Introduction
Ochronosis is a rare condition caused by the accumulation of
homogentisic acid in the connective tissues throughout the body. This
accumulation results in the discoloration of tissues to a blue-yellow
hue. This can be seen in the sclera of the eyes1,
nails2, bones3,
skin2-5, thyroid gland6, substantia
niagra6, coronary arteries6 and
cardiac valves6. This discoloration makes for
interesting physical examination findings. The associated differential
diagnosis is quite narrow. Causes of ochronosis are either exogenous or
endogenous. Those that are exogenous include chemical exposure or
ingestion, whereas endogenous causes include inborn errors of
metabolism.