Hartnup Disease
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Hartnup Disease

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Summary

Hartnup Disease is an autosomal recessive metabolic disorder characterized by a dysfunction in the neutral amino acid transporter. This defect causes decreased absorption of nonpolar amino acids, specifically tryptophan. Since tryptophan is important for the synthesis of Vitamin B3 (Niacin), patients with Hartnup disease will also present with signs and symptoms consistent with Niacin Deficiency), with pellagra-like symptoms. Since clinical findings are primarily due to niacin/tryptophan deficiency, niacin supplementation and/or a high-protein diet can be used to treat the disease.

Key Points

  • Hartnup Disease
    • Autosomal recessive inheritance
    • Deficiency of neutral amino acid (eg, tryptophan) transporters in proximal renal tubular cells and on enterocytes
      • Increased excretion of tryptophan in urine and decreased absorption from the gut → decreased tryptophan levelsdecreased conversion to niacin --> pellagra-like symptoms
    • Treat with high-protein diet and nicotinic acid (niacin)


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