C i.e. Uicaria pigmentosa Darrier sign is development of uicaria and erythema around the pale-yellow to reddish-brown macules after mild trauma, including scratching or rubbing of the lesion(2. It is seen mostly (but not always) in uicaria pigmentosa. However, it is not 100% specific for mastocytosis as it is also rarely seen in juvenile Xanthogranuloma and acute lymphoblastic leukaemia of neonates. Uicaria Pigmentosa (UP)/Mastocytosis - Mastocytosis is mast cell hyperplasia in 1 organs: bone marrow, liver, spleen, lymph nodes, gastrointestinal tract and skin. So mast cell activation may produce symptoms like, pruritis, flushing, uication, abdominal pain, nausea, vomiting, diarrhea, musculo skeletal pain, vascular instability, headache and neuropsychiatric difficulties. UP (a type of cutaneous mastocytosis) is the most common manifestation of mastocytosis, both in adults & children. - Numerous pale yellow tan to reddish brown monomorphic macules or slightly raised papules develop in a symmetrical distributions anywhere on the body with generally less involvement of the sun exposed areas, with the highest concentration usually being on the trunk and thighsQ. Also generally spared (or less involved) are face, scalp, head, palms & soles. - The edges of lesion are not completely sharp. It is not uncommon for lesion to become pigmented, hence name uicaria pigmentosa. - Development of uicaria, erythema & itching around the lesion after mild trauma, including scratching or rubbing of lesionQ is called Darier Sign. It is seen in UP. - Climatic temperature, skin friction, ingestion of hot beverages, spicy foods, alcohol, opioids or other drugs may cause histamine release from mast cells and exacerbate mastocytosis - 3 types/ forms of UP are Juvenile type develop mostly in P, year of life and usually remits spontaneously during adolescence Adult papular type persists. Adult telangiectasia macularis eruptive perstans of Parker & Weber: in which telangiectatic macules sta to appear, persist and increase in number over the years. Uicarial Vasculitis - An impoant characteristic of uicaria is its transience but rarerly it may stay for days rather than hours & leave a brownish stain - It is due to involvement of small vessels - Vasculitis uicari typically persist longer than 72 hours, where as conventional uicaria often has a duration of less than 24 -48 hours. Fixed drug Erruption - Inflamatory patches appear within hours at the same sites on every occasionQ the drug is administered Leave pigmentation - Common drugs are dapsone, tetracycline, sulfonamides, mefenimic acid.