Background <p>Myxedema coma, a life-threatening complication of severe hypothyroidism, is associated with high mortality. Detailed autopsy findings from multiple organs in myxedema coma are rarely reported.</p> Case presentation <p>We present the autopsy findings of an 82-year-old man with hypothyroidism who developed myxedema coma despite levothyroxine treatment. The patient had been under the added stress of trauma and cold exposure before developing a myxedema coma. He exhibited severe hypothermia, hypotension, and reduced thyroid hormone levels. Despite intensive treatment, he died six days after admission. Autopsy revealed pericardial and pleural effusions, and histological evidence of edematous adipose tissue infiltration containing mucopolysaccharides in multiple organs, including the heart, thyroid, pancreas, and kidneys.</p> Conclusions <p>This case highlights that both trauma and cold exposure can serve as critical triggers for myxedema coma, underscoring the importance of proactive management in hypothyroid patients at risk. These risk factors should be carefully considered in clinical practice to prevent severe complications. Our autopsy findings provide the first evidence that myxedema can manifest not only in subcutaneous tissue but also in internal organs, expanding the understanding of its pathophysiology. These insights may contribute to improved prevention and management of myxedema coma, offering a deeper understanding of this life-threatening condition.</p>