<prompt> Skin pigmentation resembling rail road tracks seen inMarijuanaOpiumBarbituratesAlcohol  <response>: Chronic opium poisoning They have dry skin with needle puncture marks and sometimes masked by tattooing. Abscesses and thrombosed veins may be seen. I. V users may develop pigmentation and scars on front of the elbow called railroad tracks. Drug addicts may tattoo this area to mask the scars. Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 489 