Background/Purpose: Calcinosis cutis is a debilitating complication of systemic sclerosis (SSc) affecting one quarter of patients. Repetitive trauma may be involved in the pathogenesis of calcinosis, and a prior single-center study found that the thumbs were most commonly affected, supporting this hypothesis. We sought to confirm this finding and to characterize the complications associated with calcinosis in a multi-center, international cohort of SSc patients.

Methods: We established a prospective cohort specifically to study calcinosis in SSc. We have to date enrolled 233 consecutive SSc patients who fulfill 2013 revised ACR/EULAR criteria at 9 centers within the United States, Canada, Australia, and Mexico. We performed a thorough physical exam of the entire body to assess for the presence of calcinosis, and collected detailed information on associated features. Calcinosis was defined as radiological or physical exam evidence of subcutaneous calcium deposition, or a clear history of extruded calcium.

Results: Our cohort was 88% female, and racial distribution was 64% Caucasian, 29% Hispanic, and 4% Asian. 55% had limited cutaneous disease. Mean disease duration from first non-Raynaud phenomenon (RP) symptom was 11.1 ± 9.3 years. Calcinosis was present in 90 patients (39%). Calcinosis developed 8.4 ± 9.0 years after first non-RP symptom. From 31 patients who had x-rays of the hands available, 21 (68%) had only radiographically detectable calcinotic lesions. The most common location of calcinosis was the hands (71%), followed by the elbows (19%), and the arms and/or forearms (16%). Within the hands, calcinosis most commonly affected the thumbs with decreasing frequency moving from the thumb to the little finger (50% thumbs, 37% index, 34% middle, 22% ring, and 18% in the little finger). Within patients with calcinosis of the hands, 25% had only right hand involvement, 11% had only left hand involvement, and 64% had bilateral hand involvement. 87% patients had multiple calcinotic lesions, and the median number of lesions was 2.5 per patient (range 1-13). 21% of patients had lesions >1 cm. The most common complications from calcinosis were tenderness (34%) and spontaneous extrusion of calcinosis through the skin (27%). Ulceration and infection were more rare (8% and 3% respectively). In patients with calcinotic lesions >1 cm, ulceration was more frequent (21% vs. 4%, p=0.015).

Conclusion: The majority of SSc patients with calcinosis presents with multiple, sub-centimeter lesions affecting the hands, most frequently in the right hand and in the thumb. Assuming that the dominant hand and the thumb are exposed to the most trauma, our study supports a role for trauma in the pathogenesis of calcinosis in SSc. Ulceration and infection are rare complications, but patients with larger lesions are more likely to suffer from ulceration of calcinosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comprehensive-characterization-of-calcinosis-in-a-multicenter-international-cohort-of-patients-with-systemic-sclerosis/