Gout and pseudogout are both types of arthritis caused by the deposition of crystals in the joints, but they differ fundamentally in the type of crystals involved, their causes, typical affected joints, symptoms, and treatment approaches.
**Gout** is caused by the accumulation of monosodium urate crystals, which form when there is too much uric acid in the blood. Uric acid is a waste product that normally dissolves in the blood and passes through the kidneys into the urine. However, when uric acid levels become elevated—due to factors like genetics, diet, alcohol consumption, obesity, or kidney problems—it can crystallize and deposit in joints, triggering intense inflammation. Gout most commonly affects men in their 40s and older, and the big toe joint is the classic site of attack, although it can affect other joints such as the knees, ankles, wrists, and elbows. The onset of gout is usually sudden and extremely painful, often waking people up at night with severe joint pain, redness, swelling, and warmth. The pain peaks within 12 to 24 hours and can last for days to weeks. Over time, repeated gout attacks can lead to chronic joint damage and the formation of tophi—lumps of urate crystals under the skin.
**Pseudogout**, on the other hand, is caused by the deposition of calcium pyrophosphate dihydrate (CPPD) crystals in the joint space. Unlike gout, pseudogout is not related to uric acid levels or diet. Instead, it is often linked to aging and other metabolic or endocrine disorders such as hyperparathyroidism, hypothyroidism, hemochromatosis, and Wilson disease. Pseudogout tends to affect both men and women equally, especially those over 60 or 85 years old. The crystals in pseudogout are rhomboid-shaped and deposit mainly in larger joints like the knees, wrists, ankles, and shoulders. The symptoms of pseudogout mimic those of gout, including sudden joint pain, swelling, warmth, and stiffness, but attacks can last from one day up to four weeks and are often self-limiting. Pseudogout can be triggered by joint trauma, surgery, or severe illness, which may cause excess pyrophosphate in the synovial fluid due to cellular injury or enzyme deficiencies.
The **key differences** between gout and pseudogout can be summarized as follows:
| Aspect | Gout | Pseudogout |
|————————-|———————————————-|———————————————|
| **Crystal type** | Monosodium urate crystals | Calcium pyrophosphate dihydrate (CPPD) crystals |
| **Cause** | Elevated uric acid levels (hyperuricemia) | Excess pyrophosphate, often age-related or metabolic disorders |
| **Typical joints affected** | Big toe (most common), knees, ankles, wrists | Knees, wrists, shoulders, ankles |
| **Age and sex prevalence** | More common in men, usually 40s and older | Affects men and women equally, mostly elderly |
| **Trigger factors** | Diet (high purine foods), alcohol, obesity, kidney issues | Trauma, surgery, illness, enzyme deficiency |
| **Crystal shape under microscope** | Needle-shaped, negatively birefringent crystals | Rhomboid-shaped, positively birefringent crystals |
| **Duration of attacks** | Hours to days, can last up to weeks | One day to four weeks, often self-limiting |
| **Relation to diet** | Strongly related; diet can trigger attacks | Not related to diet |
| **Treatment focus** | Lowering uric acid levels, anti-inflammatory drugs | Managing inflammation, addressing underlying metabolic issues |
Diagnosing these conditions often involves joint fluid analysis, where