Ochronosis is a syndrome caused by the accumulation of homogentisic acid in connective tissues. The condition was named after the yellowish (ocher-like) discoloration of the tissue seen on microscopic examination. Macroscopically, though, the affected tissues appear bluish-grey because of a light-scattering phenomenon known as the Tyndall effect. The condition is most often associated with alkaptonuria, but can occur from exogenous administration of phenol complexes such as hydroquinone. It was first described by Rudolf Virchow in 1865. Types
The two types of ochronosis are endogenous and exogenous. The endogenous variety is an autosomal-recessive disease, known as alkaptonuria, that is caused by a lack of homogentisate oxidase enzyme. Exogenous ochronosis is an avoidable dermatitis that can be caused by the topical application of compounds such as hydroquinone or phenols. It was first seen in 1912, when a patient who used phenol on a leg ulcer was found by Beddard and Plumtre to have this condition. Hydroquinone-induced exogenous ochronosis was found in 1975 by Findlay, who observed the condition in patients who used skin lightening creams containing the compound.The three clinical stages of exogenous ochronosis are:
Erythema and mild hyperpigmentation
Hyperpigmentation and "caviar-like" lesions
Papulonodular lesions

Signs and symptoms
Skin: The pigment is deposited throughout the skin, but only becomes apparent in certain locations, where the concentration is great enough to be seen clinically. This usually occurs in areas where connective tissue is thick (joints, tympanic membrane) or close to the surface of the skin (thenar and hypothenar eminences and the sides of the fingers).
Pathophysiology
Any obstruction of the venous vasculature of the liver is referred to as Budd–Chiari syndrome, from the venules to the right atrium. This leads to increased portal vein and hepatic sinusoid pressures as the blood flow stagnates. The increased portal pressure causes increased filtration of vascular fluid with the formation of ascites in the abdomen and collateral venous flow through alternative veins leading to esophageal, gastric and rectal varices. Obstruction also causes centrilobular necrosis and peripheral lobule fatty change due to ischemia. If this condition persists chronically what is known as nutmeg liver will develop. Kidney failure may occur, perhaps due to the body sensing an "underfill" state and subsequent activation of the renin-angiotensin pathways and excess sodium retention. Diagnosis
When Budd–Chiari syndrome is suspected, measurements are made of liver enzyme levels and other organ markers (creatinine, urea, electrolytes, LDH).Budd–Chiari syndrome is most commonly diagnosed using ultrasound studies of the abdomen and retrograde angiography. Ultrasound may show obliteration of hepatic veins, thrombosis or stenosis, spiderweb vessels, large collateral vessels, or a hyperechoic cord replacing a normal vein. Computed tomography (CT) or magnetic resonance imaging (MRI) is sometimes employed although these methods are generally not as sensitive. Liver biopsy is nonspecific but sometimes necessary to differentiate between Budd–Chiari syndrome and other causes of hepatomegaly and ascites, such as galactosemia or Reyes syndrome. Evaluation for a JAK2 V617F mutation is recommended. Treatment
A minority of patients can be treated medically with sodium restriction, diuretics to control ascites, anticoagulants such as heparin and warfarin, and general symptomatic management.