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Diagnosis and Discussion - Case 1136

Final Diagnosis

Subacute sclerosing panencephalitis

Discussion

Subacute sclerosing panencephalitis (SSPE) is a progressive subacute encephalitis that usually presents years after an initial infection by measles. SSPE was first described by Dawson in 1933-1934 and first associated with measles virus by Bouteille in 1965. The clinicopathologic features of SSPE overlap somewhat with a second form of subacute measles encephalitis, known as measles inclusion body encephalitis (MIBE). While MIBE has a relatively rapid onset following acute measles infection and tends to occur in immunocompromised patients, SSPE affects patients with intact immune systems years to decades after initial infection. Histologically, SSPE generally shows more lymphocytic inflammation than MIBE and fewer viral inclusions. The abundance of viral antigen in MIBE lends itself to immunohistochemical detection, but antigen, as well as inclusions, may not be detectable in longstanding SSPE. Thus, the combination of positive in-situ studies for viral RNA and negative immunohistochemistry for viral antigen, as well as the patient’s absence of known immunosuppression or recent measles infection, strongly supported a diagnosis of SSPE over MIBE.

Conclusion

SSPE is a rare complication of measles infection that can present with absence of immunohistochemically detectable measles antigen. Clinicopathologic correlation is helpful in distinguishing SSPE from MIBE.

References

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