Arakawa's syndrome II

Arakawa's syndrome II 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.

Characteristics
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.

Genetics


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.

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