To the Editor: Subacute sclerosing panencephalitis (SSPE) is a chronic progressive fatal encephalitis due to persistent measles virus infection [1] and is known to have varied clinical presentations leading to diagnostic delay and unnecessary work up [2]. We present an infantile onset SSPE, presenting as autoimmune encephalitis.

A 13-mo-old male child, presented with low-grade fever with coryza 40 d back for 3 d following which he was unable to sit/stand and hold neck. He was able to take feed during that time but was irritable. Later, he developed myoclonic jerks, followed by loss of social smile. On examination, anthropometry was within normal limits, with hypotonia, brisk reflexes, power >3/5, choreoathetosis and dystonia. MRI brain showed multiple non-specific subcortical white matter hyper-intensities and cortical hyper-intensities in T2 and T2 FLAIR. EEG showed diffuse slowing with high voltage spikes, sharp waves. Routine metabolic screening was normal. In view of subacute encephalopathy, seizures, choreoathetoid movements and MRI brain, the infant was treated as autoimmune encephalitis. CSF was normal and autoantibody panel was negative; CSF for oligoclonal bands were positive. Repeat EEG revealed periodic burst suppression pattern. Parents gave history that mother had a history of fever with rash at birth. There was no history of rashes and fever in baby. Baby received measles vaccination at 9 mo of age. CSF for measles IgG antibody was positive. Diagnosis of atypical SSPE with short latency was made and isoprinosine was added.

Zwiauer et al. reported a case of rapidly progressive SSPE after perinatal infection [3]. It is important to be aware of atypical fulminant presentations of SSPE, especially in developing countries where prevalence of measles is high and its myriad presentation. Starting empirical immunotherapy could precipitate rapid deterioration of SSPE. To conclude, SSPE can be present in infancy especially if mother is infected during the perinatal period even if the baby has been immunized for measles.