AJR 2004; 183:995-999
© American Roentgen Ray Society
Imaging Findings in Three Cases of the Nodular Type of Muscular Sarcoidosis
C. Tohme-Noun1,
C. Le Breton1,
A. Sobotka1,
Z. E. Boumenir1,
B. Milleron2,
M. F. Carette1 and
Antoine Khalil1
1 Department of Radiology, Hôpital Tenon, 4 Rue de la Chine, Paris 75970,
Cedex 20, France.
2 Department of Pneumology, Hôpital Tenon, Paris 75970, Cedex 20,
France.
Received July 7, 2003;
accepted after revision April 6, 2004.
Address correspondence to A. Khalil
(antoine_khalil{at}yahoo.fr).
Abstract
OBJECTIVE. Sarcoidosis is a granulomatous multisystem disorder that
may uncommonly involve muscle. We report the sonographic and MRI findings in
three cases of the nodular type of muscular sarcoidosis.
CONCLUSION. Intramuscular hypoechoic well-defined nodules in young
patients or patients with a history of sarcoidosis suggest the diagnosis of
intramuscular sarcoid. MRI is useful in detecting muscle sarcoid, evaluating
the extent and distribution of muscle involvement, and monitoring the patient
during follow-up after steroid therapy. MRI showed nodules that were iso- or
hyperintense relative to muscle on T1-weighted sequences. On T2-weighted
images and STIR sequences, we observed numerous intramuscular nodules of
homogeneous high signal intensity. All nodules enhanced homogeneously on
contrast-enhanced T1-weighted sequences. Disappearance of all nodules was seen
on follow-up sonograms and MR images after patients had received steroid
therapy.
Introduction
Sarcoidosis is a systemic granulomatous disease of unknown origin involving
many organs and tissues. It frequently affects the lung and hilar lymph nodes
[1]. Muscular involvement by
this disease is a rare condition. There are three main clinical types of
muscular sarcoidosis: the acute myositic type, the atrophic type, and the
nodular type. This entity has been recently described in the radiology
literature
[2–6].
In this study, we report three cases of the nodular type of muscular
sarcoidosis and describe the sonographic appearance and MRI
characteristics.
Materials and Methods
Our study included three men (ages: 28, 32, and 40 years; average age, 33
years) who had undergone sonographic and MRI studies of histologically proven
muscular sarcoidosis. All had pulmonary lesions of sarcoidosis on radiologic
examination. Sonography was performed with a 10MHz probe (Elegra, Siemens
Medical Solutions). The MRI studies were performed on a 1.5-T superconducting
magnet (Magneton Vision, Siemens Medical Solutions) using a body phased-array
coil. The MRI sequences included T1-weighted spin-echo images (TR/TE, 644/12),
fast spin-echo T2-weighted images (2,500/90), STIR sequences (4,176/29;
inversion time, 180 msec), and enhanced spin-echo T1-weighted images (IV
injection of 0.1 mmol/kg of gadoterate meglumine [Dotarem, Laboratoire
Guerbet]). Axial, coronal, and sagittal planes were used. Contrast-enhanced
sequences were obtained with and without fat saturation. The imaging matrix
was 256 x 256, and the section thickness was 7 mm with a 2-mm
intersection gap. A whole-body 67Ga (gallium citrate) scan was
obtained in two patients 24 hr after IV injection of 3.7 MBq/kg of body weight
of 67Ga. Anterior and posterior total-body images and spot images
at the lesion sites were obtained. No CT examination was done for muscular
lesion evaluation.
Results
In two of the three patients, symptoms related to muscle involvement
suggested sarcoidosis. The diagnosis was confirmed by transbronchial lung
biopsy and muscle biopsy that revealed noncaseating granulomas. In the
remaining patient, the diagnosis of disseminated sarcoidosis was made 3 years
before the diagnosis of muscular involvement. The clinical presentation was
asthenia (n = 2), painless swelling of both thighs (n = 3),
and erythema nodosum (n = 1). Physical examination showed muscle
weakness that was associated with palpable nodules (n = 2) in the
proximal parts of the lower extremities (n = 2) and in the distal
part (n = 1). Bilateral cervical and inguinal lymphadenopathy was
noted in one patient.
Chest CT revealed bilateral hilar and mediastinal lymphadenopathy in all
three patients and lung nodules in one.
Erythrocyte sedimentation rate (normal, 0–20 mm/hr) and creatinine
phosphokinase level (normal, < 130 IU/L) were elevated in all three
patients: 35–50 mm/hr (average, 40 mm/hr) and 280–344 IU/L
(average, 318 IU/L), respectively.
Doppler sonography was the first examination performed in the patient with
a prior diagnosis of sarcoidosis to rule out phlebitis because of the
appearance of lower limb edema. In the other two patients, sonography was
performed at the same time as MRI examination for investigation of palpable
nodules.
Sonography showed multiple intramuscular hypoechogenic nodules with clear
margins in all patients (Figs.
1A,
2A, and
3A). MRI revealed small (<
10 mm in diameter) increased-signal-intensity intramuscular nodular lesions on
STIR and T2-weighted images (Figs.
2B and
3B). Some of the nodules
appeared hyperintense relative to muscle on T1-weighted images
(Fig. 1B). Significant and
homogeneous enhancement was seen in each nodule (Figs.
1C,
2C,
2D, and
3C).
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Fig. 1A. —32-year-old man with nodular type of muscular sarcoidosis
involving both thighs. Longitudinal axial sonogram shows peripherally
well-defined tumorlike lesions of decreased echogenicity (arrows) in
muscle of left thigh.
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Fig. 3A. —40-year-old man with nodular type of muscular sarcoidosis
involving both thighs and legs. Longitudinal sonogram shows well-defined
nodules (arrows) of decreased echogenicity in left vastus lateralis
muscle.
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Fig. 2B. —28-year-old man with nodular type of muscular sarcoidosis
involving both thighs and legs. Muscular nodules (arrowheads) appear
of increased signal intensity and well defined on STIR image (TR/TE, 4,176/29;
inversion time, 180 msec).
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Fig. 3B. —40-year-old man with nodular type of muscular sarcoidosis
involving both thighs and legs. Axial STIR image (TR/TE, 4,176/29; inversion
time, 180 msec) shows nodular type of involvement in both thighs. Note
increased signal intensity of nodules (arrowheads).
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Fig. 1B. —32-year-old man with nodular type of muscular sarcoidosis
involving both thighs. Unenhanced axial T1-weighted MR image (TR/TE, 644/12)
clearly shows slightly increased-signal-intensity nodules
(arrows).
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Fig. 1C. —32-year-old man with nodular type of muscular sarcoidosis
involving both thighs. Contrast-enhanced axial T1-weighted MR image (644/12)
clearly shows multiple small nodules (arrows) in anterior muscles of
thigh. In each lesion, enhancement is intense and homogeneous.
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Fig. 2C. —28-year-old man with nodular type of muscular sarcoidosis
involving both thighs and legs. Contrast-enhanced axial T1-weighted MR image
(644/12) obtained with fat suppression shows multiple enhanced small nodular
lesions (arrowheads) in muscles of both thighs.
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Fig. 2D. —28-year-old man with nodular type of muscular sarcoidosis
involving both thighs and legs. Contrast-enhanced axial T1-weighted MR image
(644/12) obtained with fat suppression shows multiple intramuscular enhanced
nodules (arrowheads) in both lower legs.
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Fig. 3C. —40-year-old man with nodular type of muscular sarcoidosis
involving both thighs and legs. Contrast-enhanced axial T1-weighted MR image
obtained with fat suppression shows homogeneous enhancement of lesions
(arrowheads) of both thighs.
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Gallium-67 scintigraphy showed diffuse intake of radionuclide in muscles of
the right thigh, left leg, and both hands in one patient; there was no
accumulation of 67Ga in the muscles in the other patient.
All patients clinically improved after steroid treatment. MRI and muscle
sonography were performed on follow-up of two patients: one, 3 months after
the initiation of steroid therapy and the other, 5 months after. These studies
showed total disappearance of the muscular nodules.
Discussion
Muscular sarcoidosis is a rare entity, seen in approximately 6% of patients
with sarcoidosis [3,
7]. Muscular involvement is
usually asymptomatic [2,
5,
6] and occurs in 20–75%
of patients with sarcoidosis. Symptomatic muscle involvement is rare, noted in
less than 0.5% of patients with sarcoidosis
[1,
6,
8]. The reason why the presence
of granulomas is symptomatic in some patients and completely asymptomatic in
others is not known [9].
Muscles of the proximal portion of the extremities are frequent sites of
involvement [5].
There are three clinical types of muscular sarcoidosis
[1,
9]. The acute myositic type
occurs only in the early stage of sarcoidosis, in which the inflammatory
process may cause myalgia. MRI findings of this type are usually negative
because of the small size of the lesions
[4]. Patients with the chronic
myopathic type present with myalgia, weakness, and wasting of the muscles. MRI
findings reveal nonspecific muscle atrophy
[4]. Finally, the palpable
nodular type is the least common. This type is important to recognize because
it may be confused with a soft-tissue tumor.
In the current study, we described three cases of the nodular type. In the
first and second patients, muscle nodules were palpable, but in the third
patient, the main complaint was pain associated with edema and nonpalpable
nodules on clinical examination. In all patients, the proximal parts of the
lower extremities were involved and bilateral distribution was seen. Two
patients had simultaneous involvement of distal muscles. One patient was
treated for 3 years for sarcoidosis before developing symptomatic muscular
granulomas. Palpable muscular nodules revealed sarcoidosis in the two
remaining patients. In the nodular type, a solitary nodule or multiple nodules
within the skeletal muscles may be seen
[1], and these nodules are
typically oriented longitudinally. Radiologists must be aware in patients with
pulmonary sarcoidosis and painful leg muscles of the possibility of muscular
sarcoidosis or a differential diagnosis should be made with Doppler
sonography.
Otake et al. [3,
4] have described the MRI
characteristics of muscular sarcoidosis. The center of a sarcoid nodule shows
a star-shaped central structure of low signal ("dark star" sign)
on all axial pulse sequences and does not enhance after gadolinium
enhancement. The central portion of the nodule is found in the chronic stage
of muscular sarcoidosis, but not in the acute stage. According to those
authors, the fibrous tissue accounts for the decreased signal intensity of the
central element. The peripheral area shows slightly increased intensity on
T1-weighted sequences, significantly increased intensity on T2-weighted
sequences, and intense enhancement after injection. This is because of the
high cellularity of granulomas at this area and edema. On coronal and sagittal
images, Otake et al. described the "three stripes" appearance that
is not seen in other soft-tissue lesions.
Matsuo et al. [5] described
a similar appearance (i.e., a central star) on MRI of a woman who presented
with a mass in her lower leg that was proven to be a noncaseating granuloma at
biopsy. In the present report, none of the three cases showed a central
star-shaped structure. The nodules were of high homogeneous signal intensity
on T2-weighted images and STIR sequences and were iso- or hyperintense
relative to muscle on T1-weighted images. Nodule enhancement was homogeneous
and intense on contrast-enhanced T1-weighted images with fat saturation. No
surrounding edema or mass effect on adjacent muscles was detected in any of
our patients. All the nodules in our patients were small (< 10 mm in
diameter), and we think that the size of the lesion is an important feature in
identifying the central fibrous element. Some researchers suggest that the
central structure cannot be identified in small nodules because the period of
granulomatous inflammation is short for small nodules. However, on reviewing
the images of the different patients in the series of Otake et al.
[2–4]
and Matsuo et al., the central star was seen in nodules greater than 10 mm in
diameter, although the authors did not mention the dimension of the
nodules.
Sonography of muscular sarcoidosis has been described by few authors. Otake
[2] showed in his series a
central structure that is hyperechoic and a peripheral area that is hypoechoic
relative to the surrounding tissue. In our study, the nodules appeared
well-defined and hypoechoic and the central element was not identified because
of the small size of the nodules. In addition, sonography provided fairly good
tissue contrast because the nodules were usually in the superficial parts of
the muscles [2].
Gallium-67 scintigraphy is helpful in the assessment of active
extrapulmonary sarcoidosis. It is well known that 67Ga scintigraphy
shows uptake in sarcoid lesions of the lung and hilar lymphadenopathy, but
only a few reports about cases of muscular sarcoidosis have been published
[1,
2,
10–12].
Gallium uptake in the muscular parts of lower limbs and hands was seen in two
patients. In the third patient, no accumulation of radionuclide was identified
in the muscular parts, although these nodules showed enhancement on MRI. We
believe again that the lack of radionuclide uptake was due to the small size
of the sarcoid nodules.
Only one report in the literature
[3] has, to our knowledge,
described MRI features of muscle sarcoidosis after steroid therapy. According
to those authors, knowing whether the central star-shaped area persists after
treatment is important. All muscular nodules disappeared after corticosteroid
therapy. However, in these cases, a central structure was not detected before
therapy. Other studies must be done to confirm the characteristics of muscle
sarcoid after treatment.
In conclusion, muscular involvement by sarcoidosis should be considered in
the differential diagnosis of nodular muscular disease, especially in patients
with a history of sarcoidosis. The presence of characteristic bilateral
lymphadenopathy on chest radiography may help to establish the diagnosis. MRI
is useful in detecting muscle sarcoid, evaluating the extent and distribution
of muscle involvement, and monitoring the patient during follow-up after
steroid therapy. Sonography could be helpful in guiding percutaneous
biopsy.
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Abstract
Introduction
