A man with well-demarcated, erythematous and scaly plaques over sun-exposed sites

CASE HISTORY, EXAMINATION AND INVESTIGATION FINDINGS

A 52-year-old male presented with the complaints of itchy and reddish scales over both arms, hands and feet for 1 week. He was a chronic alcoholic for the past 25 years. There was no history of any drug intake for prolonged duration, jowar and maize as staple diet, abdominal pain, constipation, diarrhea or any major gastrointestinal surgeries. On examination, there was symmetrical involvement of extensor surface of arms and dorsal aspect of hands and feet in the form of well-demarcated erythematous to hyperpigmented thick scaly plaques with sparing of photoprotected areas [Figures 1 and 2]. On mucosal examination, icterus was present [Figure 3], oral mucosa was healthy. Hair and nails were normal. The patient was well oriented to time, place and person. Neurological examination showed no abnormalities. Laboratory investigations showed dimorphic anemia, raised bilirubin levels and transaminitis.

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Figure 1:

Well-demarcated, erythematous to hyperpigmented and scaly plaques limited to extensors of both arms with characteristic sparing of photoprotected sites.

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Figure 2:

Hyperpigmented and scaly plaques over dorsal aspect of feet.

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Figure 3:

Scleral icterus.

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WHAT IS YOUR DIAGNOSIS?

Answer:

Pellagrous dermatitis

DISCUSSION

Pellagra is caused by deficiency of niacin or its precursor tryptophan.^[1] Pellagra is classified as primary pellagra which results from inadequate niacin or tryptophan intake and secondary pellagra which results from inability of body to use niacin or tryptophan due to various factors such as drugs, alcoholism, malabsorption syndromes, HIV and malignancies.^[2] Pellagra is characterized by dermatitis, dementia, diarrhea and eventually can cause death if left untreated. Pellagrous dermatitis manifests as bilaterally symmetrical and well-demarcated erythematous rash over sun-exposed areas which gradually progresses to erythematous to hyperpigmented, scaly and leathery plaques. It can also present as a well-demarcated hyperpigmented, scaly and collar-shaped band encircling neck known as ‘Casal’s necklace.’^[3] The WHO recommends 300 mg of oral niacin or nicotinamide supplementation per day or 100 mg in three divided doses orally to be given for 3–4 weeks.^[4] Being a rare disorder nowadays, dermatologist should keep a suspicion of pellagrous dermatitis while dealing with a photosensitive rash as mere niacin supplementation can cure this dermatitis.