amiodarone has been associated with bone marrow granuloma formation. This case report describes a 73-year-old male who presented with pancytopenia during a preoperative evaluation. Amiodarone therapy was suspected to be the causal agent after diagnostic evaluation and exclusion of other causes. After cessation of amiodarone, the patient's pancytopenia gradually resolved over a period of several months. Our report illustrates an often overlooked yet important cause of reversible pancytopenia owing to suspected amiodarone-induced bone marrow granuloma formation, and guides clinicians in an expected timeline for blood count improvement after cessation of this drug.

Unexplained bone marrow granulomas: is amiodarone the culprit? A report of 2 cases

Granulomas in the bone marrow are usually caused by infectious or hematological diseases, and drugs are only rarely implicated as causative agents. Recent reports have drawn attention to the role of amiodarone in the etiology of bone marrow granulomas. We report two cases of amiodarone-induced bone marrow granulomas in patients being investigated for refractory anemia and pancytopenia, respectively. Since both patients had life-threatening arrhythmias, discontinuation of the drug followed by rechallenge was not possible. Both patients did well in spite of continued amiodarone therapy, indicating that the underlying hematological illnesses were unrelated to the granulomas. Amiodarone should be considered as a possible cause of bone marrow granulomas after the exclusion of other causes. Continued use of amiodarone after granuloma formation must be dictated by the underlying cardiac condition.