Hyperpigmentation Disorders - Dermatology

Overview

Freckle	Caused by normal number of melanocytes but increased melanin within basal keratinocytes Darkens with sun exposure
Lentigo	Pigmented macule caused by melanocyte hyperplasia Does not darken with sun exposure
Common mole	A benign tumor derived from melanocytes
Blue nevus	Form of common mole, a benign tumor derived from melanocytes Black and blue nodule usually present at birth Often mistaken for melanoma
Spitz nevus	Form of common mole, a benign tumor derived from melanocytes Red-pink nodule Often seen in children Confused with hemangioma
Dysplastic nevus	Atypical, irregularly pigmented lesion Increased risk of transformation into malignant melanoma
Dysplastic nevus synrome	Autosomal dominant inherited disease
Melasma	Mask-like hyperpigmentation seen in pregnancy on the face Sunlight accentuates, so avoid sunlight Treat with hydroquinone cream Usually fades postpartum
Xanthoma	Yellowish papules Often accumulations of histiocytes Can be idiopathic or associated with hyperlipidemia Called xanthelasma when on eyelids Treat by decreasing lipidemia Surgically excise as needed
Acanthosis nigricans	Black, velvety plaques on flexor surfaces Seen in obesity and endocrine disorders, namely insulin resistance Can mark underlying malignancy
Seborrheic keratosis	Black or brown benign plaques Appear to be stuck on skin "Coin lesions" Commonly seen in the elderly Runs in families Can be mistaken for melanoma Liquid nitrogen freezing, if not too many