Pancytopenia in a Patient With Severe Hypothyroidism: A Case Report

Abstract

Abstract Introduction: Hypothyroidism usually affects red blood cell line most commonly seen as normochromic normocytic anemia. We present a unique case of a patient with pancytopenia in the setting of severe hypothyroidism, which improved following IV thyroid hormone replacement. Case: An 85-year-old female with history of type II diabetes mellitus and hypothyroidism who was admitted for open reduction and internal fixation (ORIF) of a displaced left femur fracture following a mechanical fall. Patient has a long-standing history of hypothyroidism on replacement with levothyroxine 75 mcg, which was inadvertently discontinued at the nursing home 2 weeks prior to presentation. CBC on admission was notable for pancytopenia with macrocytic anemia with hemoglobin of 6.2 g/dl (baseline of 11), leukopenia with WBC of 4.2 x103/ul and thrombocytopenia with platelet of 77 X 103 /ul. TSH was 83 uIU/mL (reference range: 0.34 - 5.6) and Free T4 was < 0.11 ng/dl (reference range: 0.93 - 1.7). Patient was on the verge of developing myxedema coma as she presented with hypotension with blood pressure of 103/55 mmHg, hyponatremia 133 mmol/L and mild change in mental status. There was no evidence for hypothermia or bradycardia. Presence of a small thigh hematoma on examination partially explained the acute drop in hemoglobin. Iron panel, folic acid and vitamin B12 levels were found to be within normal range. Patient had no active of infection to suggest sepsis and she did not receive any myelosuppressive medication. Rapid replacement with IV levothyroxine was started before proceeding with surgery to prevent development of myxedema coma. Free T4 normalized at 1.05 ng/dl after receiving a total of 700 mcg of IV levothyroxine on day 5 of hospitalization. ORIF was done with no complications. Pancytopenia resolved upon thyroid replacement therapy and she was discharged on her regular dose of levothyroxine 75 mcg daily. Discussion: Most common hematologic abnormality associated with hypothyroidism is normochromic normocytic anemia. Currently, there are less than 10 reported cases of pancytopenia associated with hypothyroidism. The exact mechanism is unclear but proposed hypothesis is transient bone marrow hypoplasia. The most common clinical presentation, as seen in our patient, is profound hypothyroidism with ultimate outcome of myxedema coma. Most of these patients had resolution of pancytopenia following adequate thyroid hormone replacement. Interestingly, all cases have been reported in female patient population. Further research is needed to understand pathophysiology, risk factors, prognosis and the risk of pancytopenia recurrence in patients with severe hypothyroidism. More importantly, hypothyroidism must certainly be entertained as a differential diagnosis of pancytopenia.