What Is Sjögren’s Syndrome?

Sjögren’s syndrome is an autoimmune disease that is more common in women than in men, and usually develops between the ages of 45 and 55 years. The cells in your body have molecules on their surfaces that the immune system usually recognizes as “self-antigens” (in other words, it recognizes them as “not foreign” and therefore not potentially dangerous).

However, sometimes the body’s immune system starts to recognize self-antigens as foreign ones and begins to attack them. When this happens, the inflammation caused by the “autoimmune” response can result in the destruction of normal, healthy body tissue, or changes in the function or growth of an organ.

What Causes Sjögren’s Syndrome?

The exact causes of Sjögren’s syndrome are not yet understood, but it mainly affects “exocrine” glands, particularly the ones that produce tears (the lacrimal gland) and saliva (the salivary gland). Exocrine glands are organs in the body that produce and release substances through ducts (openings), and include the glands that release milk, digestive juices, tears, and sweat.

Although Sjögren’s syndrome is mainly associated with having dry eyes and a dry mouth, it is a systemic disease (a condition that affects the whole body rather than a single body part or organ) because the long-term (chronic) inflammation that causes it often occurs in other organ systems as well. Patients can experience tiredness, skin rashes (particularly after they have been out in the sun) and dry skin, pain in the muscles or joints, vaginal dryness, and swollen salivary glands.

For some people, Sjögren’s syndrome develops in isolation and is referred to as “primary” Sjögren’s syndrome. For others, its development can be associated with another related autoimmune condition, such as rheumatoid arthritis, and is referred to as “secondary” Sjögren’s syndrome. One reason that Sjögren’s syndrome is difficult to diagnose is that symptoms of constant dryness in areas of the body are not uncommon, particularly as people age, and can vary widely between one person and another.

To be able to diagnose Sjögren’s syndrome, healthcare practitioners look for evidence that an autoimmune response is causing the patient’s symptoms, often by measuring the levels of particular antibodies in blood samples. If there is no evidence that the dryness symptoms are being directly caused by an autoimmune response the symptoms are classified as “sicca” (which literally means “dry”) syndrome. It is worth noting that patients with other autoimmune conditions, such as rheumatoid arthritis and lupus erythematosus, can also experience dryness of the eyes and mouth.

How Is Dryness of the Eyes and Mouth Linked to Cancer Treatment?

Severe mouth and eye dryness are known side effects of some anticancer treatments, with approximately 9.4% of cancer patients who receive chemotherapy treatment developing them. Chemotherapy targets and kills rapidly dividing cells like cancer cells, but can also affect other cells in the body that divide rapidly, causing side effects. Patients with cancer who are treated with immunotherapy experience fewer adverse events (these are unintended and undesirable effects that develop after exposure to a medicine, although they may not have been caused by it) compared with patients treated with platinum-based chemotherapy.

Immunotherapy is a type of treatment that uses the body’s own immune system to tackle a cancer. For example, some immunotherapy medicines target and block a protein called PD-1. PD-1 is found on the surfaces of some immune cells and plays a role in preventing autoimmune responses from developing. Blocking PD-1 triggers these immune cells to find and kill cancer cells.

Although some adverse events that can occur during or after immunotherapy treatment are well known and are routinely looked for by patients’ healthcare teams, others are extremely rare and can have symptoms that are difficult to diagnose and interpret. This can lead to delays in diagnosis and patients receiving treatment for these symptoms.

Approximately 5.3% of cancer patients treated with immunotherapy develop symptoms of dryness of the mouth and eyes because the immune system starts to attack normal, healthy cells as well as the cancerous ones. Where this occurs, the signs and symptoms are different to those of primary Sjögren’s syndrome. Around 50% of all cases of mouth and eye dryness that are linked to immunotherapy occur in men, as opposed to only around 5% for primary Sjögren’s syndrome, and the average age of diagnosis is around 10 years older.

What Does This Case Report Describe?

In this case report, a type of study that looks in depth at the case of a single individual or a specific group of patients, the authors describe the case of a 71-year-old woman who was eventually diagnosed with Sjögren’s syndrome after receiving immunotherapy treatment for non-small cell lung cancer. Case reports are useful because they enable healthcare practitioners to communicate information about rare or previously unreported conditions, complications, or treatments to the rest of the medical community. The authors report that the case of this woman’s experience is unusual because she developed Sjögren’s syndrome only 18 months after her immunotherapy treatment began, and because she developed a broad range of signs and symptoms of the condition.

After 18 months of receiving immunotherapy treatment, the woman’s non-small cell lung cancer was in partial remission (this means that the cancer had reduced in size or stopped growing) and the immunotherapy was stopped. She had been experiencing some mild side effects from the immunotherapy and these had been treated with low-dose steroid treatment. However, once the steroid treatment ended, she quickly started to experience an extremely dry mouth that made swallowing difficult, resulting in her rapidly losing weight. She also developed severe dry eye syndrome (known as “xerophthalmia”) and a type of skin inflammation called “erythema nodosum”, which results in painful reddish lumps developing under the skin, usually on the shins.

In the case of this patient, evaluation by a dermatologist (a doctor that specializes in conditions that affect the nails, hair and, skin) and a rheumatologist (a doctor that specializes in chronic inflammatory conditions like Sjögren’s syndrome, rheumatoid arthritis, and lupus erythematosus) meant that her symptoms were diagnosed correctly as Sjögren’s syndrome. She was able to receive the treatment that she needed (corticosteroid treatment) and her symptoms rapidly improved.