A 65-year-old man presented to the ED after experiencing syncope during a flight. On arrival, his vital signs were stable, including normal oxygen saturation while breathing ambient air. Physical examination revealed normal respiration, the absence of a heart murmur and no lower extremity oedema. Laboratory examination, chest radiography and electrocardiography were unremarkable. The patient reported daily consumption of an unidentified herbal supplement during the COVID-19 pandemic for approximately 2 years, and skin discolouration was noted at present (figure 1).

The photograph taken on the patient’s arrival.

What is the most likely diagnosis?

Argyria

Venous thromboembolism

Eisenmenger syndrome

Acquired methaemoglobinaemia

Answer: A Argyria

Skin grey-blue discolouration can signal …