Tryptophanuria

Tryptophanuria

Tryptophanuria is a congenital metabolic disorder of various etiologies, damage to the absorption of a-amino acids in the renal tubules (the ability to convert tryptophan to kynurenine and then to niacin is reduced) and intestines (unabsorbed tryptophan is destroyed by the intestinal flora with the formation of indole compounds that can color urine blue).

Options (all r)

    • Hartnap’s disease (*234500), the content of tryptophan in the blood is not increased; this aminoaciduria is characterized by a pellagra-like photosensitive skin rash and transient cerebellar ataxia
    • Tryptophanuria with dwarfism (*276100, p) is clinically similar to Hartnup’s disease, but tryptophan absorption in the intestine is not impaired (i.e., there is no increase in urinary excretion of tryptophan derivatives)
    • Hypertryptophanemia is familial (600627). Clinical picture: joint pain, developmental delay, visual impairment, ocular hypertelorism. Laboratory data: tryptophanuria, hypertriptophanemia.

Pathogenesis. Among the amino acids found in the urine, tryptophan derivatives predominate, which will be necessary for the synthesis of endogenous vitamin PP, so the clinical picture is characterized by signs of vitamin PP deficiency.

Clinical picture

    • Pellagra-like photosensitive skin rash
    • Emotional lability, possible encephalopathy, transient cerebellar ataxia
    • Urinary excretion of tryptophan derivatives formed in the intestine and giving it a blue color.

Treatment

    • Nicotinamide or nicotinic acid
    • A diet high in protein and low in tryptophan.

See also Hypovitaminosis PP

ICD

    • E72.0 Disorders of amino acid transport
    • E70.8 Others

aromatic amino acid metabolism disorders

MSH. Tryptophanuria (234500, 276100, 600627)

Notes

  • Hartnap – the name of the patient, whose parents were cousins
  • Blue diaper syndrome is similar to Hartnap’s disease, when the absorption of α-amino acids in the renal tubules is additionally impaired, which leads to tryptophanuria. Sometimes this includes familial hypercalcemia with nephrocalcinosis and indicanuria.

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