Synovial Biopsy in the Diagnosis of Crystal-Associated Arthropathies.

BACKGROUND/ OBJECTIVE: This study seeks to assess the utility of synovial biopsy in the diagnosis of crystal-associated arthropathies (CAAs) in a clinical setting. METHODS: In this retrospective study, we reviewed biopsy reports involving synovial tissue between 1988 and 2015. We then reviewed the records of patients where the biopsy was performed for a clinical suspicion of CAA-the clinical group-and calculated the frequency of a positive diagnosis. The t test, Mann-Whitney-Wilcoxon test, and Fisher test were used to compare clinical characteristics of patients with and without a tissue diagnosis of CAA. We also reviewed cases of unexpected detection of crystalline disease involving synovial tissue-the incidental group. RESULTS: Among 2786 biopsies involving the synovium, we identified 65 cases in the clinical group and 33 cases in the incidental group. In the clinical group, a relevant diagnosis was obtained from synovial tissue in 36.9%, and a CAA was diagnosed in 20%. Restricting analysis to clinical biopsies performed for a primary suspicion of CAA, a relevant diagnosis was obtained in 61.3%, and a CAA was diagnosed in 38.7%. The incidental group comprised 1.2% of all synovial biopsies and included 7 mass lesions. Basic calcium phosphate was not reported on any biopsy in the study period. CONCLUSIONS: Synovial biopsy is a diagnostic option when suspected CAA is resistant to conventional modes of diagnosis. Crystalline diseases should be considered in the differential diagnosis of musculoskeletal mass lesions mimicking neoplasms.

Prevalence and incidence of non-gout crystal arthropathy in southern Sweden.

OBJECTIVE: To estimate the prevalence and incidence of non-gout crystal arthropathy in relation to socioeconomic factors in southern Sweden. METHODS: All patients (age ≥ 18 years) with at least one visit to a physician with the diagnosis of interest in the Skåne region (population of 1.3 million) in 1998-2014 were identified. Non-gout crystal arthropathy (ICD-10 codes M11.0-M11.9) was subclassified in four different groups: calcium pyrophosphate crystal deposition related arthropathy (CPPD), unspecified non-gout arthropathies, chondrocalcinosis, and hydroxyapatite crystal deposition disease. The crude and age-adjusted point prevalence on December 31, 2014, and the cumulative incidence during 2014 were calculated for all non-gout crystal arthropathies, CPPD, and other unspecified non-gout arthropathies overall and in relation to occupation, income, and level of education. RESULTS: The crude 2014 point prevalence (95% CI) and 2014 cumulative incidence (95% CI) of all non-gout crystal arthropathies were 0.23% (0.23-0.24) and 21.5 (19-25) cases/100,000 persons. Mean age (range) among all prevalent cases in 2014 was 71 (20-102) years and 56% were males. The point prevalence and cumulative incidence of CPPD were 0.09% (0.08-0.09) and 8 (7-10)/100,000 persons, respectively. The corresponding data for unspecified non-gout crystal deposition disease was 0.16% (0.16-0.17) and 15.6 (13-18)/100,000 persons, respectively. The prevalence and incidence of CPPD and unspecified non-gout crystal arthropathies were slightly higher in men and increased with age irrespective of gender. Unspecified non-gout crystal arthropathy but not CPPD was less prevalent in persons with ≥ 15 years of education, whereas there were no clear associations with occupation and income. CONCLUSION: The prevalence of all diagnosed non-gout crystal arthropathies was 0.23%, thus considerably less prevalent than gout in southern Sweden. CPPD and other unspecified non-gout crystal arthropathies are the predominant diagnoses, increasing with age and in men. With the exception for unspecified non-gout crystal arthropathies being inversely correlated to a higher level of education, no convincing association with the socioeconomic factors was found.

Calcium crystal deposition diseases - beyond gout.

The most common types of calcium-containing crystals that are associated with joint and periarticular disorders are calcium pyrophosphate dihydrate (CPP) and basic calcium phosphate (BCP) crystals. Several diverse but difficult-to-treat acute and chronic arthropathies and other clinical syndromes are associated with the deposition of these crystals. Although the pathogenic mechanism of calcium crystal deposition is partially understood, much remains to be investigated, as no drug is available to prevent crystal deposition, permit crystal dissolution or specifically target the pathogenic effects that result in the clinical manifestations. In this Review, the main clinical manifestations of CPP and BCP crystal deposition are discussed, along with the biological effects of these crystals, current therapeutic approaches and future directions in therapy.

The Limitations of Gram-stain Microscopy of Synovial Fluid in Concomitant Septic and Crystal Arthritis.

BACKGROUND: Rapid diagnosis of septic arthritis from Gram-stain microscopy is limited by an inherent false-negative rate of 25-78%. The presence of concomitant crystal arthritis in 5% of cases represents a particular diagnostic challenge. OBJECTIVES: This study aims to investigate the effects that a concomitant crystal arthropathy has on the ability of Gram-stain microscopy of synovial fluid to diagnose a septic arthritis. METHODS: This is a 22-year retrospective cohort study. Inclusion criteria were a positive synovial fluid culture result with a positive clinical diagnosis of septic arthritis. Results were correlated with the presence or absence of urate and calcium pyrophosphate crystals, and Gram-stain result. During this time our collection and analysis methods remained unchanged. All samples were collected in Lithium Heparin containers. Chi-squared test with a p value < 0.05 was considered significant. RESULTS: 602 synovial fluid samples were included. 162 cases of concomitant crystal arthritis were identified (27%). Of these, 16 (10%) had an initial negative Gram-stain. Out of the 440 samples with no crystals detected, 18 (4%) had an initial negative Gram-stain microscopy result (p < 0.05). CONCLUSION: The incidence of concurrent septic and crystal arthritis may be higher than previously thought. Synovial fluid samples in concomitant septic and crystal arthritis are significantly less likely to have a positive Gram-stain at microscopy than in cases of an isolated septic arthritis. We would advise the clinician to maintain a high index of suspicion for septic arthritis in these patients.