Funny Colours View GlobalSkinAtlas for Images
Excluding red and skin colors we will look at lesions that are an uncommon colour.
Yellow lesions Yellow lesions look yellow because of fat, sebaceous material, degraded elastic tissue, altered keratin, carotene, jaundice pigment or drugs. At one stage resolving bruises go through a yellow phase.
Yellow papules or nodules are Xanthomas, Xanthoma disseminatum , xanthogranulomas including necrobiotic, Sebaceous hyperplasia and other sebaceous tumours, Gouty tophi around elbows and knees and Xanthelasma on eyelids.
Yellow skin consider carotene pigmentation of palms and soles, jaundice from any cause and drugs such as quinacrine.
Yellow skin consider carotene pigmentation of palms and soles, jaundice from any cause and drugs such as quinacrine.
Rarer conditions include Nodular amyloidosis, Colloid milium, Eruptive Xanthomas, and Pseudoxanthoma elasticum with yellow papules and chicken skin plaques on the neck. Nevus lipomatosis is usually seen at birth on the buttocks. Sebaceous nevus is usually in the scalp or on the forehead and also present at birth.
I think Site is a good way of separating out yellow lesions
Forehead - Sebaceous hyperplasia, Sebaceoma, Juvenile Xanthogranuloma, Sebaceous nevus
Eyelids - Xanthelasma, Necrobiotic Xanthogranuloma, Syringomas, Sebaceous carcinoma
Face - Sebaceous hyperplasia, JXG , Colloid milium
Neck - PXE, Severe solar elastosis, Plane xanthomas
Flexures - PXE , Xanthoma disseminatum , Plane xanthomas
Scalp - Sebaceous nevus , JXG ,
Buttocks - Eruptive xanthomas
Shin - Necrobiosis lipoidica
Dermatoscopic features can help diagnose some of these yellow papular lesions.
Dermoscopic decision algorithm (quick)
Is the yellow homogeneous and lobulated? → Xanthoma group
Is the yellow orange with a “setting sun” pattern? → JXG
Is there a central dell + crown vessels? → Sebaceous hyperplasia
Are there milia‑like cysts or comedo‑like openings? → SK
Is the yellow chalky white? → Calcinosis cutis or Gout
Is the background red with string‑of‑pearls vessels? → Clear cell acanthoma
Purple lesions
Purple lesions are that colour because of altered or venous blood , overgrowth of blood vessels or infiltrates of neutrophils or lymphocytes into the skin. Consider therefor haemangiomas, angiosarcomas, Kaposi's sarcoma, port wine stains or other vascular malformations, vasculitis with leaked blood cells, lymphocytoma, lymphoma, and the plaques and nodules of Sweet's syndrome where the infiltrating cells are lymphocytes. Sarcoidosis can also have a purple colour in the skin. Better also consider drugs giving a lichenoid drug reaction eg Thiazides and of course Lichen planus itself with itchy papules at the wrists and lower legs.
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Green lesions
There are not many green lesions in the skin. Copper bracelets can cause green staining under them. Thereafter it would need to be exogenous pigmentation from a dye. Do not know any drugs causing a generalised green skin colour.
Blue lesions
Things appear blue in the skin if melanin is in the upper dermis or below. It has something to do with light scattering by the tissues. The same melanin higher in the epidermis shows as black. Venous blood is also blue as is the drug minomycin or clofazimine when they are deposited in the skin. Blue papules are blue nevi , melanoma metastases, leukaemic deposits or some lichen planus papules. Blue nodules in neonates are due to severe viral infections with extramedullary haematopoesis or neuroblastoma metastases!
Cyanosis makes you blue as well!
Grey lesions
Again consider drugs such as Minocycline and post inflammatory hyperpigmentation particularly with fixed drug reactions and lichen planus. It is usually due to melanin in melanophages in the dermis.
