Casal collar

{{Short description|Medical condition}}

{{Infobox medical condition

| name = Casal collar

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| image = PHIL 3757 lores.jpg

| caption = A boy with casal collar caused by pellagra

| pronounce =

| field = Dermatology

| symptoms = Redness and darkening around neck

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| causes = Pellagra

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| differential = Seborrheic dermatitis

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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.{{cite book|last=Johnstone|first=Ronald B.|title=Weedon's Skin Pathology Essentials|chapter-url=https://books.google.com/books?id=NTE_DAAAQBAJ&pg=PA65|year=2017|publisher=Elsevier|isbn=978-0-7020-6830-0|edition=2nd|page=65|chapter=4. Psoriasiform reaction pattern}} It becomes prominent following exposure to sun, and can be itchy with a burning feeling and pain.{{cite book |last1=James |first1=William D. |last2=Elston |first2=Dirk |last3=Treat |first3=James R. |last4=Rosenbach |first4=Misha A. |last5=Neuhaus |first5=Isaac |title=Andrews' Diseases of the Skin: Clinical Dermatology |date=2020 |publisher=Elsevier |location=Edinburgh |isbn=978-0-323-54753-6 |pages=479-480 |edition=13th |chapter-url=https://books.google.com/books?id=UEaEDwAAQBAJ&pg=PA479 |language=en |chapter=22. Nutritional diseases}} It can blister and weep, and turn into thick dark skin, with a coppery hue. If prolonged, the skin becomes thin, dry and smooth.

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

Casal collar is named after Gaspar Casal.{{cite book |last1=Stedman |first1=Thomas Lathrop |title=Stedman's Medical Eponyms |date=2005 |publisher=Lippincott Williams & Wilkins |isbn=0-7817-5443-7 |page=126 |edition=2nd |url=https://books.google.com/books?id=isqcnR6ryz0C&pg=PA126 |language=en}}