Hartnup Ds

ETIOLOGY:

• Inherited as an autosomal recessive trait. 
• Heterozygotes are normal. 
• Consanguinity is common. . 
• Causative gene, SLC6A19

SIGNS & SYMPTOMS:

• Hartnup disease manifests during infancy with variable clinical presentation: 
  • Failure to thrive, 
  • Photosensitivity, 
  • Intermittent ataxia, 
  • Nystagmus, and tremor.
• Increased amounts of amino acids in the urine.
• A rash develops on parts of the body exposed to the sun. 
• Mental retardation, short stature, headaches, unsteady gait, and collapsing or fainting are common. 
• Psychiatric problems (such as anxiety, rapid mood changes, delusions, and hallucinations) may also result

• Symptoms may be triggered by:
  • Sunlight, 
  • Fever, 
  • Drugs, or 
  • Emotional or physical stress. 
  • Poor nutrition  
  • Deficiency of niacinamide. 

 DIAGNOSIS:

• In Hartnup disease, urinary excretion of proline, hydroxyproline, and arginine remains unchanged, differentiating it from other causes of generalized aminoaciduria, such as Fanconi syndrome.
• With urine chromatography, increased levels of neutral amino acids (e.g., glutamine, valine, phenylalanine, leucine, asparagine, citrulline, isoleucine, threonine, alanine, serine, histidine, tyrosine, tryptophan) and indican are found in the urine.
• Increased urinary Indican can be tested by Obermayer test.

TREATMENT:

• High-protein diet 
• Physical and chemical protection from sunlight
• Patients also should avoid other aggravating factors, such as photosensitizing drugs, as much as possible.
• In patients with niacin deficiency and symptomatic disease, daily supplementation with nicotinic acid or nicotinamide
• Neurologic and psychiatric treatment is needed in patients with severe central nervous system involvement.