THE SILENT ATTACK

PANCYTOPENIA AS AN ATYPICAL PRESENTATION OF HASHITOXICOSIS PHASE OF HASHIMOTO'S DISEASE

Abstract

INTRODUCTION/BACKGROUND
Autoimmune thyroid disease (AITD) has been linked to cytopenia with hyperthyroidism causing pancytopenia, while hypothyroidism is linked with anaemia. However, pancytopenia rarely occurs in hypothyroidism. We present a case of alternating hyperthyroidism and hypothyroidism presenting initially with pancytopenia.

CASE
A 70-year-old female presented with prolonged fever for three weeks without any other symptoms. Physical examination was normal, but initial blood tests showed cytopenia of all cell lineage with no identified cause. Screening tests for malnutrition, infection, tuberculosis, and connective tissue disease were normal. CECT Thorax Abdomen and Pelvis showed only multiple thyroid nodules. Thyroid function showed hyperthyroidism with TSH levels <0.01 ml/UL, fT4 28pmol/L, elevated antiTG, and anti-TPO, while TSI was normal. Carbimazole 5 mg daily was initiated for hyperthyroidism. Two months later, the patient showed symptoms and signs of hypothyroidism, TSH 57.10 ml/UL and fT4 2.72 pmol/L, consistent with diagnosis of Hashimoto's disease. Carbimazole was discontinued, L-thyroxine replacement initiated. Follow up period noted normalization of thyroid function, but poor recovery of pancytopenia under further evaluation and management by haematologist. Hashimoto’s disease can present with alternating hyperthyroidism known as hashitoxicosis phase, followed by hypothyroid state. Hyperthyroidism-induced pancytopenia is caused by decreased production of haemopoietic cells or increased destruction by immunological mechanisms or hypersplenism. However, the exact mechanism of hypothyroidism-induced pancytopenia is not well understood, but it is thought to be related to the immune system's dysregulation leading to a decrease in the lifespan of certain blood cells.

CONCLUSION
Hashimoto’s disease needs to be considered as a differential diagnosis for pancytopenia. Resolution of pancytopenia is usually achieved after reaching a euthyroid state, but further haematological evaluation may be needed if the condition persists.