Arakawa's syndrome II

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Arakawa's syndrome II
Classification and external resources
OMIM 156570
DiseasesDB 32787

Arakawa's syndrome II[1] is an autosomal dominant metabolic disorder that causes a deficiency of the enzyme tetrahydrofolate-methyltransferase; affected individuals cannot properly metabolize methylcobalamin, a type of Vitamin B12.

It is also called Methionine synthase deficiency, Tetrahydrofolate-methyltransferase deficiency syndrome, and N5-methylhomocysteine transferase deficiency.[2]


This disorder causes neurological problems, including mental retardation, brain atrophy and ventricular dilation, myoclonus, hypotonia, and epilepsy.

It is also associated with growth retardation, megaloblastic anemia, pectus excavatum, scoliosis, vomiting, diarrhea, and hepatosplenomegaly.


Arakawa's syndrome II has an autosomal dominant pattern of inheritance.

Arakawa's syndrome II is inherited in an autosomal dominant manner. This means the defective gene responsible for disorder is located on an autosome, and one copy of the defective gene is sufficient to cause the disorder when inherited from a parent who has the disorder.


It is called "Arakawa syndrome 2" after Tsuneo Arakawa;[1][3] in this context, "Arakawa syndrome 1" refers to Glutamate formiminotransferase deficiency.


  1. ^ a b synd/235 at Who Named It?
  2. ^ Online 'Mendelian Inheritance in Man' (OMIM) 156570
  3. ^ Arakawa T et al. (1967). "Megaloblastic anemia and mental retardation associated with hyperfolic-acidemia: probably due to N5 methanphetimite transferase deficiency". Tohoku J. Exp. Med. 93 (1): 1–22. doi:10.1620/tjem.93.1. PMID 5300832. 

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