Arakawa's Syndrome II
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Arakawa's syndrome II is an
autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...
dominant
metabolic disorder A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients, such as proteins, fats, and carbohydrates. Metabolic disorders can happen when abnormal chemical reactions in the body alter t ...
that causes a deficiency of the enzyme tetrahydrofolate-methyltransferase; affected individuals cannot properly metabolize
methylcobalamin Methylcobalamin (mecobalamin, MeCbl, or MeB) is a cobalamin, a form of vitamin B. It differs from cyanocobalamin in that the cyano group at the cobalt is replaced with a methyl group. Methylcobalamin features an octahedral cobalt(III) centre and ...
, a type of Vitamin B12.


Presentation

This disorder causes
neurological Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain, the spinal c ...
problems, including
intellectual disability Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signif ...
, brain atrophy and ventricular dilation,
myoclonus Myoclonus is a brief, involuntary, irregular (lacking rhythm) twitching of a muscle or a group of muscles, different from clonus, which is rhythmic or regular. Myoclonus (myo "muscle", clonic "jerk") describes a medical sign and, generally, is ...
,
hypotonia Hypotonia is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases ...
, and
epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrica ...
. It is also associated with
growth retardation Delayed milestone, also called developmental delays, is used to describe the condition where a child does not reach one of these stages at the expected age. However, in most cases, a wide variety of ages can be considered normal, and not a cause fo ...
,
megaloblastic anemia Megaloblastic anemia is a type of macrocytic anemia. An anemia is a red blood cell defect that can lead to an undersupply of oxygen. Megaloblastic anemia results from inhibition of DNA synthesis during red blood cell production. When DNA synth ...
,
pectus excavatum Pectus excavatum is a structural deformity of the anterior thoracic wall in which the sternum and rib cage are shaped abnormally. This produces a caved-in or sunken appearance of the chest. It can either be present at birth or develop after pubert ...
, scoliosis,
vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteri ...
,
diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...
, and
hepatosplenomegaly Hepatosplenomegaly (commonly abbreviated HSM) is the simultaneous enlargement of both the liver (hepatomegaly) and the spleen (splenomegaly). Hepatosplenomegaly can occur as the result of acute viral hepatitis, infectious mononucleosis, and his ...
.


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.


Diagnosis


Management


Eponym

It is called "Arakawa syndrome 2" after Tsuneo Arakawa (1949–2003), a Japanese Physician.; in this context, "Arakawa syndrome 1" refers to
Glutamate formiminotransferase Glutamate formimidoyltransferase is a methyltransferase enzyme which uses tetrahydrofolate as part of histidine catabolism. It catalyses two reactions: * 5-formimidoyltetrahydrofolate + L- glutamate tetrahydrofolate + N-formimidoyl-L-glutama ...
deficiency.


References


External links

* {{RareDiseases, 8265, Arakawa's syndrome 2 Syndromes affecting blood Vitamin, coenzyme, and cofactor metabolism disorders Autosomal dominant disorders Syndromes affecting the nervous system Syndromes with intellectual disability