Introduction

Chanarin-Dorfman Syndrome (CDS) is a rare genetic syndrome that affects various aspects of an individual's life. It has been recognised for its involvement in the skin, liver, and particularly the muscles. Most individuals with CDS experience weakness of the muscles that can restrict daily functioning, impact independence, and decrease self-esteem. Although there is currently no cure for the condition, supportive therapies and rehabilitation can go a long way in enabling individuals to cope with the symptoms and lead a more active life.¹

Here, we will guide you through why muscle weakness occurs in CDS, what support therapies are out there, and how teamwork can make all the difference. We conclude with a glance at where the research is going and what may lie ahead for individuals with CDS.

Understanding Chanarin-Dorfman Syndrome: genetic and molecular causes

CDS, also referred to as neutral lipid storage disease with ichthyosis (INLSD), is a genetic disease transmitted in an autosomal recessive mode. In other words, both parents need to have one copy of the altered gene for their offspring to develop symptoms. The principal genetic offender for CDS is a mutation in the ABHD5 (also referred to as CGI-58) gene on chromosome 3p21. This gene codes for the protein adipose triglyceride lipase (ATGL) required for the breakdown of triglycerides, a vital type of fat stored in our bodies.^1,2,3

When the ABHD5 gene is defective, the body cannot turn the ATGL enzyme on. Without this enzyme functioning, triglycerides accumulate in tissues throughout the body, particularly in the muscles, liver, and skin. Eventually, this build-up manifests as symptoms like thickened, scaly skin, fatty liver, and weak muscles. The accumulation in muscles is especially relevant here: it makes the fibres that make it up lose their usual function and strength.^1,2,3

In short, the underlying problem is that the fat-burning machinery within the cell is impaired. This results in fat "droplets" filling up muscle cells, which can no longer contract as well and are generally weaker. The genetic error in ABHD5 initiates a chain reaction of alterations that affect muscles, nerves, skin, and even other organs.^1,2,3

Epidemiology and clinical presentation of muscle weakness in CDS

CDS is extremely rare, with more than 150 cases documented in medical literature globally as of recent reports. It most frequently affects individuals of Mediterranean, Middle Eastern, and certain South Asian descent, where populations may have elevated rates of marriages within the extended family, furthering the chances of those unusual genetic pairings.⁴

The clinical presentation is varied. In early life, the majority of patients are characterised by their dry, scaly skin (ichthyosis) at or soon after birth. In childhood, additional problems arise, such as:⁴

• Persistent muscle weakness (myopathy) occasionally occurs in late childhood or adolescence
• Fatigue that can restrict play, mobility, or engagement in physical education
• Delayed motor development and achievement of milestones
• From time to time, hepatomegaly, deafness, visual changes, and short stature may occur

Muscle weakness is generally gradual and progressive. It involves the muscle groups near the body (proximal weakness) and occasionally involves facial or swallowing muscles. Severity may range: some individuals have mild fatigue, whereas others require assistance with walking, eating, or doing daily activities.¹

Mechanism of disease of lipid accumulation in muscle fibres

The cause of muscle weakness in CDS is the misplacement of lipid droplets. Under normal circumstances, muscle fibres retain trace amounts of fat for energy, but they counteract this by having the machinery to burn it. In CDS, the cellular machinery to degrade triglycerides is lost. As a consequence, small fat droplets accumulate gradually, compressing and deforming muscle fibres. The muscle cells are congested and no longer maintain their normal appearance and function. Microscopic examination of biopsies shows muscle fibres filled with these droplets. Gradually, this accumulation results in prolonged energy deficits in muscles. The cells cannot contract effectively, leading to clinical weakness and enhanced fatigue on exertion.¹

There is also evidence that inflammation and rapid breakdown of the muscle cells can be triggered by swelling of the muscle cells. Inability to burn fat for energy leaves the muscle with less energy stores, so even minor activities make patients with CDS extremely fatigued. Further damage is also caused by stress from these accumulations to other cellular structures, further weakening muscles.⁵

Supportive treatment for muscle weakness in CDS

Nutritional interventions

Nutrition is the main area of supportive care in individuals with CDS. The aim is to limit new fat storage and enable the body to utilise safer forms of energy. The most widely suggested strategy is a diet that is low in long-chain fats and rich in medium-chain triglycerides (MCTs). MCTs can be broken down and utilised as energy without the faulty pathway that necessitates ABHD5, effectively circumventing the defect in fat metabolism.⁶ 

Key aspects of dietary intervention:

1. A low-fat diet restricting long-chain triglycerides
2. Supplementation with MCT oil as a source of alternative energy
3. Regular monitoring for deficiency of vitamins, particularly fat-soluble vitamins
4. Adjustments according to liver function, growth, and nutritional needs

Physical therapy interventions

Physical therapy (PT) is generally a cornerstone in the treatment of muscle weakness in CDS. The primary objectives are to preserve muscle strength, enhance endurance, preserve flexibility, and avoid contractures that may arise as muscles weaken.⁵

Individuals with CDS should avoid high-intensity or strenuous exercise that can cause muscle damage. Muscle weakness is potentially dangerous, placing them at risk for rhabdomyolysis (muscle fibre breakdown that can cause kidney damage). Any exercise or physical therapy program should be customised and closely monitored for safety.^5,7

Speech therapy for errors and swallowing issues

Certain individuals with CDS also experience weakness in the muscles involved in speech and swallowing, a category referred to as the "bulbar" muscles. Weakness can manifest as slurred speech (dysarthria), swallowing difficulty (dysphagia), or food and liquid aspiration (going down the airway). A speech-language pathologist (SLP) intervenes to evaluate the issues and create strategies for management.

Psychological support for rare disease patients

Having a rare disease such as CDS may, in addition to physical manifestations, involve more than mere physical symptoms. The psychological weight, coping with a "different" body, living with uncertainty, and the social consequences of overt disabilities can be tremendous. Loneliness, worry, depression, and exhaustion are all frequent.⁸

Psychological support may manifest in numerous ways, such as:

• Access to a therapist or psychologist who understands the issues of rare disease
• Join peer support groups, either in person or online, to discuss experiences and strategies
• Family therapy to help parents, siblings, or caregivers adapt and support one another
• Stress management techniques, resilience building, and enhancing self-esteem

Getting help is hard, particularly with the stigma around mental health or the sense of alienation. But getting those needs met directly, with the support of professionals, improves quality of life, enhances physical therapy participation, and makes every other part of care more efficient. For kids, involving school counsellors or social workers as members of the care team is particularly beneficial.⁸

Patient perspectives and quality of life in CDS rehabilitation

Individuals with CDS, and their families, grapple with issues that extend well beyond the medical. Day-to-day challenges of symptom management, therapy visits, coping with a healthcare system that might know little about the disease, and managing school or work can be daunting.⁸

Patient accounts repeatedly identify a need for independence, dignity, and engagement in their preferred activities, goals that are aimed to be facilitated through supportive therapies. Effective rehabilitation helps individuals retain their self-worth, socialise, and pursue hobbies or learning opportunities. It also assists in accommodating transformations that occur with time, like the necessity for mobility support or other forms of communication.⁸

Rehabilitation guidelines for lipid storage myopathies

Even though formal, internationally accepted guidelines for CDS are currently under development, experience from similar lipid storage myopathies, diseases that, like CDS, interfere with muscle metabolism and lead to weakness, is frequently drawn upon by clinicians.⁹

Overall principles for rehabilitation for these diseases are:

• Prompt, proper intervention: Begin physical and occupational therapy once muscle involvement has been found
• Do not overdo it: Begin measures to prevent muscle rupture
• Watch for secondary complications: joint contractures, scoliosis, or breathing difficulties
• Adjust to evolving needs: Apply greater support as independence diminishes, but always push for utmost involvement

For most individuals, therapy is lifelong and adapts to age or disease course. The guidelines are strong in stressing the value of an integrated, patient-centric model that adapts to each person's evolving needs.^8,9

Summary

Chanarin-Dorfman Syndrome (CDS) is a multifaceted, lifelong disorder that can significantly influence muscle strength and health. Although the storage of fat in muscles, liver, and skin is associated with a single gene mutation, its impact extends throughout the body and brain. The disease has no cure; however, by focusing on supportive therapies, such as proper nutrition, physical and occupational therapy, speech and swallowing therapy, mental health treatment, and particularly team-based (multidisciplinary) management, individuals with CDS can lead a good quality of life.