Which medical condition can cause skin thickening and yellowish discoloration?

Xanthomas are a condition characterized by the accumulation of lipids in the skin, leading to the formation of yellowish growths or plaques. This occurs as a result of various underlying conditions, often related to abnormal lipid metabolism, such as hyperlipidemia. The skin thickening associated with xanthomas occurs due to the deposition of cholesterol and other fats in the skin tissue, which can manifest as soft, raised, yellowish lesions.

The yellowish discoloration specifically is a hallmark of xanthomas, distinguishing them from other skin conditions that may cause thickening but do not present with the same coloration. Conditions like pleomorphic adenoma, lipoid proteinosis, and neurofibromatosis do not typically exhibit this combination of symptoms, making xanthomas the correct answer regarding both skin thickening and yellowish discoloration.