Gout And Pseudogout: An Informative USMLE Guide

Introduction

Gout and pseudogout are two distinct types of crystal-induced arthropathies that often present with similar clinical symptoms. It is essential for medical professionals to understand the differences between these conditions to provide accurate diagnosis and appropriate management. This guide aims to provide a comprehensive overview of gout and pseudogout, including their pathophysiology, clinical presentation, diagnostic approach, and treatment options.

I. Gout

A. Pathophysiology

Gout is a type of inflammatory arthritis caused by the deposition of monosodium urate crystals in joints and soft tissues. It is primarily characterized by hyperuricemia, which leads to the formation of urate crystals.

B. Clinical Presentation

1. Acute Gouty Arthritis:

   • Sudden onset of severe joint pain, commonly affecting the first metatarsophalangeal joint (podagra).
   • Joint is swollen, red, warm, and tender.
   • Pain often worsens at night and may be accompanied by systemic symptoms like fever.

2. Intercritical Gout:

   • Asymptomatic periods between acute attacks.
   • Chronic deposition of urate crystals may lead to the development of tophi (visible deposits of urate crystals) in joints or soft tissues.

C. Diagnostic Approach

1. History and Physical Examination:

   • Typical presentation of acute monoarticular arthritis.
   • Risk factors include obesity, high-purine diet, alcohol consumption, diuretic use, and renal impairment.

2. Laboratory Findings:

   • Elevated serum uric acid levels (>6.8 mg/dL).
   • Presence of negatively birefringent needle-shaped crystals in joint fluid analysis confirms the diagnosis.

D. Treatment

1. Acute Gouty Arthritis:

   • Nonsteroidal anti-inflammatory drugs (NSAIDs) like indomethacin or naproxen are first-line therapy.
   • Colchicine can be used if NSAIDs are contraindicated or not tolerated.
   • In severe cases, intra-articular glucocorticoids or systemic glucocorticoids may be required.

2. Chronic Management:

   • Lifestyle modifications: weight loss, low-purine diet, reduced alcohol intake.
   • Urate-lowering therapy (ULT) with medications like allopurinol or febuxostat.
   • Prophylactic colchicine or low-dose NSAIDs may be considered during the initiation of ULT to prevent acute attacks.

II. Pseudogout

A. Pathophysiology

Pseudogout, also known as calcium pyrophosphate deposition disease (CPPD), is an inflammatory arthritis caused by calcium pyrophosphate dihydrate (CPPD) crystal deposition in joints and soft tissues.

B. Clinical Presentation

1. Acute Pseudogout:

   • Similar to gout, sudden onset of severe joint pain.
   • Frequently affects large joints such as the knee.
   • Joint is swollen, red, warm, and tender.

2. Chronic Pseudogout:

   • Tophi formation is uncommon.
   • Radiographic findings include chondrocalcinosis (calcification of cartilage) in affected joints.

C. Diagnostic Approach

1. History and Physical Examination:

   • Acute monoarticular or oligoarticular arthritis.
   • Risk factors include older age, joint trauma, and metabolic disorders (e.g., hemochromatosis, hyperparathyroidism).

2. Laboratory Findings:

   • CPPD crystals may be seen in joint fluid analysis, identified by weakly positively birefringent rhomboid-shaped crystals.

D. Treatment

1. Acute Pseudogout:

   • NSAIDs are first-line therapy.
   • Colchicine can be used if NSAIDs are contraindicated or not tolerated.
   • Intra-articular glucocorticoids or systemic glucocorticoids may be required for refractory cases.

2. Chronic Management:

   • Similar to gout, lifestyle modifications and ULT may be considered in recurrent or severe cases.

Conclusion

Gout and pseudogout share similarities in clinical presentation, but their pathophysiology and crystal types differ. A thorough understanding of the distinctive features of these conditions is crucial for accurate diagnosis and appropriate management. By following the diagnostic approach and treatment options outlined in this guide, medical professionals can effectively manage patients with gout and pseudogout.