The objective of this research is to collect data to create an observatory of microcrystalline rheumatism (gout and calcium-crystal rheumatism) in patients treated at the Groupement des Hôpitaux de l'Institut Catholique de Lille, in order to better understand the disease and improve patient care, in particular with the help of medical imaging.

All patients already included in another observational study set up in 2016 and meeting the eligibility criteria may be included in this study. An information letter will be sent to them by mail. If they wish to oppose to the use of their data, they can then return the objection form.

This sample will be supplemented by new patients who are recruited during a classic rheumatology consultation. The investigator will propose the study to all patients meeting the inclusion and non-inclusion criteria.

They will be informed of the objectives of the study and their rights. For patients who agree to participate in the study, sociodemographic and clinical characteristics will be collected.

Depending on the usual care, they will benefit from an ultrasound and/or a dual energy scanner (M0). Imaging data will be collected. Routine clinical follow-up is then carried out in consultation, with collection of clinical and biological evolution data, and morphological data if necessary if imaging is rechecked, until the patient is lost to follow-up or the follow-up is interrupted at the GHICL for any reason.

Available quarterly or semi-annual data will be collected.

Inclusion Criteria:

• Diagnosis of gout according to American College of Rheumatology /European League Against Rheumatism (ACR/EULAR) 2015 criteria OR diagnosis of calcium pyrophosphate dihydrate crystal deposition disease (CPPD) based on EULAR 2011 recommendations OR diagnosis of hydroxyapatite crystal rheumatism (HCR) according to a typical clinical sequence and demonstration of compatible calcium deposits on imaging
• patient who will benefit or has benefited from an ultrasound and/or DECT evaluation of microcrystalline deposits
• clinical suspicion of microcrystalline rheumatism requiring further imaging to confirm the diagnosis

Exclusion Criteria:

• Refusal or contra-indication to perform ultrasound or dual energy scanning.
• Patient's opposition to the use of his or her health data for research purposes
• Patient under guardianship or curatorship
• Pregnant woman
• Person not affiliated to a social security scheme or entitled to a social security benefit

Gout Chondrocalcinosis Hydroxyapatite