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Gout

Overview

Gout is a joint disease characterized by intense joint pain, redness, and swelling, particularly in the big toes where crystal deposition causes small areas of swelling known as tophi. Gout is a painful inflammatory arthritis that affects many people. It is usually caused by an excess of uric acid in the body. Typically, it only affects one joint at a time (often the big toe joint), but ankles, heels, knees, wrists, fingers, and elbows can all be affected. There are periods when symptoms worsen, referred to as flares, and when there are no symptoms, referred to as remission. Gouty arthritis, a worsening form of arthritis, can develop due to repeated bouts of gout. Gout has no cure, although it can be effectively treated and managed with medications and self-management strategies.

Causes

Gout is caused by the deposition of salt crystals in the joint spaces. These include monosodium urate and calcium pyrophosphate crystals. Deposition of crystals is always due to elevated levels of uric acid in the body. Uric acid precipitates and forms these crystals deposited in different body areas, particularly in the joint spaces where they react with joint tissue and cause gout. Reasons for elevated uric acid levels could be primary or secondary.
Primary reasons are concerned with overproduction and under excretion of uric acid in the body. These include genetic disorders such as Lesch-Nyhan syndrome and Glucose-6-Phosphate (G6PD) deficiency.
A Secondary increase in uric acid levels could be due to alcohol, dietary influences, metabolic disorders, other illnesses, and drugs that cause hyperuricemia. These include hypertension, anemia, diabetes mellitus, renal insufficiency, elevated levels of cholesterol, etc.

Types

Crystal induced arthropathies (disease of joints due to crystals) are classified into two types:

  • Gout- due to deposition of monosodium urate crystals which is always due to increased uric acid levels in the body, as discussed in detail in the above section.
  • Pseudogout- due to deposition of calcium pyrophosphate crystals. The reason for pseudogout could be idiopathic or unknown or caused by other conditions such as hyperparathyroidism and hemochromatosis.
    Initial treatment and management for both types, however, remain the same.

Risk Factors And Epidemiology

The worldwide incidence of the disease varies depending upon eating habits, environmental and genetic factors.
It is more common in males than in females. This is because estrogens can have a mild effect of causing excretion of uric acid from the body. Its incidence increases in postmenopausal women.
Populations in which genetic predisposition for diseases like Lesh-Nyhan syndrome and G6PD deficiency are more prone to developing gout.

Signs And Symptoms

Following are the signs and symptoms of gout:

  • Inflammation, redness, hotness, and pain in the big toe are highly suggestive of gout.
  • Other than the big toe, pain in the ankles, wrist, knees can also be noted.
  • Involvement of single joints initially and as the disease progresses, multiple joints can be involved.
  • Crystal depositions are termed tophi in soft tissues (in ears, fingers, toes, etc.)
  • Tophi can also be deposited in the eyes in case of eye involvement, causing blurring of vision and other ocular symptoms.

Complications

Complications of gout include the following:

  • Severe degenerative arthritis
  • Secondary infections
  • Uric acid nephropathy
  • Renal stones
  • Spinal cord impingement
  • Fractures in joints with crystal deposition

Diagnosis

Following investigations aid in the diagnosis of gout:

  • Complete blood count with inflammatory markers and renal function tests
  • Synovial fluid aspiration and analysis
  • Serum uric acid levels. Uric acid levels alone are not a characteristic of gout in the absence of symptoms. Therefore, joint aspiration and synovial fluid analysis remain the most accurate diagnostic test for uric acid. Still, it has its limitations as it is invasive and can be extremely painful in already inflamed joints.
  • 24 hours uric acid excretion in urine
  • Plain radiographs of joints that show joint erosions
  • Ultrasonography of joint spaces to see crystal deposition
  • MRI and CT may also be used to visualize joints and joint spaces in-depth

Differential Diagnosis

Differential diagnoses of gout include:

  • Acute arthritis
  • Sarcoidosis
  • Acute amyloidosis
  • Reactive arthritis
  • Rheumatoid arthritis
  • Hyperparathyroidism
  • Septic arthritis
  • Renal osteodystrophy
  • Trauma
  • Bursitis

Treatment

The purpose of treatment against gout is to:

  • Manage acute attacks by providing pain relief
  • Prevent acute flares from happening by lowering the already existing deposits of uric acid in the body
  • Prevent tissue deposition of urate crystals

Medications

In the acute phase, the following painkillers are used:

  • Non-steroidal anti-inflammatory agents (NSAIDs)
  • Corticosteroids
  • Colchicine
  • Combination of the drugs mentioned above for effective management of pain

Long-term management of gout focuses on lowering uric acid levels in the body. Medications used for this purpose include:

  • Allopurinol
  • Febuxostat
  • Probenecid
    Other therapeutic agents that may be considered include:
  • Fenofibrate
  • Vitamin C

Prognosis

With proper compliance to treatment and dietary modifications, the prognosis for acute gout is excellent. In the case of chronic gout, long-term therapy may be indicated. With chronic gout, the risk factors for cardiovascular disease and stroke also increase.

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