DISORDERS OF NUCLEOTIDE METABOLISM
SUBMITTED BY:RAHMA SHAH
DATED:1ST September 2008
INTRODUCTION TO NUCLEOTIDES
Purines are key components of cellular energy systems (e.g., ATP, NAD), signaling (e.g., GTP, cAMP, cGMP), and, along with pyrimidines, RNA and DNA production. Purines and pyrimidines may be synthesized de novo or recycled by a salvage pathway from normal catabolism. The end product of complete catabolism of purines is uric acid; catabolism of pyrimidines produces citric acid cycle intermediates.
Disorders of Purine Salvage
Gout is a disease created by a buildup of uric acid.In this condition, monosodium urate or uric acid crystals are deposited on the articular cartilage joints, tendons and surrounding tissues due to elevated concentrations of uric acid in the bloodstream.This provokes an inflammatory reaction of these tissues.
Hyperuricemia is a common feature of gout, so its presence supports a diagnosis of gout. However, gout can occur without hyperuricemia. Hyperuricemia is defined as a plasma urate (uric acid) level greater than 420 μmol/L (7.0 mg/dL) in males, or 380 μmol/L in females. However, a high uric acid level does not necessarily mean a person will develop gout. Urate is within the normal range in up to two-thirds of cases. If gout is suspected, the serum urate test should be repeated once the attack has subsided. Other blood tests commonly performed are full blood count, electrolytes, renal function, thyroid function tests and erythrocyte sedimentation rate (ESR). This helps to exclude other causes of arthritis, most notably septic arthritis, and to investigate any underlying cause for the hyperuricaemia.
A definitive diagnosis of gout is from light microscopy of fluid aspirated from the joints (this test may be difficult to perform) to demonstrate intracellular monosodium urate crystals in synovial fluid polymorphonuclear leukocytes....