mercoledì 18 luglio 2007
Sjogren syndrome involving the parotid glands
Figure 1 and Figure 2: There are diffusely enlarged, heterogeneous parotid glands with invasion of the carotid space and punctate calcifications in the left parotid gland. Discrete areas of low attenuation likely represent areas of parenchymal destruction or contained saliva.
Diagnosis: Sjogren syndrome involving the parotid glands
Sjogren’s syndrome is a chronic, systemic exocrinopathy secondary to lymphocytic infiltration of the salivary and lacrimal glands. Sjogren’s is the second most common autoimmune disorder after rheumatoid arthritis. Sjogren’s affects patients between 50-70 years of age with a 90% to 95% female predominance. Sjogren’s is primarily characterized by dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) although patients may develop symptoms referable to multiple organ systems similar to systemic lupus erythematosus. Certain systemic manifestations are unique to Sjogren’s syndrome such as interstitial nephritis, hyperglobulinemic purpura, and an increased risk of lymphoma. On the opposite end are patients complaining of dry eyes and mouth with vague symptoms of fatigue, myalgia, and cognitive dysfunction which may be difficult to distinguish from fibromylagia or depression.
The diagnosis of Sjogren’s syndrome involves both subjective and objective criteria. Patient’s complain of inadequate tear production and decreased saliva production. Ocular signs of corneal damage are present on physical exam (Schirmer’s or Rose Bengal) with a slit lamp exam. Laboratory diagnosis of Sjogren’s syndrome involves detection of antibodies to the Sjogren A or B antigen, SS-A (Ro) and SS-B (La). Labial biopsy and additional test indicating impaired salivary gland function may also be performed.
There are primary and secondary forms of the Sjogren’s syndrome. Primary Sjogren’s syndrome generally consists of dry eyes and mouth due to salivary and lacrimal gland destruction via autoimmune activation of lymphocytes. Secondary Sjogren’s syndrome, usually due to rheumatoid arthritis, causes symptoms related to exocrinopathy and collagen vascular disease. These patients have high titers of the SS-A antibody. Other secondary causes of Sjogren’s syndrome include systemic lupus erythematosus or scleroderma.
The imaging appearance of the parotid glands in Sjogren’s syndrome is varied and depends on the stage of the disease. The parotid glands may appear normal in the early stages. Multiple small cysts in both parotids can be seen in the intermediate form of the disease. Late stage Sjogren’s syndrome of the parotids involves large cystic and solid masses. The cystic components represent areas of destroyed gland or collections of saliva while the solid masses represent lymphoid aggregates which actively destroy the gland. Contrast enhanced CT typically demonstrates bilateral parotid enlargement, heterogeneous enhancement of solid and mixed cystic lesions and punctate calcifications. MR sialography is the best imaging test if Sjogren’s syndrome is suspected because of its ability to accurately stage the severity of the disease.