Dystrophic calcification in muscles of legs in calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia syndrome: Accurate evaluation of the extent with ^99mTc-methylene diphosphonate single photon emission computed tomography/computed tomography

A 35-year-old man with calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia (CREST) syndrome presented with dysphagia since 1-year; Raynaud's phenomenon since 2 years; swelling and pain in bilateral calf muscles since 3 years. On examination, bilateral calf muscles were swollen and hard in consistency. Also noted were diffuse telangiectasias and sclerodactyly. Anti-nuclear antibody level was 1:320 speckled pattern and creatine phosphokinase levels were elevated (400 IU/l; normal: 60–174 IU/l). Anti-centromere antibody levels were mildly elevated (20.01) where a value of ≤20 is considered negative. Serum calcium and phosphate levels were normal (9.7 and 3.4 mg/dl, respectively). A radiograph of bilateral legs revealed multiple discrete radiodensities arranged linearly along the bony axis of the leg; predominantly in the inferior half along the muscle fibers. The patient was referred for ^99mTc-methylene diphosphonate (MDP) bone scintigraphy (BS) to rule out other sites of involvement. BS revealed areas of increased uptake in left thigh and bilateral leg region [Figure 1a, anterior; Figure 1b, posterior view; arrows]. Single photon emission computed tomography/computed tomography (SPECT/CT) of the leg region was performed in the same setting and it revealed calcification in the subcutaneous region and muscles of legs with ^99mTc-MDP uptake [Figure c–f, arrows]. Dystrophic calcification is deposition of calcium salts in degenerated tissues in the presence of normal calcium and phosphorus levels in the body.[1] The most common site is heart muscle and valves.[2] A number of causes can give rise to calcification in the muscles of legs like dermatomyositis, polymyositis, diabetic myonecrosis, etc.[3] CREST syndrome, a limited form of scleroderma, is a multisystem connective tissue disorder.[4] Scleroderma myopathy is a heterogenous entity comprising of patients either with primary inflammatory or fibrotic features.[5] There is a female preponderance, and anti-centromere antibody may be negative. Furthermore, patients with internal organ involvement are more prone to develop myopathy.[6] Early recognition of muscle involvement may result in the initiation of time appropriate therapy and thereby improving prognosis. The findings on BS are sometimes difficult to interpret because of various forms of extraskeletal uptake. Addition of SPECT/CT as seen in the present case often helps in the exact localization of extra-osseous uptake.[7] Extra-osseous uptake of MDP can be seen in a number of conditions like metastatic pleural or pericardial effusion, hepatic metastases, metastases of osteosarcoma; primary tumors like neuroblastoma; metabolic causes of serum hypercalcemia like renal failure, sarcoidosis, amyloidosis, myositis ossificans, ischemia, cellulitis, necrosis etc.[8] Muscle involvement is a poor prognostic factor in systemic sclerosis.[9] Calcification in muscles in scleroderma demonstrated on CT has been reported.[10] In this case, BS along with SPECT/CT helped in correct localization of the sites of calcification.

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Figure 1 ^99mTc-methylene diphosphonate (^99mTc-MDP) bone scintigraphy revealed areas of increased uptake in left thigh and bilateral leg region (a, anterior; b, posterior view; arrows). Single photon emission computed tomography/computed tomography of the leg region revealed calcification in the subcutaneous region and muscles of legs with ^99mTc-MDP uptake (c-f, arrows)

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