Routine neonatal urine screening has indicated
that many individuals with this defect are asymptomatic. Affected patients
develop a photosensitive skin rash, usually beginning in children 3 to 9
years old (but may present during the neonatal period). Typically, after
sunlight exposure, the skin reddens. A dry, scaly, well-marginated eruption
may develop on the face and other light-exposed areas. With time,
pigmentation changes may become definitive. More rarely, episodes of
cerebellar ataxia, emotional lability, encephalopathy, and ocular
manifestations occur. The episodes are reversible with treatment, which
consists of nicotinic acid supplementation with a high-protein diet (in
addition to use of creams for protection from sunlight). Exacerbations occur
most often in spring or early summer after exposure to sunlight. They may
be favored by febrile illness, poor nutrition, treatment with sulfonamides,
and emotional stress.