A total of six patients (5 male, 1 female) with a diagnosis of PPMS with disease onset before the age of 18 years were identified. 

Patients presented at a median age of 15.5 years (range: 11-17 years), with at least one-year history of progressive deterioration of their balance (n=2) or progressive worsening of lower limb function (n=4). Dissemination in space on first MRI was seen in all patients. CSF OCB were detected in 5/5 patients tested. 

At 2-years, all patients developed lower limb spasticity, three patients developed cognitive difficulties, three had visual problems and three had bladder involvement. Median EDSS was 5.5 (range: 4 to 7.5).

Three patients (50%) had relapses during the progressive clinical course, two with new onset visual symptoms and one with worsening leg weakness and urinary symptoms.

All patients showed new lesions on repeat MRI imaging. Contrast enhancement was present in 3/4 (75%) during the disease course. 

Presentation with progressive neurological symptoms and signs in young people should prompt evaluation for genetic causes such as leukodystrophies, hereditary spastic paraparesis and mitochondrial diseases given the rarity of primary progressive course in pediatric MS. In the absence of an alternative diagnosis, with new therapeutic options becoming available for PPMS, this diagnosis should then be considered.