OBSOLETE: CLN9 disease

CLN9 disease was a provisional designation within the neuronal ceroid lipofuscinoses (NCLs), a group of inherited neurodegenerative lysosomal storage disorders. This entity was originally described in a small number of patients who presented with clinical features resembling juvenile neuronal ceroid lipofuscinosis (CLN3 disease) but in whom mutations in known NCL genes could not be identified at the time. Affected individuals exhibited progressive visual loss, seizures, cognitive and motor decline, and behavioral changes, typically beginning in late childhood. The brain and retina were the primary organ systems affected, with progressive neuronal loss and accumulation of autofluorescent lipopigment (ceroid-lipofuscin) in cells. This designation is now considered OBSOLETE. Subsequent molecular studies identified that patients originally classified under CLN9 disease were found to harbor mutations in the CLN5 gene (or other known NCL genes), and the condition has been reclassified accordingly. The Orphanet entry (ORPHA:228357) reflects this obsolete status. As such, CLN9 disease is no longer recognized as a distinct genetic entity. Patients previously given this diagnosis should be re-evaluated under current NCL gene classifications. Treatment for NCL disorders remains largely supportive, focusing on seizure management, physical and occupational therapy, and palliative care, though enzyme replacement therapy and gene therapy approaches are under investigation for some NCL subtypes.

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