AJR 2005; 184:S91-S93
© American Roentgen Ray Society
Thoracoabdominal Muscular Enlargement in Dermatomyositis: CT Visualization
Inna Postolov1,
Michael J. Rasiej2,
Dawn Hershman3,
Arthur P. Hays4 and
John H. M. Austin1
1 Department of Radiology, Columbia University Medical Center, New York,
NY.
2 Columbia University College of Physicians and Surgeons, New York, NY.
3 Department of Medicine, Columbia University Medical Center, New York,
NY.
4 Department of Pathology, Columbia University Medical Center, New York,
NY.
Received February 6, 2004;
accepted after revision May 11, 2004.
Address correspondence to I. Postolov, Department of Radiology, NYPH, 622 W
168th St., HP3, New York, NY 10032.
Introduction
Dermatomyositis is an immune-mediated myopathic disorder that
affects chiefly the proximal muscles of the extremities and, occasionally, the
torso. Like polymyositis, dermatomyositis is characterized by proximal muscle
weakness on physical examination and muscle edema on imaging studies
[1-6].
To our knowledge, CT visualization of thoracoabdominal muscular swelling in
dermatomyositis has not been previously described.
Case Report
A 62-year-old woman discovered a right breast mass. Biopsy showed a poorly
differentiated invasive ductal carcinoma positive for estrogen and
progesterone receptors and Her-2/neu overexpression. CT examination of the
chest and abdomen revealed enlarged right axillary and hilar lymph nodes,
multiple pulmonary nodules, and hepatic and splenic foci suspicious for
metastatic disease; thoracoabdominal muscles showed no abnormality. A
99mTc hydroxymethylene diphosphonate bone scan revealed no evidence
of metastatic disease.
After treatment with letrozole, a CT scan 4 months later showed a marked
decrease in the enlarged right axillary and hilar lymph nodes, and nearly
complete resolution of the pulmonary nodules. However, the patient developed
at that time symmetric upper extremity weakness and pain in the shoulder
regions. The symptoms progressed over a 2-month period to the proximal lower
extremities and included generalized fatigue. The patient also complained of
dyspnea and dysphagia. An esophagram showed marked hypopharyngeal pooling of
barium but no evidence for aspiration. Concurrently, the patient developed
facial swelling followed by whole-body edema, and a subtle, transient
erythematous discoloration of her face and upper chest manifested.
Discontinuation of letrozole did not result in clinical improvement.
Serum creatine kinase peaked at 887 U/L; erythrocyte sedimentation rate was
68 mm/h, C-reactive protein 61.8 mg/L, leukocyte count 7.0 x
109/L, serum albumin 2.2 g/dL, calcium 8.0 mg/dL, and magnesium 1.9
mg/dL. Antinuclear antibody titer was 1:160. No anti-DNA antibodies or
antiextractable DNA antigen antibodies were detected.
A follow-up CT examination of the chest to assess for possible metastatic
disease incidentally showed marked enlargement of the pectoralis major and
other muscles of the thoracoabdominal wall that were new since the CT
examination 2 months earlier (Figs.
1A,
1B,
1C,
1D and
1E). Because the CT findings
suggested possible active myositis, a right pectoralis major muscle biopsy was
performed. Light and electron microscopy showed the characteristic findings of
dermatomyositis (Fig. 1E).
Moderately large bilateral pleural effusions
(Fig. 1B) were presumed
secondary to hypoalbuminemia.
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Fig. 1A. —62-year-old woman with dermatomyositis and enlargement of
thoracoabdominal muscles. Midthoracic CT scan before onset of muscle disease
shows normal musculature of chest wall. Dermal thickening of right breast is
secondary to breast carcinoma.
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Fig. 1B. —62-year-old woman with dermatomyositis and enlargement of
thoracoabdominal muscles. Midthoracic CT scan 2 months after A and 2
months after onset of progressive muscular weakness and fatigue. Pectoralis
major muscles bilaterally and left pectoralis minor muscle are enlarged.
Pleural effusions are attributed to hypoalbuminemia.
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Fig. 1D. —62-year-old woman with dermatomyositis and enlargement of
thoracoabdominal muscles. Midthoracic CT scan at same time as B at T12
level shows marked enlargement of thoracoabdominal wall muscles, especially
laterally. Paraspinous muscles are not involved.
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Fig. 1E. —62-year-old woman with dermatomyositis and enlargement of
thoracoabdominal muscles. Photomicrograph (H and E stain; scale bar = 100
µm) of open biopsy of right pectoralis major shows muscle fibers with
atrophy and centrally located nuclei, and sparse lymphocytes in perimysium.
Abnormal fibers exhibit indistinct perifascicular pattern. Other areas of
muscle are nearly normal (not shown). Inset: Electron micrograph (scale bar =
1.0 µm) of swollen endothelial cell shows intracytoplasmic
microtubuloreticular aggregates (arrows), which are diagnostic of
dermatomyositis in appropriate clinical context.
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Prednisone and furosemide treatment and tamoxifen were started. Three
months later, the patient was switched to trastuzumab and docetaxel, and
prednisone was tapered because of gradual resolution of weakness and edema. A
follow-up CT examination 5 months later showed complete resolution of the
muscle enlargement and pleural effusions.
Discussion
Dermatomyositis is a rare, clinically and histopathologically distinct,
immune-related myopathic disorder, for which a severalfold increase in the
risk for cancers has been established
[1]. Clinical presentation
includes subacute to acute onset of proximal muscle weakness and a range of
erythematous skin changes. The classic dermatologic manifestations include a
heliotrope rash of the upper eyelids and Gottron's sign: bluish red plaques on
the backs of the knuckles [1].
Also seen are increased serum creatine kinase, dysphagia, and, in some cases,
interstitial lung disease [1,
6,
7]. Respiratory failure has
been reported as a result of rare involvement of the muscles of respiration
[7]. Pathogenesis of
dermatomyositis is characterized by changes in microvasculature, including
deposits of immune complexes in vessel walls and the presence of
microtubuloreticular structures in endothelial cells
[8]. Definitive diagnosis of
dermatomyositis requires a muscle biopsy to distinguish it from other
immune-related myopathic disorders, including polymyositis and inclusion body
myositis [1].
Because MRI is very sensitive for detecting even mild degrees of edema in
skeletal muscle [5], it has
been used for assessing proximal muscles of the limbs in inflammatory
myopathies [1,
2,
5]. Thoracoabdominal muscle
involvement occurs occasionally in dermatomyositis and has been shown using
99mTc methylene diphosphonate and thallium-201 chloride
scintigraphy [3].
Marked enlargement shown on CT of the pectoralis major muscles and the
abdominal wall muscles in the present patient led to an open biopsy of the
right pectoralis major muscle, establishing the diagnosis of dermatomyositis.
To our knowledge, CT visualization of an enlarged thoracoabdominal muscle
leading to a diagnostic biopsy has not been previously described in
dermatomyositis.
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Introduction
Case Report
