What is Dejerine-Sottas syndrome?

Neuropathy is the name for a group of genetic conditions causing damage to your nerves that connect your brain and spinal cord to the rest of your body.¹ Dejerine-Sottas syndrome (DSS) is the most common inherited neuropathy. Also known as Charcot-Marie-Tooth disease or CMT, the condition presents in around 19 people per 100,000, making it a rare disease.² DSS ultimately affects your ability to move by causing your peripheral nerves to thicken and enlarge. Peripheral nerves connect your brain and spinal cord to the rest of your body, allowing for sensations such as touch. The thickening reduces their ability to send signals, causing muscle weakness and eventually loss of ability to walk.³ Fortunately, DSS is not thought to shorten your lifespan or affect brain function at all.

This article will discuss the natural progression of DSS over many years and how you can look out for it. Awareness is incredibly important in allowing you to receive the appropriate care. Patients should also be monitored to further study the effects and progression of the condition in the hopes of one day finding a treatment or cure.

What causes DSS?

DSS is a genetic condition, meaning it is passed on by your parents.³ There are multiple  faulty genes that may cause the condition, including MPZ, EGR2, PMP22 and PRX. It appears the malfunction of the causative genes result in a loss of myelin. This is a protective layer that forms around your nerves. The causative gene has only been identified in around 45% of patients, suggesting other, currently unidentified genes may be involved. It is thought to proportionally affect males and females.

DSS can be caused in both a dominant and recessive manner, with the dominant condition causing an earlier onset.² Everyone has two copies of each gene with one passed on from each parent. If in its dominant form, there will be a 50% chance of passing on the condition to your children.³ If both parents are carriers of the recessive form, possessing one gene each, the odds are changed. The risk of the child getting DSS would be 25%, but there would be a 50% chance of them being a carrier and 25% chance of them not inheriting either gene. If they do not inherit either gene, they would not be able to pass the condition on to their children.

Risk factors

As DSS is a genetic disease, your likelihood of developing the condition is increased if other members of your family are affected.⁴ There are other neuropathy conditions, such as diabetes, that can cause similar symptoms. These can heighten the symptoms of DSS. Chemotherapy drugs may also worsen the condition. 

Symptoms

The symptoms presented with DSS can vary from person to person, but they often begin suddenly by two years of age. They tend to spread throughout your body, beginning with your legs, and worsen over time. The symptoms include:

• Tingling, prickling or burning sensations³ 
• Muscle weakness in back of your leg, spreading to the front
• Delayed motor skills: can take longer to begin walking
• Weakened forearm muscles
• Respiratory inefficiency: cannot take in enough oxygen or expel enough carbon dioxide
• Mild vision deficiencies
• Loss of heat sensitivity
• Pain
• Absence of reflexes
• Abnormal curvature of spine: scoliosis or kyphosis
• Stiffened joints² 
• High foot arches⁴ 
• Hammer toes - curled toes
• Footdrop - difficulty lifting your feet at the ankle

Diagnosis

The main way in which DSS can be diagnosed is via observation of symptoms.³ A doctor will observe for:

• Muscle weakness¹ 
• Reduction in size of muscle
• Decreased tendon reflexes
• Sensory loss
• Bone, joint or muscle issue - e.g. abnormal curvature of your spine

There are four main test methods a doctor will use in a diagnosis:

• Nerve conduction studies - metal wires are placed on your skin to induce a small electric shock.⁵ This will stimulate your nerves and the speed of their response will be recorded.
• Electromyography - needles are inserted in your skin to record the electrical activity of your muscles⁵
• Genetic testing - examination of your DNA to identify the presence of known causative malfunctioning genes
• Nerve biopsy - A small section of peripheral nerve is removed from your ankle to look for loss of myelin.⁵ They are rarely used

Therapies

Currently, there are no cures for DSS. Treatment plans focus on improving quality of life by focusing on supporting patients and managing their symptoms.³ Treatment plans should stress the importance of maintaining as much mobility, flexibility and muscle strength as possible and the earlier it is begun, the higher the chance of maintaining quality of life.¹ It is worth noting that not all forms of medication can be taken with DSS and so you should consult your doctor before taking anything. There are a combination of healthcare professionals a patient can see to ensure effective treatment. These include:

• Neurologists
• Physiatrists
• Orthopedic surgeons
• Occupational therapists

Potential components of a treatment programme include:

• Shoes with good ankle support - stabilises joints when walking
• Wheelchairs
• Ankle/foot surgery
• Paracetamol and anti-inflammatory medicine - relieves muscle pain
• Tricyclic antidepressants, carbamazepine or gabapentin - used to relieve nerve pain

The future of DSS

The largest funder of research for the brain and nervous system, including that of DSS is the NINDS.¹ Research is focused on ways to better understand, diagnose and treat the condition. The main method of doing so is by identifying the genes and proteins involved in DSS and solving how they cause nerve damage and affect myelin production. There has also been research focused on testing nerve growth factors, which function to develop and maintain nerve cells. 

Summary 

DSS is a condition affecting your peripheral nervous system and can severely impact your mobility. It is a genetic condition and usually onsets by the time a patient is two years of age. It is important to recognise the early symptoms and seek medical attention to maintain quality of life as much as possible. There is currently no cure, but research is directed towards finding the causative agents and manipulating the mechanisms to produce treatments.

Frequently asked questions

Is DSS contagious?

No. DSS is not contagious and you cannot catch it or pass it on to anyone else.

Can I still have children with DSS?

Yes. You may still have children although as the condition may cause complications, it is important to discuss this with your doctor. 

Does DSS affect the brain?

No. Current research shows that DSS affects the nerve system connecting your brain and spinal cord, but does not have any impact on brain function.