Sarcoid Myopathy - A Rare Disorder

Introduction

The human body is equipped with various biochemical reactions that fight against infections. When various factors disrupt these reactive cells, they begin attacking normal tissue. One such disease is caused due to immune response resulting in sarcoidosis. Sarcoidosis is an inflammatory condition where the immune system attacks the body, affecting multiple organs. The etiology of this response is unknown. Lungs are the primary organ affected, followed by musculoskeletal, nervous, and cardiac tissue. When muscles get attacked by reactive cells, it is termed sarcoid myopathy. Asymptomatic involvement is seen in most cases, while clinical manifestation can be seen in less than 0.5 to 2.3 % of patients.

What Is Sarcoid Myopathy?

Sarcoid myopathy is where sarcoidosis affects muscle tissue, leading to muscle weakness and fatigue. Proximal muscles are most affected, followed by the diaphragm, intercoastal, extraocular, pharyngeal, and endomyocardial muscles. Individuals with this condition are intolerant to exercise. However, most of the patients show remission without any treatment.

What Are the Causes of Sarcoid Myopathy?

The causes of the disease are unknown, but studies have attributed it to genetic factors and infectious and environmental agents that trigger inflammatory responses and granuloma formation.

• Women in the older age group are susceptible.

• African- Americans or blacks have a higher incidence than other races.

• Individuals with a familial history of sarcoidosis are most susceptible to the disease.

What Are the Types of Sarcoid Myopathy?

Based on clinical manifestations, sarcoid myopathy is classified into four types:

1. Nodular Type - In this type, clinically palpable lymph nodes and myalgia are present in muscle extremities. There is no loss of motor functions. Large lesions may resemble tumors. Commonly found among African- Americans during the onset of the disease. Lower limbs are commonly affected.

2. Chronic Myopathic Type - Chronic myopathy is the most common type of sarcoid myopathy, predominantly in older women. It has symmetrically affected proximal muscle, leading to hypertrophy and atrophy. The condition presents with systemic involvement and gradually progresses, affecting multiple organs. Remission is not seen only with steroids and periods of remission and exacerbation during treatment.

3. Acute Myositis Type - Acute myopathy is the least common sarcoid myopathy. Clinical manifestation includes bilateral muscular swelling and pain, progressing to muscular contracture, hardening, and hypertrophy. It is most common among young women of less than 40 years. Fatigue, fever, and joint symptoms can be seen. Elevated muscle enzymes in the blood are present.

4. Smoldering Type - Smoldering myopathy is a newly described form of sarcoid myopathy. Characteristics include constant myalgia without nodules, motor deficits, or amyotrophy. Most common among the elderly. Skeletal and ophthalmic involvement is common.

What Are the Symptoms of Sarcoid Myopathy?

The muscle disorder is associated with

• Fever.

• Myalgia (pain in muscles).

• Polyarthralgia (pain in joints).

• Erythema nodosum (painful nodules under the skin).

• Dysphagia (difficulty swallowing).

• Nerve palsy.

• Generalized weakness and fatigue.

• Respiratory failure due to the involvement of intercostal muscles, diaphragm, and pharyngeal muscles may be seen.

How Is Sarcoid Myopathy Diagnosed?

Since symptoms and types of disease vary from patient to patient, there is a chance of overlapping symptoms. Hence, an accurate diagnosis is required.

1. Medical history and physical examination are a must.

2. Laboratory tests such as blood count, differential WBC (white blood cells), electrolyte sedimentation rate (ESR), and C-reactive protein (CRP) are useful in diagnosis.

3. Magnetic Resonance Imaging (MRI)

• In the nodular type of myopathy, a star-shaped central area of low signal intensity surrounded by areas of high signal intensity is seen. Studies show the dull central area as fibrous tissue and the surrounding bright area as inflammatory cells.

• Homogenous bright signal intensity is seen in chronic myopathy.

• In acute myopathy, there is a diffuse increase in signal intensity.

• MRI is normal in the smoldering type of myopathy.

4. Positron emission tomography (PET) scanning measures signal uptake in affected areas in asymptomatic cases. PET scans, along with dyes, are used to assess the extent of the disease, identify the occult site of disease involvement, and guide the site for biopsy.

5. Gallium scanning measures an increase in radionuclide uptake by acute myopathy, depending on the severity of inflammation.

6. Computed tomography (CT) scans areas of muscle atrophy.

7. Electromyography (EMG)is used to assess myopathic changes.

8. Muscle biopsy is done, as most cases present with granuloma in muscle fibers.

What Are the Histopathological Features?

Presence of non-caseating granulomas with a mass of epithelioid cells and multinucleated giant cells. Granuloma is surrounded by lymphocytes and contains minimal to no central necrosis. Asteroid bodies and Schaumann bodies may be present. Muscle fibrosis is seen, followed by degeneration and regeneration due to muscle fibers adjacent to the granuloma being compressed.

What Is the Tiger Man Sign?

PET scan done with F-18 fluorodeoxyglucose dye reveals dye uptake in bilateral lung fields, mediastinal lymph nodes, and numerous sites of patchy linear uptake in skeletal and cutaneous tissue, which gives an appearance similar to that of the stripes of the tiger.

What Are the Treatment Options?

Studies are ongoing, and no specific treatment is available due to unknown etiology. Therefore, most of the cases resolve on their own without treatment. However, if the disease persists, symptomatic management is done with the help of steroids and immunosuppressants.

Medications:

Medication is used to reduce inflammation and prevent organ damage.

1. Corticosteroids such as Prednisone and Cortisone are used. They are the first line of treatment.

2. Immunosuppressants such as Methotrexate reduce organ damage and inflammation.

3. Anti-tumor necrosis factor-alpha antibodies (anti-TNF- alpha antibodies) such as Infliximab target specific immune system chemicals to reduce inflammation. It is given through infusion in veins. They help treat sarcoidosis that does not respond to other lines of treatment.

4. Nonsteroidal anti-inflammatory drugs (NSAIDs) are prescribed for prolonged use. It provides temporary relief from symptoms.

5. Hydroxychloroquine may be useful when elevated calcium levels are present in the blood.

6. Another treatment, such as physiotherapy, is needed in case of fatigue and to improve muscle strength.

7. Acute myopathy shows improvement with systemic treatment, whereas chronic myopathy does not show improvement and causes a debilitating condition.

What Is the Prognosis?

The prognosis is generally good for the disease. Individuals recover with or without treatment within a few years. However, in individuals with persistent symptoms, it can lead to complications with multiple organs, which require prolonged treatment with steroids and their adjuncts.

What Are the Lifestyle Changes Suggested?

• Patients have to take medicine at the doctor's recommendation.

• Patients must maintain healthy eating habits with a balanced diet.

• Individuals with sarcoid myopathy must achieve adequate sleep and a stress-free environment.

Conclusion

Sarcoidosis, a rare disease, lacks sufficient research and evidence regarding the course of the disease and treatment options. Most cases do not require any treatment as they enter remission without treatment. However, if symptoms persist, adequate care is recommended. The nature and severity are highly variable and need proper long-term study.