Hello Awesomites!
The question has helped me to learn the pyrimidine biosynthesis and urea cycle better. Felt like sharing it.
The question has helped me to learn the pyrimidine biosynthesis and urea cycle better. Felt like sharing it.
Let's get started.
OROTIC ACIDURIA= Excessive excretion of orotic acid
in urine.
Orotic aciduria is caused by defect in either UMP synthase
enzyme or Ornithine trancarbomylase (OTC) enzyme.
When UMP synthase is defective, orotic acid builds up and
the synthesis of nucleic acid is impaired, leading to deficient hematopoiesis
and growth. Orotic aciduria is associated with megaloblastic anemia due to
decreased pyrimidine synthesis. This megaloblastic anemia is refractory to
Vitamin B12, folic acid supplementation. This megaloblastic anemia present in
infants.
SYMPTOMS
Lethargy
Fatigue
Incessant crying due to orotic acid crystals in
ureter produces colicky pain
Growth retardation
SIGNS
Tachycardia and faint
murmur due to hyperdynamic circulation in anemia.
LABORATORY INVESTIGATION:
Urine analysis show orotic acid crystals.
Peripheral blood smear show hypochromic
megaloblastic anemia and hypersegmented neutrophils.
We can distinguish this increase in orotic acid secondary to
OTC deficiency from hereditary orotic aciduria by looking at blood ammonia
levels and the BUN (blood urea nitrogen).
HYPERAMMONAEMIA is present in OTC deficiency.
TREATMENT
Administration of uridine, which is converted to UMP, will
bypass the metabolic block and provide the body with a source of pyrimidine.
Uridine triacetate is a drug approved by FDA to be used in the treatment of
hereditary orotic aciduria.
Have a great day.
-Upasana Y. :)
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