A 10-year-old boy whose family recently immigrated to the United States is brought to the physician with ataxia, myoclonus, and visual problems. His parents say that he began acting strangely and having difficulty with school work several months ago. After the appropriate workup, a brain biopsy is obtained and an RNA virus containing hemagglutinin is cultured from the tissue sample. Which of the following is the most likely diagnosis?

Question

A 10-year-old boy whose family recently immigrated to the United States is brought to the physician with ataxia, myoclonus, and visual problems.  His parents say that he began acting strangely and having difficulty with school work several months ago.  After the appropriate workup, a brain biopsy is obtained and an RNA virus containing hemagglutinin is cultured from the tissue sample.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_39ce_868e_9249_cf9931addd0b_MD0001_00 Measles virus is an enveloped, single-stranded RNA virus that is a member of the paramyxovirus family. Its genome codes for several viral structural proteins, including membrane-bound hemagglutinin (mediates cell surface adhesion) and matrix protein (important for viral assembly). Subacute sclerosing panencephalitis (SSPE) is a rare complication of measles that occurs in children or young adults several years after the initial infection. It is thought to be caused by a form of measles virus with a mutated or absent matrix protein that prevents mature (enveloped) virion particles from forming. However, the virus continues to replicate intracellularly, leading to a persistent, nonproductive infection that evades eradication by the immune system. Accumulation of viral nucleocapsids within neurons and oligodendrocytes results in the formation of intranuclear inclusions and eventually leads to inflammation, demyelination, and gliosis in many cerebral areas. Patients with SSPE have high titers of measles antibodies in the serum and cerebrospinal fluid (detectable as oligoclonal bands). The disease causes various neurologic deficits and dementia, and is relentlessly progressive and fatal. (Choice A) Creutzfeldt-Jakob disease is a rare form of rapidly progressive dementia that is caused by prions (abnormally folded proteins). It usually occurs in older patients (sporadic form), although younger patients can be affected after consuming prion-infected meat products (acquired or variant form). Brain biopsy will show spongiform transformation of the cerebral cortex. (Choice B) Guillain-Barré syndrome is a postinfectious autoimmune demyelinating disorder of the peripheral nervous system. It most commonly presents as a symmetrical ascending weakness with absent reflexes following an infectious respiratory or diarrheal illness. (Choice C) Multiple sclerosis usually manifests in patients 20-30 years old. It is characterized by a variety of visual (eg, optic neuritis, internuclear ophthalmoplegia) and sensory deficits occurring in a relapsing/remitting pattern. Brain biopsy will show focal demyelinated plaques with relative axonal sparing. (Choice D) Progressive multifocal leukoencephalopathy is an infectious demyelinating disorder caused by JC virus, a double-stranded DNA virus in the polyomavirus family. JC virus manifests with progressive neurologic deficits in immunocompromised individuals (eg, lymphoma, leukemia, or HIV infection). (Choice E) Progressive supranuclear palsy is a form of parkinsonism resulting from neurodegeneration of the midbrain and frontal subcortical white matter. It presents with rapidly progressive gait dysfunction and falls, executive function loss, and vertical gaze palsy. Brain biopsy usually shows deposits of abnormally phosphorylated tau proteins. Educational objective: Subacute sclerosing panencephalitis is a rare complication of measles infection that occurs several years after apparent recovery from initial infection. Oligoclonal bands of measles virus antibodies are found in the cerebrospinal fluid of these patients. __________ References: Subacute sclerosing panencephalitis: clinical and demographic characteristics. (http://www.ncbi.nlm.nih.gov/pubmed/25149833) Evidence that the hypermutated M protein of a subacute sclerosing panencephalitis measles virus actively contributes to the chronic progressive CNS disease. (http://www.ncbi.nlm.nih.gov/pubmed/11878891)

A 10-Year-Old Boy Whose Family Recently Immigrated to the United