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Milwaukee Shoulder — SCE Rheumatology MCQ

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HardCrystal ArthropathyMilwaukee ShoulderSCE Rheumatology

A 76-year-old woman has progressive shoulder swelling and loss of movement. She is afebrile and has no sensory deficit in the affected limb. Aspiration yields 180 mL of blood-stained fluid with 900 leucocytes/mm³; Gram stain and prolonged cultures are negative. No crystals are seen by compensated polarised-light microscopy, but the deposit is strongly positive with alizarin red S. Radiographs show rapid glenohumeral joint destruction, superior migration of the humeral head and multiple loose bodies. Ultrasonography demonstrates complete loss of the rotator cuff. What is the most likely diagnosis?

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Correct answer: A — Milwaukee shoulder basic calcium phosphate arthropathy

This is Milwaukee shoulder syndrome, a rapidly destructive basic calcium phosphate, predominantly hydroxyapatite, arthropathy classically affecting older women. The discriminating combination is a very large haemorrhagic but low-cellularity effusion, alizarin red positivity, complete rotator-cuff destruction and rapid glenohumeral collapse with superior humeral migration. Basic calcium phosphate aggregates are usually not identified by routine compensated polarised-light microscopy. A Charcot shoulder can be markedly destructive but requires an underlying sensory neuropathy and does not explain the crystal findings. Septic arthritis is less likely given the indolent course, low synovial leucocyte count and negative prolonged cultures. Haemophilic arthropathy requires recurrent bleeding, while primary osteoarthritis alone does not adequately account for the massive haemorrhagic effusion and characteristic cuff-associated destructive phenotype.

Reference: Nadarajah CV, Weichert I. Milwaukee shoulder syndrome. Case Reports in Rheumatology. 2014;2014:458708. https://pubmed.ncbi.nlm.nih.gov/24551470/