What skin manifestation is characterized by dirty, velvety patches often found on the neck in an obese patient?

The skin manifestation characterized by dirty, velvety patches often found on the neck, particularly in obese individuals, is known as acanthosis nigricans. This condition typically presents as thickened, darkened areas of skin that can resemble dirt and is most commonly associated with insulin resistance, obesity, and metabolic syndrome.

Acanthosis nigricans can also occur in association with certain endocrine disorders, such as polycystic ovary syndrome (PCOS) and Cushing's syndrome, but its strong association with obesity and insulin resistance makes it a key finding in such patients. The appearance of these patches is due to epidermal hyperplasia and increased melanin production, which gives the skin its velvety texture and color.

In contrast, hidradenitis suppurativa is a chronic inflammatory condition that leads to painful lumps, abscesses, and sinus tracts primarily in areas where skin rubs together, such as the armpits and groin. Lichen planus is an inflammatory condition characterized by purple, itchy, flat-topped lesions on the skin and mucous membranes, rather than dirty patches. Skin tags are benign, soft growths that appear on the skin, commonly found in areas of friction, but they