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Joseph Junewick, MD FACR
over 6 years ago
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Juvenile Dermatomyositis

Case Detail

Anatomy: Musculoskeletal
Junewick
Joseph Junewick, MD FACR
Diagnostic Category: Infectious-Inflammatory
Created: about 1 year ago
Updated: about 1 year ago
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Modality/Study Types: DR
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History

Child with several month history of weakness, arthralgias and palpable abnormalities at the knee


Case Images


Diagnosis

Juvenile Dermatomyositis

Findings

DR – Numerous globular calcifications, predominantly in the subcutaneous soft tissues.

Discussion

Juvenile dermatomyositis (JDM) is a rare multisystem, autoimmune, inflammatory disease of the muscles and the skin. In the United States an average of 3.2 per 1 million children under 17 years old develop JDM. More females are affected by JDM than males (>2:1) and have two peak ages for developing JDM (6 and 11 years old) whereas males are more likely to develop JDM before 10 years of age. The exact etiology of JDM is unknown but it is thought to be secondary to an environmental trigger, such as infection, in genetically predisposed children leading to an autoimmune reaction. It is believed that both cell-mediated and humoral components of the adaptive immune system are responsible for the vascular and muscle damage characteristic of JDM. The diagnostic criteria include symmetric proximal muscle weakness, a heliotrope dermatitis and Gottron’s papules, elevated muscle enzymes, muscle denervation and myopathy by electromyography, and abnormal findings on muscle biopsy. Many patients with JDM experience arthralgias and arthritis early in the course of the disease commonly affecting, but not limited to, the knees.

Unique to JDM compared to its adult counterpart is the development of calcinosis cutis in up to 30-70% of patients within the first few years after disease onset. While the cause of calcium deposition in this disease is still under investigation, it is thought that autoantibodies directed against host endothelial cells lead to activation of the membrane attack complex and perifasicular muscle destruction by CD4+ T-cells resulting in the release of alkaline phosphate, from lysosomal tissue destruction, which causes organic phosphates to precipitate with calcium. Calcinosis often occurs at sites of the body prone to trauma, such as the elbows, knees, and buttocks, but does not ossify. There have been four recognized patterns of distribution in JDM with calcinosis occurring as 1) superficial firm, flesh colored nodules in the cutaneous or subcutaneous tissue 2) deep masses, 3) deep linear deposits within fascial planes, and 4) diffuse superficial deposits involving a majority of the body surface area. Patients at greater risk for soft tissue calcification include patients with untreated or poorly controlled disease for any reason, a polycyclic or unremitting disease course. The development of calcinosis often causes more morbidity for patients with JDM than the muscle involvement.

Not only can radiography identify areas and patterns of calcinosis early, which can help predict the disease course and prognosis, but it can also aid in establishing a diagnosis of JDM in the early phases by identifying muscle changes in the acute, inflammatory stage of the disease. MRI reveals edematous muscles, mostly of the arms, thighs, and chest wall, myositis, and elimination of the normal tissue planes indicative of early JDM. The amount of edema within the muscle tissue can help estimate the amount of inflammation and the findings on MRI can also help determine ideal muscle biopsy locations. The development of calcifications is associated with a chronic, continuous disease course. As such, the presence or absence and severity of calcinosis on the initial radiographic studies in a patient undergoing work-up for JDM hints at the disease duration prior to the diagnostic work-up. Computed tomography (CT) scans and ultrasound are useful in evaluating the presence or absence of calcification in patients and are very sensitive for identifying early calcifications and identifying the exact location of the calcinosis. 99m Tc MDP scintigraphy is the most sensitive study to evaluate the total amount of dystrophic calcification for these patients.

Reference

Batthish, M, Feldman, B. Juvenile Dermatomyositis. Current Rheumatology Reports. 2011;13:216–224. doi:10.1007/s11926-011-0167-9.

Sanyal, S. Radiographic Patterns of Soft Tissue Calcinosis in Juvenile Dermatomyositis and its Clinical Implications. Journal Of Clinical And Diagnostic Research. 2014;8(12):8–11. doi:10.7860/JCDR/2014/10787.5321.

Contributor

Brooke Boer, MS IV



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