Fig. 2
From: COVID-19-associated gastrointestinal and liver injury: clinical features and potential mechanisms
Patients with severe COVID-19 develop facial blackness and dull skin after recovery. Liver injury during COVID-19 is mainly responsible for these special manifestations. Three possible mechanisms are presented: (1) iron in the damaged liver drains into blood vessels. The blood with high iron level can lead to a blackening of the face once it supplies to the facial skin; (2) estrogen cannot be metabolized in the damaged liver. An increase in estrogen in the blood eventually causes an increase in conversion of tyrosine to melanin; (3) when liver function is impaired, adrenocortical function is hypoactive and melanocyte-stimulating hormone increases
