Laboratory Studies
CBC count shows eosinophilia (10-40%) in as many as 80-90% of patients. In addition, pancytopenia, anemia, or thrombocytopenia may be encountered in eosinophilic fasciitis.
The erythrocyte sedimentation rate (ESR) is elevated in as many as 60-80% of eosinophilic fasciitis patients.
Immunoglobulin levels show hypergammaglobulinemia, usually polyclonal immunoglobulin G.
Muscle enzyme levels are sometimes elevated, especially aldolase.
The antinuclear antibody result is occasionally positive.
The rheumatoid factor result is occasionally positive.
A 2015 study showed elevated serum aldolase levels in 11 of 12 patients with eosinophilic fasciitis. Aldolase was more frequently abnormal than peripheral eosinophilia, hypergammaglobulinemia, and elevated ESR. They recommended serum aldolase be measured in all patients with suspected eosinophilic fasciitis and suggested aldolase values may play a role in disease monitoring. [22]
Imaging Studies
If clinically indicated, MRI of the involved areas shows a high-intensity signal in the fascia. A 2005 study demonstrated that MRI shows characteristic findings of fascial thickening, abnormal signal intensity, and contrast enhancement. According to the authors, these findings are useful to make the diagnosis, to guide the location for biopsy, and to monitor the response to therapy. [23]
Other Tests
If clinically indicated, electromyograms may show slow motor unit potentials with reduced duration and amplitude consistent with a myositis.
Pulmonary function test results may show a restrictive pattern with severe truncal involvement.
Procedures
If abnormal values other than eosinophilia are found on the CBC count, a bone marrow examination may be necessary.
A full-thickness incisional biopsy that includes the dermis, the subcutaneous fat, and the fascia is necessary to confirm a diagnosis of eosinophilic fasciitis.
Histologic Findings
The most profound changes associated with eosinophilic fasciitis occur in the superficial fascia, which is markedly thickened, fibrosed, and sclerotic. In the early stages, fibrinoid necrosis or myxoid degeneration may be seen. The fibrosis extends into the septae of the subcutaneous fat, which entrap the fat within intersecting bands of fibrosis. The fibrotic process also extends into the lower dermis and the underlying musculature. The muscle may show focal necrosis, degeneration, and regeneration.
The inflammatory infiltrate is usually mild to moderate and consists of lymphocytes, histiocytes, plasma cells, and variable numbers of eosinophils. Eosinophils are not required to make the diagnosis; the term eosinophilic fasciitis refers to peripheral eosinophilia not tissue eosinophilia. The inflammatory infiltrate, including lymphoid follicles, involves the lower dermis, the septae, the fascia, and the muscle. The epidermis, the papillary dermis, and the adnexa are usually spared. On direct immunofluorescence, immunoglobulin M is found at the dermal-epidermal junction, and immunoglobulin G and C3 are found around blood vessels in the lower dermis, the fascia, and the skeletal muscle.
Note the marked thickening and replacement of the entire dermis with sclerotic collagen on this incisional biopsy sample from the left posterior part of the thigh.
Photomicrograph of subcutaneous fat-fascia junction shows entrapment of subcutaneous fat by intersecting thick bands of fibrosis. Thickening and fibrosis of fascia and lymphoid aggregates are seen.
Photomicrograph of fascia-skeletal muscle junction shows markedly thickened fascia with heavy inflammatory infiltration.
High-power photomicrograph of fascia shows heavy inflammatory infiltration with numerous eosinophils, lymphocytes, and occasional plasma cells.
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Lower back part of the legs shows hypopigmentation, induration, biopsy site, and asymmetric involvement.
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Posterior thigh shows woody induration, sclerosis, and hypopigmentation.
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Close-up view of left posterior thigh 2 weeks later shows erythema, scaling, alopecia, and rippled induration.
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Posterior part of the calf in the first week of illness shows erythema, edema, alopecia, scaling, and early induration. The right calf is relatively uninvolved with patchy erythema only.
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Photograph of the posterior part of the calf at 3 weeks shows complete sclerosis and induration with patchy erythema.
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Note the marked thickening and replacement of the entire dermis with sclerotic collagen on this incisional biopsy sample from the left posterior part of the thigh.
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Photomicrograph of subcutaneous fat-fascia junction shows entrapment of subcutaneous fat by intersecting thick bands of fibrosis. Thickening and fibrosis of fascia and lymphoid aggregates are seen.
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Photomicrograph of fascia-skeletal muscle junction shows markedly thickened fascia with heavy inflammatory infiltration.
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High-power photomicrograph of fascia shows heavy inflammatory infiltration with numerous eosinophils, lymphocytes, and occasional plasma cells.
