Gout and Pseudogout

A 62-year-old woman from Mumbai with a 10-year history of osteoarthritis of the knees presents with acute onset of severe pain, swelling, and warmth in both knees over 24 hours. She is afebrile. Synovial fluid aspiration from the right knee shows intracellular, positively birefringent, rhomboid-shaped crystals. The fluid is non-inflammatory (WBC 2,000/μL). Serum calcium is 9.2 mg/dL, phosphate is 3.8 mg/dL, and alkaline phosphatase is normal. What is the most likely diagnosis?

A 58-year-old man from Delhi presents with sudden onset of severe pain, swelling, and erythema of the right big toe joint that began 12 hours ago. He denies recent trauma. On examination, the first metatarsophalangeal joint is warm, tender, and swollen. He has a history of hypertension treated with hydrochlorothiazide and mild chronic kidney disease (creatinine 1.8 mg/dL). Synovial fluid analysis shows needle-shaped, negatively birefringent crystals under polarized light microscopy. Which of the following is the most appropriate immediate management?

Which crystal type is pathognomonic for acute pseudogout?