Rare Diseases Are More Common Than Their Name May Imply

Caroline Just, MD, FRCPC, CSC-EEG

When I was a medical student on my pediatrics core rotation, there was a previously healthy young boy admitted with new-onset refractory status epilepticus. He had been tried on more than a handful of anti-seizure medicines and had been hospitalized for months.

I dutifully wrote my notes and presented to my seniors. In the earnest naïveté that only a medical student could have, I was shocked that no one knew what was wrong with my young patient. For my senior residents and attendings, this uncertainty was an accepted part of the job, an unavoidable reminder that “modern” medicine truly understands only a fraction of medical illnesses, and likely an even smaller portion of neurological disease.

I was fortunate to have some rare continuity with this patient ‒ I cared for him again a few months later, this time on a pediatric neurology elective, myself freshly matched to a residency in adult neurology. To my relief and fascination, an etiology had been found: NMDA receptor encephalitis. More tangibly, this had led to a successful change in treatment strategy and a clinical improvement for the young patient. I looked forward to a career of continued learning and a rapidly evolving toolkit with which to help my patients.

One in 10 Americans has a rare disease. Rare diseases are not unique to neurology, but due to the breadth of the nervous system and its complexity, the number of rare diseases of neurological origin is staggering, and it is growing daily as we identify more genes and antibodies to explain neurological presentations. When I entered my neurology training in 2014, just a decade ago, anti-myelin oligodendrocyte glycoprotein (anti-MOG) antibody disease didn’t exist. Ten years later, it’s an entity that is diagnosed daily.

Yet, so many diseases remain rare and undiagnosed.

What impact does this have on our patients? It means patients feel both the isolation of illness, and the isolation of feeling lonely in their disease. It means patients may never encounter another person who has the same illness, and frequently encounter clinicians who have never heard of their disease. It means they and their families are trying to navigate the health care system to find subspecialized care, which they may have to travel for, all while adjusting to illness.

How can we continue to recognize and treat rare neurological diseases? Firstly, by educating our trainees and colleagues to recognize existing rare diseases. If you see one, it’s easier to recognize it the next time. When designing curricula for medical education, we can consider emphasis on rare diseases with treatments, where recognition can be lifesaving, such as ataxia with vitamin E deficiency, Fabry’s disease and Pompe disease.

Next, take advantage of colleagues and networks to seek advice. A number of academic and large medical organizations have developed centers for rare or undiagnosed neurological disorders, to which patients can be referred for second opinions. Consider “rare case rounds”, where difficult cases are presented to a group of clinicians (including learners) to brainstorm next steps. Collaborate with medical genetics. Write case reports and collaborate with colleagues for case series.

Finally, we should support research of rare diseases within our scientific institutions and industry. There are more than 10,000 clinical trials for neurological disorders currently recruiting, according clinicaltrials.gov (accessed Feb. 12, 2024). These are exciting times – a recent example is in the 2023 FDA approval of omaveloxolone, the first drug that slows progression in Friedrich’s ataxia.

There is much to look forward to in the treatment of rare diseases: imagine if all metabolic disorders had enzyme replacement therapy, if all mitochondrial disorders had treatments to reduce oxidative stress, if we could check exactly which cytokines were harming a patient in real-time and put together a targeted molecular treatment for acute therapy. We have come far, but there is far to go.

Dr. Just is a staff neurologist, Center for General Neurology, Cleveland Clinic Neurological Institute, and program leader, Neuro-Obstetrics. She is also an assistant professor of neurology, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University.