An autosomal recessive disorder due to defective absorption of NEUTRAL AMINO ACIDS by both the intestine and the PROXIMAL RENAL TUBULES. The abnormal urinary loss of TRYPTOPHAN, a precursor of NIACIN, leads to a NICOTINAMIDE deficiency, PELLAGRA-like light-sensitive rash, CEREBELLAR ATAXIA, emotional instability, and aminoaciduria. Mutations involve the neurotransmitter transporter gene SLC6A19.