Medicine:Arakawa's syndrome II

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Arakawa's syndrome II
Other namesMethionine synthase deficiency, Tetrahydrofolate-methyltransferase deficiency syndrome, and N5-methylhomocysteine transferase deficiency.[1]

Arakawa's syndrome II[2] 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.


This disorder causes neurological problems, including intellectual disability, brain atrophy and ventricular dilation, myoclonus, hypotonia, and epilepsy. [citation needed]

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


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.[citation needed]




It is called "Arakawa syndrome 2" after Tsuneo Arakawa (1949–2003), a Japanese Physician.;[2][3] in this context, "Arakawa syndrome 1" refers to Glutamate formiminotransferase deficiency.


  1. Online Mendelian Inheritance in Man (OMIM) 156570
  2. 2.0 2.1 synd/235 at Who Named It?
  3. Arakawa T (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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