New research from the Spastic Paraplegia Centers of Excellence Research Network (SP-CERN). This summary is based on a paper published in the journal Annals of Clinical and Translational Neurology on January 5, 2026, titled "Diagnostic Utility of the ATG9A Ratio in AP-4–Associated Hereditary Spastic Paraplegia."

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Transcript:

New research from the Spastic Paraplegia Centers of Excellence Research Network (SP-CERN), a research group of the Rare Diseases Clinical Research Network.

Investigating the ATG9A Ratio as a Diagnostic Tool for Adaptor Protein Complex 4–Associated Hereditary Spastic Paraplegia.

This summary is based on a paper published in the journal Annals of Clinical and Translational Neurology on January 5, 2026.

Hereditary spastic paraplegia (HSP) is a group of inherited neurological disorders that cause the upper motor neurons to slowly degenerate, leading to progressive muscle stiffness and leg weakness. Adaptor protein complex 4–associated HSP (AP-4-HSP) is a childhood-onset and complex form of HSP that causes mislocalization—buildup in the wrong location—of the protein ATG9A. Gradual progression of initial symptoms, similarity with other developmental conditions like cerebral palsy, and unknown significance of genetic variants can make it challenging to diagnose AP-4-HSP.

In this study, researchers investigated the ATG9A ratio as a diagnostic tool for AP-4-HSP. The team measured the mislocalization of ATG9A in eight patients with suspected AP-4-HSP and genetic variants of unknown significance.

Results demonstrated loss of AP-4 function in six of the participants, revealing new disease-causing genetic variants. Authors note that the ATG9A ratio is a useful tool for diagnosing AP-4-HSP and classifying new genetic variants, which can help determine eligibility for clinical trials and guide treatment decisions.