7605 Patient Suffering from Pancytopenia Secondary to Methimazole in the Setting of Hyperthyroidism

Abstract Disclosure: J. Seidenberg: None. V. Gupta: None. M. Ansari: None. Methimazole induced agranulocytosis is a rare but significant adverse effect of using thalidomide to treat Hyperthyroidism. Agranulocytosis is defined as a severe selective neutropenia associated with some drugs including opioids and specifically Methimazole. The risk has been found to be high in elderly population and those with blood dyscrasias and cross over from immunologic disorders. Patient is a 79 year old F with a PMH of hyperthyroidism started a month prior on Methimazole. While presenting to the endocrinology clinic for a follow up visit, Patient started having palpitations and lightheadedness, slurring of speech with left sided lower limb weakness and AMS and was found to be hypotensive with resolution of symptoms and neurological signs after fluid resuscitation. She was founfd to have undetectable TSH and Free T4 of 90.8-1.2ng/dL) . She was sent to the ED found to have septic shock with positive blood cultures of pseudomonas and drop in WBC from 6400 one month before to 700 (4000-11,000/mcL), an ANC of 0 (2,500-6,000 /mcL)and severe thrombocytopenia progressing from 235,000 on admission to 61,000 (150,000-450,000) on day 4. The patient was treated with antibiotics IV cefepime and IV Doxycycline. The patient was monitored off methimazole with daily CBCs, daily T3 and T4. Patient was transferred to the ICU for closer management due to septic shock. Patient improved with steady increase in ANC and WBC and was discharged home. Agranulocytosis in the setting of Methimazole use is a life-threatening rare side effect. The resultant decreased neutrophils count leading to an immunocompromised state increases risk of sepsis and shock as seen in this case. Patients who develop this side effect should immediately stop their methimazole, be monitored in the hospital for improvement in symptoms and WBC count. They should never be placed back on thalidomides due to increased future risk of agranulocytosis and while hospitalized be checked daily for T3/T4 and if elevated, should be administered cholestyramine to prevent rebound hyperthyroidism. Presentation: 6/2/2024