Niacin deficiency classically causes the 4 D's: Dermatitis, Diarrhea, Dementia and Death.
Skin photosensitivity and rash.  Erythematous and scaly.  May be mistaken for sunburn.
secondary to UV damage and decreased repair and hence the desquamation, keratosis and erythema is most common in sun-exposed skin
"Casal's Necklace." Reddish rash surrounding the neck, and on the hands and feet.  This is a photosensitivity rash in the exposed areas of the neck.  Originally described by Gaspar Casal in 1735.
GI symptoms
secondary to decreased cell turnover
Neurological symptoms<unk>  encephalopathy," depression, anxiety, altered mental status, hallucinations, delusions, affective disorders, cognitive dysfunction.
secondary to UV damage and decreased repair and hence the desquamation, keratosis and erythema is most common in sun-exposed skin
"Casal's Necklace." Reddish rash surrounding the neck, and on the hands and feet.  This is a photosensitivity rash in the exposed areas of the neck.  Originally described by Gaspar Casal in 1735.
secondary to decreased cell turnover<unk>  encephalopathy," depression, anxiety, altered mental status, hallucinations, delusions, affective disorders, cognitive dysfunction.
Niacin deficiency is often associated with chronic alcohol use secondary to nutritional deficiency and malabsorption.
Pellagra
Acute generalized exanthematous pustulosis
Strawberry tongue
Allergic reaction
Paronychia
Aphthous stomatitis
Body stuffing
Atopic dermatitis