BIOCHEMISTRY OF GOUT

1.1 Introduction

Gout was described by Hippocrates as “the disease of kings” due to its association with rich diet. (Falasca, 2006). Gout is a heterogeneous group of diseases resulting from the deposition of urate (as monosodium urate monohydrate) crystals in supersaturated extracellular fluids. It’s also a form of inflammatory arthritis characterized by recurrent attacks of a red, tender, hot, and swollen joint (Chen and Schumacher, 2008). Pain typically comes on rapidly in less than twelve hours (Richette and Bardin, 2010). The joint at the base of the big toe is affected in about half of cases (Schlesinger, 2010). It may also result in tophi, kidney stones, or urate nephropathy (Richette and Bardin, 2010).

Gout is due to persistently elevated levels of uric acid in the blood. This occurs due to a combination of diet and genetic factors (Richette and Bardin, 2010). At high levels, uric acid crystallizes and the crystals deposit in joints, tendons, and surrounding tissues, resulting in an attack of gout which may be first acute an then to chronic gouty arthritis. Nodular masses of monosodium urate crystals may be deposited in the soft tissues, resulting in chronic tophaceous gout. Gout occurs more commonly in those who regularly eat meat or seafood, drink beer, or are overweight (Beyl et al., 2016). Diagnosis of gout may be confirmed by the presence of crystals in the joint fluid or tophus. Blood uric acid levels may be normal during an attack (Richette and Bardin, 2010).

Gout affects about 1 to 2% of the Western population at some point in their lives. It has become more common in recent decades (Richette and Bardin, 2010). This is believed to be due to increasing risk factors in the population, such as metabolic syndrome, longer life expectancy, and changes in diet (Richette and Bardin, 2010). Older males are most commonly affected.

1.2 Signs and symptoms

Gout can present in multiple ways, although the most usual is a recurrent attack of acute inflammatory arthritis (a red, tender, hot, swollen joint) (Chen and Schumacher, 2008). The metatarsal-phalangeal joint at the base of the big toe is affected most often, accounting for half of cases (Schlesinger, 2010). Other joints, such as the heels, knees, wrists, and fingers, may also be affected (Schlesinger, 2010). Joint pain usually begins over 2–4 hours and during the night (Schlesinger, 2010). This is mainly due to lower body temperature (Eggebeen, 2007). Other symptoms which may rarely occur along with the joint pain include fatigue and a high fever (Eggebeen, 2007).Long-standing elevated uric acid levels (hyperuricemia) may result in other symptoms, including hard, painless deposits of uric acid crystals known as tophi. Extensive tophi may lead to chronic arthritis due to bone erosion (Terkeltaub, 2010). Elevated levels of uric acid may also lead to crystals precipitating in the kidneys, resulting in stone formation and subsequent urate nephropathy (Tausche et al., 2009).