Homocystinuria

Homocystinuria is an autosomal recessive metabolic disorder which results in the accumulation of homocysteine due to decreased activity of cystathionine beta-synthase. 

Features of homocystinuria include: 

• Myopia Ectopia lentis (=lens dislocation) 
• Low IQ 
• Marfanoid body habitus 
• Thromboembotic events 
• Osteoporosis 

Homocystinuria is also associated with malar flush and livedo reticularis. 

Diagnosis: 

• Elevated plasma homocystine and methionine 
• Elevated urinary homocystine 

Treatment: 

• Methionine/protein-restricted diet 
• Pyridoxine (vitamin B6; a cofactor for cystathionine beta-synthase ) 
• Two types of homocystinuria exist – one responds well to pyridoxine, the other doesn’t 
• Possibly B12/folate supplements – these encourage conversion of homocystine back to methionine. 

References:

Harvey Mudd, S. et al. The natural history of homocystinuria due to cystathionine beta synthase deficiency. Am J Hum Genet. 1985; 37(1): 1-31.

OMIM: Homocystinuria. Avaliable at http://omim.org/entry/236200?search=homocystinuria&highlight=homocystinuria 

Picker, J. and Levy, H. Homocystinuria caused by cysthathionine beta-synthase deficiency. In: Pagon RA, Bird TD, Dolan CR, Stephens K, editors. GeneReviews [Internet]. Seattle (WA): University of Washington, Seattle; 1993-.2004 Jan 15