On crystal examination, which type of arthritis shows needle-shaped negative birefringent crystals?

The presence of needle-shaped negative birefringent crystals on crystal examination is characteristic of gout. This condition is caused by the deposition of monosodium urate crystals in the joints due to elevated uric acid levels. During polarized light microscopy, these needle-shaped crystals appear as negatively birefringent, meaning that they change color depending on the orientation of the light.

In gout, the clinical presentation is often acute and can involve severe pain, swelling, and erythema in affected joints, commonly the big toe (podagra). The identification of these specific crystals in synovial fluid is crucial for confirming a diagnosis of gout, differentiating it from other types of arthritis such as pseudogout, which features rhomboid-shaped positively birefringent crystals instead.

Understanding the distinct morphological characteristics and behavior of the crystals associated with various types of arthritis is essential for accurate diagnosis and appropriate management.