Vitamin D, Parathyroid Hormone, and Acroosteolysis in Systemic Sclerosis

Objective. Sclerodactyly with acroosteolysis (AO) and calcinosis are prominent features of systemic sclerosis (SSc.), but the pathogenesis of these findings is poorly understood. Vitamin D and parathyroid hormone (PTH) have a crucial role in bone metabolism and resorption and may affect AO and calcinosis. We assessed vitamin D and PTH in patients with SSc. Methods. Medical records of 134 consecutive patients with SSc (American College of Rheumatology criteria) followed at the rheumatology department during the years 2003-2006 were reviewed for clinical assessment, laboratory evaluation [including 25(OH) vitamin D, calcium, phosphorus, alkaline phosphatase, PTH, creatinine, and albumin]; imaging data confirming AO and/or calcinosis. Patients followed routinely at least once a year were included (81 patients). Of these, 60 patients' medical records were found to have complete, relevant clinical, laboratory, and radiographic imaging. Results. Thirteen patients had diffuse disease and 47 limited disease - 51 women and 9 men, 44 Jews and 16 Arabs; mean age 55 +/- 14 years; disease duration 8 +/- 6 years. AO with or without calcinosis was observed in 42 patients (70%). Vitamin D deficiency was found in 46% of patients (16 out of 44 Jewish patients, 10 out of 16 Arab patients). PTH was elevated in 21.7% of patients. Significant correlations were observed between acroosteolysis and PTH (p = 0.015), calcinosis (p = 0.009), and disease duration (p = 0.008), and between PTH and vitamin D levels (p = 0.01). All patients had normal serum concentrations of calcium, phosphorus, magnesium, and albumin, and liver and kidney functions. Conclusion. In this group of Mediterranean patients with SSc, 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 vitamin 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 vitamin D deficiency in an Arab population but do not explain findings. The pathogenesis of these findings needs to be corroborated in other SSc population. (First Release Oct 1 2008; J Rheumatol 2008;35:2201-5; doi: 10.3899/jrheum.071171)