Amino acids are building blocks for protein. There are three types of amino acids based on the polarity of the side chain. It includes acidic, basic, and neutral amino acids. Hartnup disease is an autosomal recessive inherited nutritional disorder due to decreased absorption of neutral amino acids from the gut and kidney. It has a wide range of clinical spectrum including neutral aminoaciduria, indicanuria, photosensitive pellagra like skin rash, cerebellar ataxia, anxiety, depression, mild intellectual disability. The clinical symptoms occur intermittently and are influenced by environmental factors, season, stress, and malnutrition. Some patients remain asymptomatic and are diagnosed through routine screening.