Exogenous ochronosis: the failure of depigmenting creams.

Exogenous ochronosis (EO) is an entity that manifests as black-bluish or grayish-brown cutaneous hyperpigmentation, which is a consequence of the deposition of ochronotic pigment with characteristic banana-like morphology between the collagen fibers of the dermis. Both the clinical presentation and histopathology appearance are superimposable with endogenous ochronosis or alcaptonuria, a hereditary disease in which ochronotic pigment deposition occurs at a multisystemic level. The most frequent cause of EO is the use of facial depigmenting creams containing hydroquinone, a common practice among women with high phototypes.

Endogenous ochronosis: when clinical suspicion prevails over histopathology.

Endogenous ochronosis (EO) or alkaptonuria is an inherited autosomal recessive disease caused by the insufficiency of the enzyme homogentisic acid dioxygenase. This disturbance causes an accumulation and increased renal excretion of homogentisic acid (AHG), which manifests as dark urine when it oxidizes on contact with air. Other clinical manifestations of OE are the result of the deposit of AHG in the form of ochronotic pigment at the level of collagen in the skin and cartilage, where it causes blue-gray cutaneous hyperpigmentation, degenerative arthropathy, valvular disease, and other multisystem effects.