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Thyroid Biology and Disease

SUN-326 - Pancytopenia secondary to Graves' disease: a case report.

Sunday, June 14, 2026
9:00 AM - 4:00 PM CT
INTRODUCTION
Primary hyperthyroidism is a common endocrine disorder, usually autoimmune, with Graves’ disease as the leading cause. Although its clinical features are well established, hematologic abnormalities such as pancytopenia are rare and infrequently reported in the literature.
CASE PRESENTATION
A 34-year-old woman with a history of hyperthyroidism diagnosed in 2020, previously treated with methimazole with poor adherence and treatment discontinuation in 2023, presented to the Emergency Department in March 2026. She reported an 8-kg weight loss over 3 months, general malaise, hypotension and tachycardia. On physical examination, she exhibited mild agitation, exophthalmos, diffuse goiter, HR 132 bpm, pallor, a holosystolic murmur, fine tremor and lower extremity edema. Initial laboratory studies revealed thyrotoxicosis and pancytopenia: Hb 5.4 g/dL, Hct 16%, MCV 64 fL, MCH 20 pg, Plt 34000/µL, WBC 1900/µL, neutrophils 920/µL, CRC 0.28%, ESR 24 mm/h, TSH 0.00 mIU/mL fT4 4.9 ng/dL, TT4 24.53 µg/dL, fT3 16.12 pg/mL, TT3 5.59 ng/mL & TRAb 67.7 IU/L. Thyroid US demonstrated diffuse enlargement with increased vascularity. Hematology evaluation ruled out infectious and immunologic causes of pancytopenia. No bleeding or organomegaly was documented. Peripheral blood smear showed microcytosis, hypochromia, leukopenia, neutropenia and thrombocytopenia. Iron studies: ferritin 10 ng/mL, transferrin 113 mg/dL TSAT 25%. Immunologic studies (anti-dsDNA, C-ANCA, P-ANCA, C3/C4, ASO, anti-SSA/SSB & anti-Sm) were within normal limits. Vitamin B12 & folate levels were normal. Serologic testing for HIV, VDRL, hepatitis B-C, CMV, HSV I-II, EBV & parvovirus B19 were negative. Flow cytometry showed no evidence of hematologic malignancy, and bone marrow biopsy demonstrated erythroid hyperplasia. Treatment was initiated with red blood cell transfusion, methimazole 30 mg/d, propranolol 40 mg/d, Lugol’s iodine (5 drops every 8 h), and dexamethasone 8 mg every 8 h. The patient tolerated therapy without adverse events and showed clinical improvement. At 72 h after treatment initiation, hematologic improvement was observed: Hb 9.7 g/dL Hto 28% Plt 176000/µL WBC 2300/µL, neu 1200/µL allowing hospital discharge. At one-month follow-up, complete resolution of pancytopenia was documented with significant clinical recovery: Hb 14 g/dL Plt 197000/µL WBC 3200/µL neu 1980/µL,TSH < 0.05 mIU/mL, fT4 1.55 ng/dL TT4 11.5 µg/dL fT3 4.23 pg/mL TT3 1.79 ng/mL.
CONCLUSION
Pancytopenia associated with hyperthyroidism is an uncommon manifestation and should be considered in the differential diagnosis. Bone marrow findings typically include erythroid hyperplasia, as observed in this case. Although thionamides are known to be associated with agranulocytosis, their use may be considered safe under close monitoring. Prompt antithyroid treatment can lead to complete reversal of hematologic abnormalities.

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