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Miscellaneous dermatology

Disorders of pigmentation key points test

Generalised pigmentation may be caused by: # Exposure to a Wood’s lamp #! Melanocyte stimulating hormone # Diabetes insipidus #! Haemochromatosis Explanation: Generalised pigmentation may arise due to excessive circulating melanocyte stimulating hormone in Addison's disease, in haemochromatosis and as a sign of metastatic melanoma. A Wood's lamp is used to evaluate pigmentation. It is low-powered and produces long wavelength UVA so does not result in tanning. Localised pigment may be due to: #! Melanin #! Keratin #! Haemosiderin #! Cinnabar Explanation: Localised pigment may be due to melanin, keratin, haemosiderin or exogenous deposits from tattooing or drugs. Postinflammatory pigmentation: *! May follow clearance of psoriasis * Is unusual in lichen planus * Improves with sun exposure * Commonly affects individuals with skin phototype 1 Explanation: Postinflammatory pigmentation follows injury or inflammatory disorder of the skin and is particularly marked in lichen planus. It is mostly observed in skin phototypes 4-6 and is more prominent after sun exposure. Hyperpigmentation is characteristic of: # Pityriasis alba # Mild contact allergic dermatitis #! Capillaritis #! Poikiloderma of Civatte Explanation: Hyperpigmentation may arise in pityriasis versicolor, phytophotodermatitis, melasma, poikiloderma of Civatte and capillaritis. Treatment of hyperpigmentation may include: #! SPF30+ sunscreen #! Topical retinoids # Cosmetic camouflage # Phototherapy Explanation: Treatment of hyperpigmentation may include broad-spectrum sunscreen, hydroquinone, topical steroids, azelaic acid, glycolic acid and topical retinoids. Cosmetic camouflage may be the most appropriate option for some patients. Hypopigmentation is characteristic of: #! Pityriasis alba #! Third degree burns # Hyperpituitarism #! Leprosy Explanation: Hypopigmentation may arise in hypopituitarism, pityriasis alba, pityriasis versicolor, after inflammation including burns, vitiligo, lichen sclerosus and leprosy. Vitiligo may be associated with: #! Hypothyroidism # Psoriasis #! Sunburn # Alopecia mucinosa Explanation: Vitiligo is an autoimmune disease associated with thyroid disease, diabetes mellitus, pernicious anaemia and alopecia areata. It may be precipitated by injury including sunburn. There is no known association with psoriasis.