Serum bilirubin measurement is necessary to accurately distinguish jaundice from carotenemia. A 59.8-y old Japanese male showed symptoms of yellow skin pigmentation as a result of β-carotenemia. Diagnostic laboratory results indicated elevated levels of serum muscle enzymes (aspartate aminotransferase, lactate dehydrogenase, and creatine kinase), but normal levels in liver function tests (alanine aminotransferase and direct bilirubin). The laboratory results indicated hypothyroid myopathy. Moreover, although the patient did not show significant abnormalities in liver function tests, the serum level of total bilirubin (TBIL) measured by bilirubin oxidase method was markedly increased beyond the upper limit of normal. Fundamental experiments revealed that the bilirubin oxidase method had a positive interference by β-carotene. These findings suggested that hyper β-carotenemia could have caused the falsely elevated serum TBIL levels in the patient.
Keywords: bilirubin; carotene; hypothyroidism; liver disease; myopathy; yellowish skin pigmentation.