Introduction: Chondrocalcinosis results from calcium pyrophosphate crystals deposition in the joints. We report an exceptional case of aseptic psoas abscess with a deposition of calcium pyrophosphate crystals.
Case report: A 92-year-old man presented to our department for an acute onset of inflammatory pain in the left hip. Computed tomography detected a coxofemoral arthritis and multiple intramuscular collections located in the iliopsoas muscle and the gluteus minimus. A sample of the fluid was obtained with a guided aspiration, and its analysis revealed an inflammatory liquid with no bacteria but numerous calcium pyrophosphate crystals. The final diagnosis was thus a muscular calcium pyrophosphate deposition pseudo-abscess, associated with a hip arthritis.
Conclusion: Hip chondrocalcinosis is unusual, and the association with intramuscular deposition of calcium pyrophosphate crystals seems extremely rare as we found only four other published cases. A microcrystalline arthritis could have spread from the coxofemoral joint through the iliopsoas bursa and into the muscle. However, the imaging aspect with an abscess and a predominant muscular injury might suggest a mechanism of crystal formation originating directly within the muscle. The outcome was always favourable even if some patients required surgery.
Keywords: Abcès; Abscess; Arthropathies à cristaux; Chondrocalcinose; Chondrocalcinosis; Crystal arthropathy; Hanche; Hip; Muscle iliopsoas; Psoas muscle.
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