Prepared by Alan N. Brown, MD and Richard M. Silver, MD of
the Department of Rheumatology, Medical University of South
Carolina, Charleston, SC.
A 10-year-old girl with a 7-year history of a chronic disease
presented with pain localized to the left upper extremity. She had
been engaged in a play session with her sibling and was being swung
by the arms when an audible "snapping" sound was noted, followed by
pain overlying the left bicep muscle.
Juvenile dermatomyositis with a fracture of soft-tissue
calcinosis in the left biceps muscle
A radiograph of the left upper extremity shows linear
intramuscular bands of calcification between the radius and the
ulna. A linear, sharp, transverse lucency through a large calcium
deposit in the biceps muscle is noted (Figure 1).
Juvenile dermatomyositis (JDM) is the most common idiopathic
inflammatory myopathy (IIM) seen in children, constituting 85% of
all cases of childhood IIM.
The diagnosis of JDM requires the pathognomonic cutaneous findings
of Gotton's papules or the heliotrope rash.
The presence of these rashes distinguishes JDM from juvenile
polymyositis. Evidence exists for a distinct immunologic
pathogenesis for each of these two groups of childhood IIM.
Extramuscular manifestations of JDM include photosensitive rashes,
arthritis, vasculitis, and involvement of the cardiac, pulmonary,
and gastrointestinal systems.
Calcinosis (soft-tissue calcification) is common in JDM and has
been reported to occur in 30% to 70% of children with the disease.
Risk factors for the development of calcinosis include delay from
the onset of symptoms to initiation of therapy, a progressive
disease course, trauma, and treatment with low doses of
X-ray diffraction studies and electron microscopy have shown these
soft-tissue calcification to be composed of hydroxyapatite.
Radiographic findings early in the course of JDM include muscle
enlargement and the loss of the interface between muscle and
subcutaneous fat. Muscle loss and joint contracture may follow.
Calcinosis is most often seen in the proximal extremities on
radiographic studies. Four distinct patterns of calcinosis have
been described: linear intramuscular calcifications following
fascial planes, deep nodular (tumoral), superficial nodular, and
superficial reticular calcifications. Ultrasonography has
demonstrated calcium-laden intramuscular fluid collections in some
MRI findings include increased signal intensity on T2-weighted
images of affected muscle, as well as perimuscular edema and
enhanced chemical-shift artifact. Increased signal intensity is
likewise seen in subcutaneous fat. Signal intensity of muscle
returns to normal after successful therapy.
This case represents a unique radiographic finding, ie, fracture
of soft-tissue calcinosis, a common clinical manifestation of JDM.
To our knowledge, a similar clinical scenario has not been reported
in the medical literature.