AB0497 VITAMIN D, PARATHYROID HORMONE AND ACRO-OSTEOLYSIS IN SYSTEMIC SCLEROSIS

Y. Braun-Moscovici¹, D. Schapira¹, D. E. Furst², D. Markovits¹, A. Rozin¹, K. Toledano¹, P. J. Clements², M. A. Nahir¹, A. Balbir-Gurman¹
¹B.Shine Department of Rheumatology, Rambam Medical Center, Haifa, Israel, ²Rheumatology, University of California, Los Angeles, United States

Background: Sclerodactyly with acro-osteolysis (AO), and calcinosis are prominent features of Systemic sclerosis (SSc), but pathogenesis of these findings is poorly understood. Vitamin D and parathyroid hormone have a crucial role in bone metabolism and resorption and may affect AO and calcinosis.
Objectives: To assess vitamin D and parathyroid hormone (PTH) in SSc patients.
Methods: 56 Caucasian patients with SSc (13 diffuse and 43 limited disease; 8 males and 48 females, 42 Jews and 14 Arabs; mean age 55+/-14years [yrs]; disease duration 8+/- 6 yrs) underwent clinical assessment and laboratory evaluation including vitamin 25(OH)D (vit D), calcium (Ca), phosphor (Ph), alkaline phosphatase (AlPh), PTH, creatinine and albumin. AO and calcinosis were confirmed by X-rays.
Analysis: Spearman's correlation was utilized to find possible correlation between AO, calcinosis, PTH, Vit D, disease duration, age. Multiple Linear Regression was used to predict the value of one variable from another.

Results: Vitamin D deficiency was found in 46.4% of patients (16 out of 42 Jewish patients and in 10 out of 14 Arabian patients). PTH was elevated in 21.4% of patients. Significant correlations were observed between acro-osteolysis and PTH (r=0.341, P=0.01), calcinosis (r=0.396, P=0.002) , disease duration (r=0.387, P=0.003) and between PTH and vitamin D levels (r= -0.312, P=0.01). All patients had normal serum concentrations of Ca, Ph, AlPh,albumin and creatinine.

Conclusion: In this group of Mediterranean SSc patients, the incidence of vitamin D deficiency and secondary hyperparathyroidism was surprisingly high. This finding correlated with the occurrence of AO and calcinosis. Low levels of vit D may reflect silent malabsorption and might be a risk factor for secondary hyperparathyroidism and bone resorption. Traditional dress habits and low exposure to sun may contribute to vit D deficiency in an Arab population but does not explain all the findings.
The pathogenesis of these findings need to be corroborated in other SSc populations and efforts made to understand these interesting findings.