A 22-month-old boy born to non-consanguineous parents with pre-morbid normal development, presented with loss of previously acquired developmental milestones and recurrent head drops for the past 3 months. He was completely unimmunized and had a history of exanthematous febrile illness resembling measles at the age of 11 months. On examination, he was in a minimally conscious state, with generalized dystonia, intermittent choreoathetosis and repetitive myoclonic jerks.

Electroencephalography showed generalized periodic epileptiform discharges, with bursts comprising of high amplitude spike and slow-wave complexes. MRI brain showed patchy periventricular white matter signal changes. CSF measles specific IgG levels were elevated (1:625), confirming the diagnosis of subacute sclerosing panencephalitis (SSPE). He was started on isoprinosine and antiepileptic drugs. At 6 week follow up, myoclonic jerks had subsided; however, he was in vegetative state and had persistent extrapyramidal features.

The clinical course of SSPE was atypical, did not follow the classic four stages of the Jabbour Classification [1] and had history of pre-existing developmental delay or seizures. As compared to older children, course of the disease was fulminant with rapid progression to a vegetative state and fatal outcome [4]. Genetically determined immune dysfunction in the first 2 years of life preventing a successful cell-mediated immune clearance of measles virus has been implicated in this short latency and fulminant course [5]. Other putative genetic factors include genetic polymorphisms of Toll-like receptor 3, programmed cell death-1, MxA, interleukin-4, and interferon-1 genes [5]. Clinicians need to be aware of these important clinical observations to suspect atypical presentation of SSPE in young children. Although neuronal ceroid lipofuscinosis and other lysosomal storage diseases remain the most plausible clinical differentials for progressive myoclonic epilepsy with onset less than two years of age, SSPE should be considered in an unimmunized toddler who presents with cognitive decline, extrapyramidal signs and symptoms, myoclonus and a rapidly progressive fulminant course particularly in developing countries.

3. Saurabh K, Gupta R, Khare S, Sharma S. Atypical subacute sclerosing panencephalitis with short onset latency. Indian Pediatr. 2013;50:244-5.

4. Anlar B. Subacute sclerosing panencephalitis and chronic viral encephalitis. Handb Clin Neurol. 2013;112:1183-9.