What is dystrophic calcification? What CTDs are associated with it?
When calcification occurs in cutaneous tissues, it is called calcinosis cutis and can be divided into four categories: dystrophic, metastatic (high calcium × phosphorous product >70–75), idiopathic (e.g., tumoral calcinosis), and iatrogenic. Dystrophic calcification is the most common type (95%) and is secondary to nonmetabolic diseases such as CTDs or due to deposition of calcium salts in the damaged tissue. Calcium is deposited either as numerous large masses (calcinosis universalis) or a few small, localized masses (calcinosis circumscripta). Dystrophic calcifications are most commonly associated with systemic sclerosis, dermatomyositis, SLE, pseudoxanthoma elasticum, panniculitis, and trauma. Tests for serum calcium and phosphorous should be normal. Medical therapy is poor. Small lesions may be improved with intralesional corticosteroids, low-dose (1 mg/day) warfarin, minocycline (50–100 mg/day), ceftriaxone (2 g/day IV for 20 days binds calcium salts), carbon dioxide laser, or surgical excision. Larger lesions may be improved by high-dose diltiazem (3 mg/kg per day), probenecid (1.5 g/day), IV bisphosphonates (zoledronic acid 4 mg IV every 3–4 months for a year inhibits calcium apposition onto hydroxyapatite), topical sodium thiosulfate 25%, or surgical excision.