Gout

Gout

Gout is the condition in which crystals of uric acids or urates are deposited in tissues.

Occurrence

Gout occurs in humans, birds and reptiles. In human, gout occurs in articular and periarticular tissues.

But in birds and reptiles, gout occurs in articular tissues, periarticular tissues, serous membranes of visceral organs and kidneys.

Types/ Forms of gout

1.      Articular gout

Articular and periarticular tissues are involved. Human beings, reptiles and birds are affected.

In articular gout, uric acid or urate crystals are deposited in articular and periarticular tissues and phagocytized by neutrophils and macrophages.

These cells release lysosomal enzymes and mediators of inflammation resulting acute inflammation in the joint.

Ultimately, foreign body reaction to the crystals (tophi) occurs at the site.

2. Visceral gout

Serous membranes of visceral organs and kidneys are involved.

Reptiles and birds are affected.

Gross appearance

1.      In articular form, whitish chalky nodules known as ‘tophi’ are found in the tissues.

In visceral form, the serous surfaces of visceral organs, especially the parietal surface of the pericardium, are covered by a thin layer of grayish granular materials that may have a metallic sheen.

Microscopic appearance

1.      Unstained acicular crystals of uric acids are found in affected area.

2.      Neutrophils, macrophages and foreign body giant cells are present.

Causes

Uric acids and urates are end products of purine metabolism.

In human-

1.      Hereditary tendency,

2.      Diet enriched with protein, calcium,

3.      Vitamin-A deficiency

     4. Renal diseases.

In birds and reptiles,

1.      Impaired renal function and clearance of urates,

2.      Nephrotoxic drugs,

3.      Dietary excess of protein and calcium,

4.      Vitamin-A deficiency and

5.      Dehydration.

Significance

1.      Visceral gouts in birds are only seen at necropsy.

2.      It is unknown whether birds or reptiles can recover from gout if the cause is removed.

3.      Articular gout is recurrent in human patients.