Abstract: The investigation of rare diseases is challenging because of the small number of patients and a frequently heterogeneous, multisymptomatic clinical presentation. Niemann-Pick type C (NPC), a progressive, neurodegenerative hereditary disorder, was long considered a pediatric disease. However, in the past decade, this view changed, given that a substantial number of adult NPC patients were diagnosed. Yet, we still know little about the clinical spectrum of adult NPC. This article sheds further light on this topic. For this purpose, we based the disease characteristics of the subpopulations of pediatric versus adolescent and adult NPC patients on the available literature as well as expert opinions regarding epidemiology, genetic mutation pattern, pathology including prodromal symptoms, progression rate, general treatment regime, and treatment effects. As outlined, NPC emerges as a disease continuum based on broadly similar genetic mutation patterns and pathophysiology across age groups. Pediatric and adolescent/adult patients are characterized by diverse facets of progressive neuropsychological manifestations, such as cognitive deficits and marked limitations in their motor abilities (including consideration of prodromal symptoms). NPC progresses similarly in pediatric and adolescent/adult patients, albeit with an accelerated rate of progression and thus a shortened life expectancy the younger the patients are when neurological symptoms first appear. However, the high disease burden of all NPC patients indicates the severity of this metabolic disorder. The treatment of NPC is interdisciplinary, regardless of age. To date, there is no causal therapy option. [ABSTRACT FROM AUTHOR]