What are the new diseases emerging in neurology?

Medical futurists predict that scientific advances will lead to more precise definition of diseases. This will inevitably result in the emergence of more diseases and fewer syndromes. This case is made very eloquently in the book, The Innovators Prescription. Many neurological disorders currently wallow at the intuitive end of medical practice, and their journey towards precision medicine is painfully too slow. Neurology therefore has a great potential for the emergence of new disorders.

In the ‘good old days’, many diseases were discovered by individual observers working alone, and the diseases were named after them. In this way, famous diseases were named after people such as James Parkinson, Alois Alzheimer, and George Huntington. For diseases discovered by two or three people, it didn’t take a great stretch of the imagination to come up with double-barrelled names such as Guillain-Barre syndrome (GBS) or Lambert-Eaton myasthenic syndrome (LEMS).

Today, however, new diseases emerge as a result of advances made by large collaborations, working across continents. These new diseases are named after the pathological appearance or metabolic pathways involved (as it will require an act of genius to create eponymous syndromes to cater for all the scientists and clinicians involved in these multi-centre trials). This is unfortunately why new disorders now have very complex names and acronyms. Take, for examples, chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) and chronic relapsing inflammatory optic neuropathy (CRION). It is a sign that we should expect new neurological diseases to be baptised with more descriptive, but tongue-twisting, names.

 

New disease categories emerge in different ways. One is the emergence of a new disorder from scratch, with no antecedents whatsoever. Such was the case with autoimmune encephalitis, a category which has come from relative obscurity to occupy the centre stage of eminently treatable diseases. I have posted on this previously as What’s evolving at the cutting edge of autoimmune neurology and What are the dreadful autoimmune disorders that plague neurology? Other disease categories form when different diseases merge into a completely new disease category, or when a previously minor diseases mature and stand on their own feet. These are the stuff of my top 8 emerging neurological disorders.

 

1. mTORopathy

This huge monster is ‘threatening’ to bring together, under one roof, diverse disorders such as tuberous sclerosis complex, epilepsy, autism, traumatic brain injury, brain tumours, and dementia. You may explore this further in my previous blog post titled mTORopathy: an emerging buzzword for neurology.

2. IgG4-related autoimmune diseases

This new group of neurological diseases is threatening to disrupt the easy distinction between several neurological disorders such as myasthenia gravis (MG), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and Guillain Barre syndrome (GBS). It even includes the newly described IgLON 5 antibody disorder, something I blogged about as IgLON5: a new antibody disorder for neurologists. You may explore IgG4-related disorders in this paper titled The expanding field of IgG4-mediated neurological autoimmune disorders. 

3. Anti-MOG antibody disorders

Now, neurologists have always known about MOG, mostly as a minor bit player, an extra, so to say. No more, it is now all grown up and matured. And the growth is fast and involves many inflammatory demyelinating disease of the CNS such as fulminant demyelinating encephalomyelitis and multiphasic disseminated encephalomyelitis. How far will it go?

4. Hepatitis E virus related neurological disorders

A field which is spurning new neurological disorders is neurological infections, and Hepatitis E virus (HEV) is in the forefront. We are now increasingly recognising diverse Hepatitis E related neurological disorders. HEV has now been linked to diseases such as Guillain Barre syndrome (GBS) and brachial neuritis. And the foremost researcher in this area is Harry Dalton, a hepatologist working from Cornwall, not far from me! And Harry will be presenting at the next WESAN conference in Exeter in November 2017.

5. Zika virus

Zika virus is another novel infection with prominent neurological manifestations. We are learning more about it every day, and you may check my previous blog post on this, titled 20 things we now know for certain about the Zika virus.

6. Multisystem proteinopathy

Multisystem proteinopathy is a genetic disorder which affects muscles and bone, in addition to the nervous system. It is associated with Paget’s disease of the bone and inclusion body myositis, with implications for motor neurone disease (MND) and frontotemporal dementia (FTD). Quite a hydra-headed monster it seems, all quite complex, and perhaps one strictly for the experts.

7. GLUT-1 deficiency syndromes

GLUT-1 stands for glucose transporter type 1. Deficiency of GLUT-1 results in impaired transportation of glucose into the brain. GLUT-1 deficiency syndrome presents with a variety of neurological features such as dystonia, epilepsy, ataxia, chorea, and a host of epilepsy types. It starts in infancy and is characterised by a low level of glucose and lactic acid in the cerebrospinal fluid. Expect to hear more on this in the near future.

8. Progressive Solitary Sclerosis

And this is my favourite paradigm shifter. Neurologists often see people with brain inflammatory lesions and struggle to decide if they fulfil the criteria for multiple sclerosis (MS). The current threshold for concern is when there have been two clinical events consistent with inflammation of the nervous system, or their MRI scan shows involvement of at least two different sites of the nervous system. Well, dot counting may soon be over, going by this paper in Neurology titled Progressive solitary sclerosis: gradual motor impairment from a single CNS demyelinating lesion. The authors identified 30 people with progressive clinical impairment arising from a single inflammatory nervous system lesion. The authors were convinced enough to recommend the inclusion of this new entity, progressive solitary sclerosis, in future classifications of inflammatory disorders of the central nervous system. Move over progressive MS, here comes progressive SS. Neurologists will surely have their job cut out for them.

Do you have any suggestions of emerging neurological disorders? Please leave a comment

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PS. These disorders are all covered in neurochecklists