Approach Considerations
Blood tests
Blood tests may show minor elevations of serum creatine kinase or aldolase. However, in many cases, these enzyme levels are normal. Now that the genes are known, sequencing or polymerase chain reaction (PCR) assay studies could be performed, but the specific genes are still not available as tests that can be ordered from a commercial laboratory. Physicians might consider referring suspected cases to genetic clinics that have affiliations with groups actively researching SJS so that genetic studies can be performed.
Imaging studies
Imaging studies are of little use. Spinal films reveal kyphosis. Radiographs can reveal other skeletal deformities but generally are not necessary for diagnosis.
Muscle biopsy
Muscle biopsy findings of patients with SJS are consistent with a myopathy.
Histologic findings
Minor, ultrastructural abnormalities have been described in SJS, but no specific electron microscope signature is known for the disorder. Light microscope findings are usually suggestive of a myopathy. Variations in muscle fiber size are common. As the individual ages and the disease becomes more advanced, fat and connective tissue may replace muscle fibers.
EMG and Nerve Conduction Studies
The symptoms of muscle stiffness and of difficulty relaxing the muscles may prompt EMG and nerve conduction studies in a patient. Typically, the nerve conduction findings are normal. [13]
The EMG needle study may show continuous discharges. These discharges frequently have the individual appearance of positive sharp waves or fibrillations, but they occur in runs of many discharges.
In some cases, the discharges have been described as myotonic, which suggests a waxing and waning character. In other cases, the discharges have not shown waxing or waning. In such cases, they would be considered complex, repetitive discharges.
