A 42-year-old man who recently emigrated from Northern Africa comes to the clinic due to a 1-month history of abdominal pain and watery diarrhea. He has also had a skin rash for the last 2 months that gets worse with sun exposure. In addition, the patient has felt depressed recently and has loss of appetite with mild weight loss. Medical history is notable for latent tuberculosis, for which he is currently taking isoniazid and pyridoxine. The patient takes no other medications and does not use tobacco, alcohol, or illicit drugs. He is vegetarian, and his diet consists mostly of corn and other cereal grains. On examination, there is a pigmented scaly skin rash in the malar distribution of his face, on his neck, and on the back of his hands. He also has mild, diffuse abdominal tenderness. Neurologic examination, including distal sensation and gait, is normal. Liver function tests are normal. Which of the following is the most likely diagnosis?

Question

A 42-year-old man who recently emigrated from Northern Africa comes to the clinic due to a 1-month history of abdominal pain and watery diarrhea.  He has also had a skin rash for the last 2 months that gets worse with sun exposure.  In addition, the patient has felt depressed recently and has loss of appetite with mild weight loss.  Medical history is notable for latent tuberculosis, for which he is currently taking isoniazid and pyridoxine.  The patient takes no other medications and does not use tobacco, alcohol, or illicit drugs.  He is vegetarian, and his diet consists mostly of corn and other cereal grains.  On examination, there is a pigmented scaly skin rash in the malar distribution of his face, on his neck, and on the back of his hands.  He also has mild, diffuse abdominal tenderness.  Neurologic examination, including distal sensation and gait, is normal.  Liver function tests are normal.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d0d7_c0c2_bc81_ad1ab9f7d7cd_MD0003_00 Pellagra ("rough skin" in Italian vernacular) is due to niacin deficiency and is characterized by the "3 Ds": dermatitis, diarrhea, and dementia: Dermatitis is primarily on sun-exposed areas of the body and is characterized by rough, hyperpigmented, scaly skin. Diarrhea is often associated with abdominal pain, nausea, and loss of appetite. Dementia is due to neuronal degeneration in the brain and spinal cord and can lead to memory loss, affective symptoms (eg, depressed mood in this patient), and psychosis. Niacin is present in a broad variety of foods and can be synthesized endogenously from tryptophan. In developing countries, niacin deficiency is seen in populations that subsist primarily on corn products (niacin in corn occurs in a bound, unabsorbable form). In developed countries, it is primarily seen in patients with impaired nutritional intake (eg, heavy alcohol use, chronic illness). Pellagra can also be seen occasionally in those with carcinoid syndrome (due to depletion of tryptophan) or Hartnup disease (congenital disorder of tryptophan absorption). Prolonged isoniazid therapy can interfere with metabolism of tryptophan and occasionally lead to pellagra. (Choice A) Acute intermittent porphyria (AIP) causes abdominal pain, vomiting, and diarrhea, often with neurologic symptoms (eg, agitation, paresthesias, confusion). Although AIP may be triggered by isoniazid, the symptoms are episodic rather than chronic, chronic transaminase elevation is common, and it is more frequent in women than in men. (Choice B) Isoniazid hypersensitivity can present as hives (maculopapular rash) with pruritus, fever, and hepatitis. This patient's chronic scaly rash is not consistent with a hypersensitivity rash. (Choice D) Seborrheic dermatitis is characterized by erythematous, scaly plaques affecting the scalp, face, chest, and intertriginous areas. It can be associated with dementia (eg, Parkinson disease). However, the hands are not typically affected, and it does not cause gastrointestinal symptoms. (Choice E) Systemic lupus erythematosus causes a photosensitive rash in a malar distribution. CNS manifestations (eg, psychosis) can occur. Although isoniazid can cause drug-induced lupus (eg, positive antihistone antibodies), a rash is uncommon and would make this diagnosis less likely. With lupus, gastrointestinal involvement typically causes impaired motility, and diarrhea is not typical. In addition, this patient's diet makes pellagra more likely. (Choice F) Ulcerative colitis (UC) causes bloody diarrhea as opposed to the watery diarrhea seen with pellagra. Although UC can have extraintestinal manifestations, associated skin findings include erythema nodosum and pyoderma gangrenosum, not scaly dermatitis. Educational objective: Pellagra is due to niacin deficiency and is characterized by the "3 Ds": dermatitis, diarrhea, and dementia. Prolonged isoniazid therapy can interfere with niacin metabolism and occasionally cause pellagra.

A 42-Year-Old Man Who Recently Emigrated from Northern Africa Comes