SEEING BLUES ALL AROUND

A CASE OF PROPYLTHIOURACIL-INDUCED CYANOPSIA

Abstract

INTRODUCTION/BACKGROUND
Cyanopsia is a subjective symptom characterized by a bluish appearance of the overall visual field and has been reported among patients taking phosphodiesterase-5 inhibitors. Propylthiouracil (PTU) is a member of the thiouracil group and widely used for the treatment of thyrotoxicosis. Despite being associated with various side effects, such as hepatitis, agranulocytosis, body rash, and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, PTU-related cyanopsia has not been reported.

CASE
In this report, we describe a case of PTU-induced cyanopsia, including the results of biochemical laboratory tests. We also discuss treatment strategies and include literature review. A 33-year-old female presented with palpitations and tremors. Clinically, she appeared anxious with hand tremor and diffuse goiter. Her pulse was regular, and other systemic examinations were unremarkable. Thyroid function tests (TFTs) showed overt hyperthyroidism with suppressed thyroid-stimulating hormone (TSH) levels (<0.008 miu/L) and high free T4 levels (55.9 pmol/L). She was treated for Grave’s disease with carbimazole but developed significant urticaria. PTU was then introduced, but she developed a bluish appearance of her surrounding vision right after the second dose. The symptoms subsided after one day of discontinuing PTU. Re-challenging with PTU at a lower dose also resulted in a similar effect. Eye assessment by ophthalmology was normal. She was then given propranolol and cholestyramine to control her thyroid status. Definitive treatment with radioactive iodine will be administered once her thyroid function improves. PTU is one of the mainstay oral medications for hyperthyroidism and is generally well-tolerated. However, PTU-induced cyanopsia may limit oral treatment options, although the phenomenon appears reversible after stopping medication, regardless of the dose. It may cause significant distress and lead to discontinuation of treatment.

CONCLUSION
We report here, the first known case of PTU-induced cyanopsia.