Pellagra-like skin rash-neurological manifestations syndrome

Pellagra-like skin rash-neurological manifestations syndrome, also known as Hartnup disease (or Hartnup disorder), is a rare inherited metabolic condition caused by defective transport of neutral amino acids in the small intestine and kidneys. The disease is caused by mutations in the SLC6A19 gene, which encodes a sodium-dependent neutral amino acid transporter. This defective transport leads to reduced intestinal absorption and increased urinary loss of tryptophan and other neutral amino acids. Since tryptophan is a precursor of niacin (vitamin B3), its deficiency results in clinical features resembling pellagra. The condition primarily affects the skin, nervous system, and gastrointestinal tract. Key clinical features include a photosensitive pellagra-like skin rash that appears on sun-exposed areas, intermittent cerebellar ataxia, psychiatric symptoms (including emotional instability, anxiety, and sometimes psychosis), and characteristic neutral aminoaciduria detectable on urine analysis. Symptoms are often episodic and may be triggered by poor nutrition, sunlight exposure, febrile illness, or physiological stress. Many individuals with the biochemical abnormality remain clinically asymptomatic throughout life. Treatment is generally supportive and effective. Oral nicotinamide (niacinamide) supplementation is the mainstay of therapy and can prevent or resolve both cutaneous and neurological manifestations. A high-protein diet is recommended to compensate for the amino acid malabsorption. Sun protection is advised to minimize photosensitive skin reactions. With appropriate management, the prognosis is generally excellent, and symptoms tend to improve with age. Early diagnosis through urine amino acid analysis allows timely intervention.

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