Calcinosis in Dermatomyositis

Calcinosis is a distressing late complication of juvenile DM [1, 2], but may appear early in the disease course [3] or be a consequence of externed therapy with corticosteroids [1, 4]. It may be expected in most long-term survivors of juvenile DM [1], but it occurs also in adults [5]. Calcinosis occurs in 30% [6] to 70% [7] of juvenile DM, and is two to three times more common than in adult DM [8]. In a large retrospective study was found cutaneous calcification in 20% of adults and 74% of children [9]. Approximately 25% of juvenile-onset classic DM patients have dystrophic calcification at the time of diagnosis, and 40–50% develop calcinosis sometime during the course of their disease [10]. Calcinosis is a late manifestation, with average duration of the disease in adults being 3.8 years prior to the clinical diagnosis. In both children and adults, the severity of calcinosis often correlates with the level of long-term disability [1]. It is usually a sign of “burned-out” myositis; it contributes to muscle atrophy and joint contractures [11]. Cutaneous calcinosis in DM usually appears between 4 months and 12 years after the onset of the disease, with an average time interval of 2–5 years between the disease onset and calcium deposition [8]. Calcium deposit in the skin is a common cause of cutaneous ulceration [11] and sterile necrotic abcesses [12].

Calcification associated with DM has been categorized into five different subtypes: (i) superficial calcifications present as small and hard plaques or nodules that can be felt just below the skin surface, (ii) subcutaneous calcifications—large tumorous deposits of calcium, which often appear “popcorn-like” on X-ray examination, (iii) intermuscular calcifications—deposits in the intermuscular fascia with limitation of movement in the involved muscle group, (iv) dystrophic calcification—a severe form, which resembles an exoskeleton, (v) a mixed form of calcinosis [1], and (vi) calcinosis universalis, which is loosely defined as numerous large deposits of calcium in the skin, subcutaneous tissue, muscles, and tendons [13]. Calcification of the muscles is generally asymptomatic, and may be seen only on radiological assesment [14]. Bone resorption markers, serum ionized Ca and urinary Ca levels point to the increased bone turnover and reduced excretion in patients with extensive calcinosis [15]. Complete regression of calcium deposits is not usually expected except in the first subtype [2].