Patient 6, a young female with a history of androgenetic alopecia presenting with pellagra-like dermatitis secondary to sun exposure, was diagnosed with Hartnup disease (MIM: 234500), caused by compound heterozygous variants in SLC6A19 (p.Asp173Asn, p.Glu519Gly). The gene discussed is SLC6A19; the disease is Hartnup disease.