Sarcoidosis

What is sarcoidosis?

Sarcoidosis is a multisystem granulomatous disease. This means there are scattered collections of mixed inflammatory cells (granulomas) affecting many different parts of the body. Characteristically these are non-caseating epithelioid granulomas (a pathological description distinguishing sarcoidal granulomas from the caseating or cheese-like granulomas seen in tuberculosis).

Sarcoidosis usually starts in the lungs or lymph nodes in the chest. It is thought that inflammation of the alveoli (tiny sac-like air spaces in the lungs where carbon dioxide and oxygen are exchanged) is the start of the disease process in the lungs. This may either clear up on its own or lead to granuloma formation and fibrosis (scarring). Over 90% of patients have some type of lung problem. Once considered a rare disease, sarcoidosis is now the most common of fibrotic lung disorders.

Other commonly affected organs (i.e. outside the lungs) include the following:

• Skin 20–35%
• Eye 20–30%
• Liver 30–40%
• Heart 5–25%
• Nervous system 1–5%
• Musculoskeletal 2–38%.

Who is at risk of sarcoidosis?

Sarcoidosis occurs worldwide, affecting persons of all races, age, and sex.

• The risk appears to be greater if you are of African-American, Scandinavian, German, Irish or Puerto Rican descent.
• Mainly affects people between 20-40 years of age.
• Risk is two times greater in black women than in black men.

What causes sarcoidosis?

Not much is known about sarcoidosis and to date, there is no known cause or causes. It is thought to be a disorder of the immune system where there is a malfunction in the body's natural defence mechanisms. Whether this abnormal immune response is a cause of sarcoidosis or an effect of the disease still needs to be answered.

Continued research is necessary to answer remaining questions such as:

• Is sarcoidosis triggered by a hypersensitivity response to one or many agents (bacteria, virus, fungi, chemical toxin)?
• In which body organ does sarcoidosis actually start?
• Do hereditary, environment, and lifestyle play a role in how the disease presents and progresses?
• How can sarcoidosis be prevented?

What are the signs and symptoms of sarcoidosis?

Sarcoidosis may not result in symptoms and the disease may come and go without the patient or doctor ever being aware of it. Symptoms can appear suddenly and then just as quickly resolve spontaneously. Sometimes, however, they can continue over a lifetime.

Symptoms can be related to the specific organ affected, or they can be non-specific general symptoms, including:

• weight loss
• loss of appetite
• fatigue
• fever
• chills and night sweats.

Sarcoidosis may involve one organ system or several.

Sarcoid plaques

Sarcoid on knee

Sarcoid granulomas

Lupus pernio

Sarcoid papules

Sarcoid nodules

Enlarged lymph nodes

How is sarcoidosis diagnosed?

There is no single or specific diagnostic test for sarcoidosis. The following tests may be performed when sarcoidosis is suspected.

These tests will not only be used to help confirm the diagnosis but can also help the doctor to monitor the progress of the disease over time and determine whether the condition is improving or deteriorating.

What is the treatment for sarcoidosis?

For most patients with sarcoidosis, no treatment is required. Symptoms are usually not disabling and tend to disappear spontaneously. In mild-to-moderate cases, because the disease can resolve on its own spontaneously, a 3 months observation period is recommended before commencing any treatment. When treatment is necessary the aim is to keep the lungs and other affected organs functioning and to relieve symptoms.

In most patients initial treatment is with corticosteroids; these are used to treat inflammation and granuloma formation. Prednisone is the most often prescribed corticosteroid. This may need to be continued for several years as the disease can often relapse once treatment stops.

If prednisone fails to improve symptoms, other immune-modifying agents such as methotrexate, azathioprine, hydroxychloroquine or tetracyclines may be used.

Eye and skin lesions may be managed with topical corticosteroids (eye drops, creams or injections). Laser surgery has been used in treating disfiguring skin plaques and lupus pernio.

Success in individual cases has been reported with allopurinol, isotretinoin, leflunomide, pentoxifylline, infliximab,  thalidomide and JAK kinase inhibitors (eg, tofacitinib).

It is often difficult to know when to start treatment, what drugs and dose to prescribe, and how long to treat for, as the disease can often resolve without any treatment. The decision depends on the organ systems involved and how far the inflammation or granuloma formation has progressed.

Monitoring the disease is essential as treatment can then be modified accordingly.

How serious is sarcoidosis and what is the prognosis?

In general, sarcoidosis appears briefly and resolves without relapse in most cases. 20-30% of patients are left with some permanent lung damage and 10-15% develop chronic sarcoidosis that may last for many years.

In 5–10% of cases, the disease can become fatal if either granulomas or fibrosis seriously affects vital organs such as the lungs, heart, nervous system, liver or kidneys. End-stage lung disease may need lung transplantation.

Cutaneous sarcoidosis usually has a prolonged course. Papules and nodules tend to resolve over months or years, whilst plaques may be more resistant. Lupus pernio is often present in patients with chronic fibrotic sarcoidosis and is associated with involvement of the upper respiratory tract, advanced lung fibrosis, bone cysts and eye disease.

With correct diagnosis and proper management, most patients with sarcoidosis continue to lead a normal life.