Background: Rheumatic diseases are associated with reduced bone mineral density (BMD) as measured by Dual Energy x-ray absorptiometry (DXA). Mixed connective tissue disease (MCTD) is a rare connective tissue disease, and about 25% of all cases have a pediatric presentation. One study has implied that osteoporosis is common in postmenopausal women with MCTD [1], but data regarding BMD and osteopenia are lacking in younger patients with the disease.

Objectives: To assess the frequency of osteopenia in a cohort of juvenile mixed connective tissue disease (JMCTD) patients compared to a matched control group and to explore associations between lower BMD and disease related variables.

Methods: BMD was measured in a cohort of 52 JMCTD patients with mean age 28.2 years (SD 10.3) and mean disease duration 16.2 years (SD 10.3), and 52 controls matched for age and gender. Forty-four (85%) were female, and Z-score was estimated in the 35 patients and 35 controls over 20 years of age. Inclusion criteria were fulfilment of the Kasukawa- or the Alarcon-Segovia criteria and symptom debut before the age of 18 years.

Results: Osteopenia in at least one area of measurement defined as Z-score ≤ -1.0 was found in 23 (61%) of patients and 15 (43%) of controls over 20 years of age (p <0.01) (Table 1). The most common location of osteopenia was the distal radius (49% of patients and 23% of controls, p <0.01). Osteopenic values were found more often in patients than controls also in the lumbal columna L2-L4 (20% vs 9%, p <0.01), in the hip (32% vs 6%, p <0.01) and in the proximal radius (43% vs 17%, p <0.01). Osteoporotic values defined as Z-score ≤ -2.5 were found in four patients (11%) and one control. None had osteoporotic fractures.

We found significant correlations between lower BMD and a high number of joints with active arthritis at diagnosis (spearman -0.36, p 0.03 in proximal radius, -0.38, p 0.03 in distal radius, -0,36, p 0.03 in the hip). A high number of joints with active arthritis at examination was significantly associated with lower BMD in the proximal radius (spearman r -0.40, p 0.02) and L2-L4 (spearman r -0.37, p 0.03). Low age at diagnosis was associated with lower BMD in proximal radius (spearman r - 0.46, p <0.01). We could not identify significant correlations between number of months treated with glucocorticosteroids and BMD values, nor did we find associations between prednisolone dose at time of diagnosis, 6 months after diagnosis or one year after diagnosis and BMD values after mean 16.2 years. No significant correlations between different measurements of disease activity and BMD were observed (physician global disease activity score, systemic lupus erythematosus disease activity index, Rodnan skin score). In multiple linear regression analyses the BMD scores for proximal radius were used as dependent variable, as this was the area with the most consequent low values in patients. Age at examination, age at disease debut, gender, and number of joints with active arthritis at diagnosis and at examination were treated as independent variables. Active joints at diagnosis (B -0.01, p<0.01) and age (B 0.004, p 0.02) was associated with low BMD score at time of examination.

Conclusion: Osteopenia is common in JMCTD patients after long-term disease duration compared to matched controls. Lower BMD after long-term disease duration seems to be associated with a high number of joints with active arthritis.

REFERENCES: [1] Bodolay E et. Al, Osteoporosis in MCTD, Clin Rheum. 2003.

Acknowledgements: NIL.

Disclosure of Interests: None declared.