The pathology in scleroderma is thought to be threefold: 1) tissue fibrosis, 2) small-vessel vasculopathy, and 3) autoimmune response producing autoantibodies. Initially, the tissue fibrosis begins with an edematous phase, which is the active inflammatory phase, associated with erythema, pruritus, and nonpitting edema. After several weeks, this stage gives way to the fibrotic stage, during which excess collagen is deposited in the skin. Lasting several months to years, this stage leaves patients with inflexible skin and loss of function of the affected limbs. Eventually, the patients will develop contractures and atrophy.2
The small blood vessels are also affected in scelroderma by increased collagen deposition. The intima of both small and medium vessels become thickened with collagen, and this eventually leads to the obliteration of the lumen. The blood vessels' dysfunction leads to Raynaud's phenomenon, which can often occur months to years before the onset of scleroderma, digital pitting, ulcerations, and tissue absorption. Telangiectasias are the result of capillary dysfunction and can be seen on the fingers/palms, face, and mucous membranes, especially in the CREST variant.2
Pulmonary involvement in scleroderma has the most significant morbidity. Fibrosing alveolitis leads to pulmonary fibrosis or a vasculopathy similar to the process in the skin, resulting over time in pulmonary hypertension.2 The prevalence of pulmonary fibrosis is between 25% to 90%, depending on the ethnic background of the patient. Most patients develop pulmonary fibrosis within the first 3 years of the disease, but only a subset will go on to develop progressive pulmonary fibrosis. It is difficult to predict which patients will develop progressive pulmonary fibrosis, but if the patient has normal pulmonary function tests at presentation, then that patient is unlikely to go on to develop severe pulmonary fibrosis.3 The majority of patients with the CREST variant have significant roentgenographic abnormalities along with some degree of respiratory dysfunction.4 The roentgenographic abnormalities that are seen in patients with pulmonary fibrosis with scleroderma include bibasilar pulmonary fibrosis.5 Figure 1 illustrates a typical appearance. The best way to evaluate for pulmonary fibrosis is with pulmonary function tests, chest X-ray, and/or high-resolution CT scan. Studies also show an association of gastroesophageal reflux disease (GERD) with pulmonary fibrosis.
Musculoskeletal involvement in scleroderma is virtually universal and may begin with a flulike syndrome with fatigue, arthralgia, and myalgia. Occasionally in the diffuse variant, tendon friction rubs can be detected because of fibrin deposition.2 Subcutaneous calcinosis, as part of the CREST variant or diffuse variant, is often seen on the extensor surfaces and in areas that tend to have a lot of friction and is seen in approximately 58% of scleroderma patients.6 Acroosteolysis, seen in up to 80% of scleroderma patients, occurs in both limited and diffuse cases, and is basically the absorption of the distal phalangeal tuft. The absorption can lead to decreased tuft pulp and decreased underlying bone.6 It is thought that this absorption occurs because of increased pressure from the surrounding sclerotic tissue.7 Absorption of the phalangeal tuft can occur in a way that causes narrowing of the bone, giving it the name "penciling."7 The combination of calcinosis and acro-osteolysis, as seen in Figure 2, is considered to be pathognomic for scleroderma.6
Nonmusculoskeletal manifestations of scleroderma are also important. Cardiac involvement can present as a symptomatic or asymptomatic pericardial effusion, arrythmia, congestive heart failure, and myocardial fibrosis. An echocardiogram and an electrocardiogram can be ordered to help further evaluate cardiac involvement.2 Patients with gastrointestinal involvement may present with difficulty chewing, dysphagia, esophageal strictures, GERD, delayed gastric emptying, and general dysmotility of the small and large bowel, leading to bloating/ abdominal distention and diarrhea/constipation. These problems can be further evaluated using endoscopy and barium swallows.2 The most common renal manifestation in scleroderma was hypertensive renal crisis, which is now well controlled in most patients with the use of angiotensin-converting enzyme inhibitors.2
Scleroderma is differentiated from the other rheumatologic diseases mentioned in the differential diagnosis by its characteristic soft tissue pathology, the presence of Raynaud's phenomenon, and gastrointestinal involvement.
Scleroderma with calcinosis. Appl Radiol.