Myxoedema coma is a rare, life-threatening endocrine emergency representing the most severe form of hypothyroidism. We present the case of a South Asian woman in her early 70s admitted with generalised oedema, chest pain, general malaise, and reduced appetite. Initially treated as decompensated heart failure, she deteriorated with hypothermia, hypotension, bradypnea, and reduced consciousness, requiring intensive care admission and intubation. Thyroid function testing revealed profound hypothyroidism (TSH 67 mU/L, T4 <2 pmol/L), confirming myxoedema coma. She received intravenous liothyronine and levothyroxine with clinical improvement. This case highlights the noteworthy phenomenon of cold hypercapnia alongside highlighting the diagnostic challenges of myxoedema coma, which may mimic or exacerbate cardiac and respiratory failure. Clinicians should maintain a high index of suspicion in at-risk patients, as delayed recognition and treatment significantly increase mortality.

Basit Khan is a medical doctor who graduated with an MD from Plovdiv Medical University, Bulgaria. He completed his internship and subsequent clinical training at University Hospitals of Leicester (UHL), UK. He is currently working as a Paediatrics ST1 Resident at Alder Hey Children’s Hospital, Liverpool, UK. He has presented his research and clinical work through multiple oral and poster presentations at international conferences and has published several papers in peer-reviewed medical journals. His academic interests include paediatrics, nephrology, clinical research, quality improvement, and medical education.