Casal collar

The Casal collar or Casal necklace is a medical sign in which there is a redness and darkening of the skin around the neck, seen in people with pellagra.^[2] It becomes prominent following exposure to sun, and can be itchy with a burning feeling and pain.^[1] It can blister and weep, and turn into thick dark skin, with a coppery hue.^[1] If prolonged, the skin becomes thin, dry and smooth.^[1]

Casal collar
A boy with casal collar caused by pellagra
Specialty	Dermatology
Symptoms	Redness and darkening around neck[1]
Causes	Pellagra[2]
Differential diagnosis	Seborrheic dermatitis[1]

The sign is caused by a lack of the niacin (vitamin B₃).^[1] Seborrheic dermatitis may appear similar.^[1]

Casal collar is named after Gaspar Casal.^[3]