Beyond the Brain

Creutzfeldt-Jakob disease (CJD) is rare, but difficult to diagnose. At the moment, most conclusive diagnoses require either an invasive brain biopsy or a post-mortem examination – neither of which will be appealing for patients. To avoid causing patients unnecessary distress, a preliminary diagnosis is often made based on symptoms, such as cognitive decline, physical weakness and sensory and functional deficits. Unfortunately, none of these symptoms is exclusive to – or therefore fully diagnostic of – CJD.

Researchers at Case Western Reserve University School of Medicine saw the gap and wondered if the prions that cause the disease could be found in tissues other than the brain. To find out, they applied two laboratory assays – Western blotting and real-time quaking-induced conversion (RT-QuIC) – to skin samples taken from 23 CJD patients and 15 non-CJD controls (1). The first assay, Western blotting, was not sufficiently sensitive; it revealed prions in only two of seven CJD patients. RT-QuIC, however, detected prions in all 23 CJD patients and none of the control samples.

The results are a mixed bag, though. It’s great news for diagnosticians seeking an alternative to brain biopsy for their patients – but if infectious prions are present at detectable levels in the skin of CJD patients, then it raises concerns about potential transmission. The prions are notoriously tenacious – well known for their ability to stick to steel and survive many standard disinfection procedures. Is it possible that CJD could be transmitted, for instance via instruments previously used to perform surgery on an infected patient? Directly inoculating the brains of mice with CJD skin extracts did transmit the disease, but more research is required to discern whether or not standard hospital procedures involve the same risk.