SJÖGREN’S SYNDROME

Identifying Sjögren’s Syndrome

The what, where, why, and how of diagnosing this condition.

By Melissa Barnett, OD, FAAO

The European-American consensus group classified two forms of Sjögren’s syndrome. Primary Sjögren’s consists of aqueous-deficient dry eye, dry mouth in combination with autoantibodies, reduced salivary secretion, and a positive focus score on minor salivary gland biopsy (Vitali et al, 2002). Secondary Sjögren’s consists of all of the classifications of primary Sjögren’s combined with autoimmune connective tissues disease, most commonly rheumatoid arthritis. Nine out of 10 patients who have Sjögren’s disease are women. In Sjögren’s syndrome, the lacrimal and salivary glands are targeted by circulation antibodies in an autoimmune process directed against muscarinic receptors within the glands (Zoukhri, 2006).

Aqueous-deficient dry eye and dry mouth are hallmarks of Sjögren’s. Ocular surface disease in Sjögren’s syndrome results from disease of the lacrimal functional unit (LFU) (Pflugfelder, 2014). The LFU is composed of ocular surface tissues (cornea, conjunctiva, and conjunctival blood vessels), the main and accessory lacrimal glands, the meibomian glands, conjunctival goblet and epithelial cells, and their neural connections. This network connects the sensory tissues and secretory glands that provide homeostasis of the ocular surface.

The LFU receives input from sensory nerve endings in the cornea, conjunctiva, and eyelids (Stern et al, 1998; Stern et al, 2013). Inflammation in the lacrimal gland can lead to foreign body sensation, keratoconjunctivitis sicca, altered tear composition, and tear instability. Chronic inflammation and interruption in the feedback between various components in Sjögren’s syndrome may cause dysfunction or death of tear-secreting epithelium in the lacrimal gland and conjunctiva.

There are numerous mechanisms for lacrimal gland dysfunction in Sjögren’s syndrome. These include cholinergic blockade from autoantibodies to muscarinic acetylcholine receptor 3, inhibition of acinar secretion by inflammatory cytokines such as IL-1, cytokine-mediated epithelial cell death, or replacement of acini by lymphocytes (Humphreys-Beher et al, 1993; Kovacs et al, 2005; Zoukhri et al, 2007; Rahimy et al, 2010; and others. Full list available at www.clspectrum.com/references).

Multiple substances are produced by the lacrimal gland that support and protect the ocular surface (Alex et al, 2013). These include epidermal growth factors (EGFs), antimicrobial factors (e.g., lactoferrin, defensins), anti-inflammatory factors (e.g., IL-1RA), and mucins. The tears of patients who have Sjögren’s syndrome have reduced concentrations of these substances.

Inflammatory mediators that cause ocular surface epithelial disease in Sjögren’s include the matrix metalloproteinases (MMPs), inflammatory cytokines, and T helper (Th) cell-associated cytokines. Increased production of MMP-3 and MMP-9 by ocular surface cells has been observed in Sjögren’s syndrome (Sobrin et al, 2000; Chotikavanich et al, 2009).

Systemic Manifestations There are numerous systemic manifestations of Sjögren’s including in the mouth and skin, neurological, cardiovascular, and in the central nervous system. Table 1 lists the extensive systemic symptoms.

Ocular Symptoms Henrik Sjögren (1933) first described aqueous-deficient dry eye as an ocular finding in patients who have primary Sjögren’s disease. Ocular symptoms in patients who have Sjögren’s include eye irritation (foreign body sensation), which is constant and can affect quality of life, and photophobia due to tear dysfunction and ocular surface disease (Uchino and Schaumberg, 2013). Other ocular symptoms include dryness, pain, stinging, burning, itching, epiphora, and blurring or interrupted vision. It has now been demonstrated that clinically significant ocular surface disease in Sjögren’s syndrome patients may be present with normal tear production and tear volume (Pflugfelder, 2014).

How Is Sjögren’s Syndrome Diagnosed?

Sjögren’s syndrome has been diagnosed with autoantibodies as diagnostic markers. Specifically, anti-Ro/SSA, anti-La/SSB, and anti-nuclear antibodies (ANAs) are elevated in patients who have Sjögren’s syndrome (Chen et al, 2009). SS-A (or Ro) and SS-B (or La) are the marker antibodies for Sjögren’s syndrome. A positive SS-A is found in 70% of Sjögren’s patients; a positive SS-B is found in 40% of Sjögren’s patients (Reichlin, 2008).

ANAs are a group of antibodies that react against normal components of a cell nucleus. About 70% of Sjögren’s patients have a positive ANA. Rheumatoid factor (RH) is positive in many rheumatic diseases. This antibody test is performed for the diagnosis of rheumatoid arthritis (RA), but is positive in 60% to 70% of patients who have Sjögren’s. Erythrocyte sedimentation rate (ESR) measures inflammation. An elevated ESR indicates the presence of any inflammatory disease, including inflammation in Sjögren’s syndrome. Immunoglobulins (Ig) are normal blood proteins that are involved in immune reactions; these are elevated in Sjögren’s patients.

Genetic Testing

Sjö A new test for Sjögren’s syndrome from Nicox SA, Sjö tests for the traditional biomarkers of Sjögren’s. In addition, three novel, proprietary biomarkers are tested. These are salivary protein-1 (SP-1; IgA, IgG, IgM), carbonic anhydrase 6 (CA6; IgA, IgG, IgM), and parotid secretory protein (PSP; IgA, IgG, IgM). All three of these biomarkers provide high specificity and sensitivity for the early detection of Sjögren’s syndrome. A Sjö test is performed by obtaining a blood sample with a finger prick, applying the sample to a collection card, and then sending the card to be analyzed.

Recent studies have indicated additional autoantibodies in Sjögren’s syndrome to SP-1, CA6, and PSP-1 (Shen et al, 2012). Autoantibodies were present in two animal models for Sjögren’s syndrome and occurred earlier in the course of the disease. Patients who have Sjögren’s also produced antibodies to SP-1, CA6, and PSP. Antibodies were found in 45% of patients meeting the criteria for Sjögren’s syndrome who lacked antibodies to Ro or La. Thus, SP-1, CA6, and PSP may be useful markers for identifying patients who have Sjögren’s syndrome at early stages of the disease or those who lack antibodies to either Ro or La.

Genetic and Environmental Risk Factors There have been numerous advances in our knowledge of Sjögren’s syndrome. A variety of genetic and environmental risk factors as well as cellular and molecular pathways have been identified. This new knowledge can provide multiple targets for new therapies. In addition, advances in technology in the past 10 years have led to innovations in genetics, genomics, and epigenetic research. An example is the characterization and analysis of DNA and RNA in patient samples on a genome-wide scale. These new techniques will help to identify additional risk factors for the diagnosis and treatment of Sjögren’s syndrome.

The relationship between primary Sjögren’s syndrome and mucosa-associated lymphoid tissue lymphomas is well established (Risselada et al, 2014; Theander et al, 2011). Clinical and immunological characteristics have been described as lymphoma predictors in several studies. Recent studies report a predominance of diffuse large B-cell lymphomas (Giannouli and Voulgarelis, 2014). There are distinct differences in both disease severity and prognosis among patients who have various types of lymphoma. It is important to identify the risk factors that can predict the development of subtypes of lymphoma, because the outcome and clinical behavior of lymphoma is affected by a range of biological variables. Biological and molecular advances can lead to potential novel therapies for Sjögren’s syndrome.

There are numerous viruses that have been associated with Sjögren’s. It is unclear whether viruses start or perpetuate Sjögren’s syndrome. Recent data indicates that a viral infection is linked with tertiary lymphoid structures (TLS) in the salivary gland. This suggests that viral–host interactions may lead to the development of autoimmunity in Sjögren’s (Lucchesi et al, 2014).

Viruses might provide a link between interferon (IFN) production and the IFN signature (the expression of type I IFN-inducible genes) that is present in responding cell types (Brkic and Versnel, 2014). Type I IFN consists of many different subtypes and is not easily measured using conventional enzyme-linked immunosorbent assay (ELISA) testing. Salivary gland tissue and blood can indicate type I IFN activity. IFN type I could serve as a novel biomarker in the pathogenesis of Sjögren’s syndrome. This information could define disease activity, sub-classification of patients, and how a patient responds to therapy. In addition, IFN type I could be used as a target for therapeutic intervention.

Ocular Testing

It is important to note that primary and secondary Sjögren’s syndrome can present with any form of dry eye. There are numerous tests to evaluate the ocular surface in Sjögren’s syndrome.

Schirmer’s Test The Schirmer’s test is used to evaluate aqueous tear production. It is helpful in assessing patients who have clinical signs and/or symptoms of dry eye. A Schirmer’s test uses a special filter paper (Whatman Grade No. 41), which is 5mm wide and 35mm long. Schirmer 1 is performed with anesthetic, and Schirmer 2 is performed without it. In theory, both Schirmer 1 and 2 evaluate baseline secretion; Schirmer 2 also measures reflex secretion. A Schirmer’s test is performed by placing a Schirmer’s strip under the lower lid. After five minutes, the results are analyzed. A test result of greater than 10mm of moisture on the filter paper in five minutes is normal.

Phenol Red Thread Tear Test Another method to evaluate tear production is the Phenol red cotton thread tear test (Zone-Quick, Menicon). This test takes 15 seconds per eye and requires no anesthetic. The color change in the cotton thread can be confirmed hours after testing.

Fluorescein Clearance Test A newer test of aqueous tear production is the fluorescein clearance test. While this test may be more accurate, it is rarely performed in clinical practice. The fluorescein clearance test measures the clearance of a fixed amount of fluorescein dye instilled into the eye after intervals of time using fluorophotometry. Dry eye causes delayed clearance of fluorescein. The rate of clearance relates to tear production. First, 5ml of 2% sodium fluorescein is instilled. Then, after 15 minutes, the color of the lateral tear meniscus is matched to a scale. A value of three is the threshold between normal and symptomatic.

Ocular Staining Ocular staining is performed using fluorescein, rose bengal, and lissamine green dyes. Fluorescein stains defects in the corneal and conjunctival epithelium. A wet fluorescein strip is applied to the conjunctiva to evaluate staining.

Rose bengal is used to stain dead conjunctival cells or cells unprotected by the normal mucin layer. Rose bengal stains the conjunctiva more than the cornea. This correlates well with the degree of aqueous tear deficiency, tear breakup time, and reduced mucus production by conjunctival goblet cells and non-goblet epithelial cells. Rose bengal is available in a strip or 5ml bottle of 1% rose bengal. The downside of this stain is that it may irritate the ocular surface.

Lissamine green has the same mechanism as rose bengal; however, it is less irritating. A wet lissamine green strip is applied to the conjunctiva to evaluate staining.

InflammaDry Detector InflammaDry (Rapid Pathogen Screening, Inc.) is a test that is similar to an at-home pregnancy test (Chotikavanich et al, 2009). InflammaDry takes a sample of a patient’s tears and gives a positive (ocular surface disease) or negative (no ocular surface disease) result. The test is 10 minutes in duration. A red line indicates elevated MMP-9. A stronger red line indicates more significant ocular surface disease. The test is based on a quantifiable value of the amount of MMP-9 in the tears. Greater than 40ng/ml of MMP-9 indicates a positive InflammaDry test. MMP-9 is a proteolytic enzyme from stressed epithelial cells on the ocular surface and is a non-specific marker of inflammation. These are cells that have been subjected to dry eye. The InflammaDry test does correlate with dry eye, ocular surface disease, and some clinical findings. More positive results are associated in both Sjögren’s syndrome and meibomian gland dysfunction.

Impression Cytology Impression cytology is a method of collecting conjunctival epithelial cells for analysis of ocular surface disorders. A cytology membrane is pressed against the conjunctival surface, removed, and then stained with periodic acid Shiff or antibodies. The analysis includes shape, number, density, and pathologic modifications of epithelial cells, goblet cells, and inflammatory cells. Although impression cytology provides information about ocular surface disease, it is not practical for clinical practice.

Tear Osmolarity Tear osmolarity is important for many aspects of epithelial and nerve cell function. In healthy tears, the electrolyte concentrations are maintained to ensure correct osmolarity. However, in unhealthy tears, proteases are activated, which degrades the extracellular matrix and the tight junctions between adjacent cells of the corneal epithelium. Activated proteases are responsible for cleavage of cytokines into an activated pro‐inflammatory form. A subsequent increase in electrolyte concentration increases tear osmolarity. Elevated osmolarity can cause less regulation of the tear film, more damage to the ocular surface, and more inflammation.

According to TearLab Corporation, its TearLab Osmolarity System measures the osmolarity of proteins in the tears, which is a sensitive marker for dry eye. A 50nl sample of tears is taken in vitro for diagnostic use. Increased rates of tear evaporation lead to a more concentrated tear film (increased osmolarity). Increased tear evaporation is present with both aqueous-deficient and evaporative dry eye disease.

The TearLab Osmolarity Test Card determines tear osmolarity using nanoliter volumes of tear fluid collected directly from the eyelid margin. The system utilizes a temperature-corrected impedance measurement to provide an indirect assessment of osmolarity. After applying a lot-specific calibration curve, osmolarity is calculated and displayed as a quantitative numerical value. Osmolarity values above 308mOsms/L are generally indicative of dry eye disease.

LipiView LipiView was introduced in the United States in 2011 by Tear Science, Inc. LipiView is sold in conjunction with LipiFlow, a device that removes meibomian gland obstructions with direct heat and pressure applied to the eyelid (Qiao and Yan, 2013).

The LipiView system is based on interferometry, which uses interference patterns of waves to make accurate measurements. Light passes through the tear film and into a camera via specular reflection. This creates an interference pattern, which is translated to a colored assessment of the tear film. LipiView measures the absolute thickness of the tear film lipid layer in nanometers. LipiView can help to determine whether a patient has a lipid layer deficiency. The system may also help determine whether the patient would be a good candidate for LipiFlow treatment.

Oculus Keratograph Topography System The Oculus Keratograph Topography System (Oculus Corporation) is capable of non-invasive assessment of tear meniscus height, which is an indicator of ocular surface tear volume. Topography measures the inferior tear meniscus height via imaging of the anterior ocular surface. It projects a small horizontal light that reflects off of the top of the tear meniscus and is able to directly measure the height of the inferior tear meniscus in millimeters. The computer analyzes the reflected Placido ring mires and measures the breakup time throughout the surface measured. Time measures of localized tear breakup are recorded to the 0.10 of a second. Breakup times of greater than 14 seconds are considered normal, whereas between 13 and 8 seconds are considered borderline. Seven seconds and below are considered abnormal.

Oral Tests

Salivary flow measures the amount of saliva produced over a certain period of time. Salivary scintigraphy is a nuclear medicine test that measures salivary gland function. Salivary gland biopsy is typically performed in the lower lip and confirms inflammatory cell (lymphocytic) infiltration of the minor salivary glands. In Sjögren’s syndrome, autoantibodies are produced and lymphocytic aggregates are present in the salivary glands in approximately 25% of patients (Risselada, et al, 2013).

Conclusion

As eyecare providers, we are about to apply novel testing for Sjögren’s syndrome.

With patient history, laboratory, blood tests, ocular testing, and coordination with rheumatology and dentistry for salivary testing, we are able to detect Sjögren’s syndrome. Early detection and treatment of Sjögren’s syndrome is important to prevent lymphoma or other systemic complications. Coordination of care with rheumatology is useful if Sjögren’s syndrome is suspected. CLS

For references, please visit www.clspectrum.com/references and click on document #224.

Dr. Barnett is a principal optometrist at the UC Davis Medical Center in Sacramento. She lectures and has been published on topics including dry eye, anterior segment disease, contact lenses, corneal collagen cross-linking, and creating a healthy balance between work and home life for women in optometry. She is a spokesperson for the California Optometric Association and has appeared on several television shows. She is an advisor to Alcon and Allergan, has received honoraria from Acculens and Essilor, and has performed research for Nidek.