Carotenemia: This condition is caused by an excess of carotenoids in the blood, often due to a diet rich in carrots, sweet potatoes, or other carotenoid-containing foods. It leads to a yellow or orange discoloration of the skin, particularly on the palms, soles, and mucous membranes, but can also appear brown-orange depending on the individual's skin tone and the amount of carotenoids consumed.

Jaundice: While typically associated with a yellow discoloration, in some cases, especially with mixed bilirubin elevations (conjugated and unconjugated), the skin can take on a brownish hue, particularly in areas like the palms and soles. Jaundice is a sign of liver dysfunction or a hemolytic disorder.
Argyria: Caused by exposure to silver or silver compounds, argyria leads to a bluish-gray discoloration of the skin and mucous membranes. However, in some cases, especially when the exposure is to certain silver compounds, the discoloration can appear more brown or orange, particularly in sun-exposed areas or the mouth.
Hemochromatosis: This genetic disorder leads to excessive iron absorption, which can cause skin pigmentation changes, including a bronze or brown discoloration, especially in sun-exposed areas and potentially on the palms and soles.

Wilson's Disease: An inherited disorder that causes copper to accumulate in the body, particularly in the liver, brain, and other vital organs. It can lead to liver disease, neurological symptoms, and psychiatric problems. Kayser-Fleischer rings (copper deposits in the cornea) are a hallmark, but skin discoloration can also occur.
Addison's Disease: A rare disorder of the adrenal glands where not enough cortisol and aldosterone are produced. One of the symptoms can be hyperpigmentation, which might appear as brown or darkened skin areas, including the palms, soles, and mucous membranes.

Porphyrias: A group of disorders that result from a buildup of porphyrins, which are compounds required for hemoglobin production. Some types of porphyria can cause blistering, scarring, and changes in skin pigmentation, potentially leading to a brown or orange discoloration in affected areas.
Minocycline-induced Hyperpigmentation: A rare side effect of the antibiotic minocycline, which can cause blue-black, brown, or gray discoloration in various parts of the body, including the skin and mucous membranes.