<prompt> Casals necklace is seen in the following diseaseBeri-BeriScurvyPernicious anemiaPellagra  <response>: The Casal necklace is an erythematous pigmented skin rash in the distribution of a broad collar dermatomes C3 and C4. It is seen in patients with pellagra. It occurs as a result of niacin vitamin B-3 deficiency. Pellagra is a disease characterised by diarrhoea, dermatitis and dementia. Ref : Biochemistry by U. Satyanarayana 3rd edition Pgno : 138-141 