Thyroid-associated ophthalmopathy: clinical features, pathogenesis, and management

Choroidal vascularity index in thyroid-associated ophthalmopathy

OBJECTIVE

To investigate the choroidal vascularity index (CVI) in patients with thyroid-associated ophthalmopathy (TAO) and its relationship with clinical features and clinical activity score METHODS: Right eyes of 53 patients with TAO and 53 healthy subjects were scanned for subfoveal choroidal thickness (SFCT), CVI, choroid-stromal area (C-SA), choroid-luminal area (C-LA), choroidal stromal index (CSI), choroid-stromal-to-luminal-area ratio, and CVI and CSI within the central 1500 µm of the macula (CVI₁₅₀₀ and CSI₁₅₀₀) by enhanced-depth imaging optical coherence tomography. The results of the TAO group and the healthy controls were compared.

RESULTS

The SFCT was significantly greater in the TAO group than in the control group (p = 0.02). The values of C-LA, C-SA, and total choroidal area (TCA) in the TAO group were significantly higher than those in the control group (p = 0.01, p = 0.04, and p = 0.01, respectively). The increases in SFCT, C-LA, C-SA, and TCA were 12.1%, 12.2%, 16.2%, and 13.6%, respectively. There was no statistically significant difference between the groups for CVI, CSI, CVI₁₅₀₀, CSI₁₅₀₀, and choroid-stromal-to-luminal-area ratio (p > 0.05). CVI₁₅₀₀ and CSI₁₅₀₀ have displayed a statistically significant correlation with exophthalmometry and clinical activity score (p < 0.05).

CONCLUSION

The alterations in stromal and vascular structures are proportionally similar in TAO; thus CVI may not be affected significantly. However, CVI₁₅₀₀ and CSI₁₅₀₀ may be associated with disease activity. The choroidal thickening in TAO may be the result not only of vascular mechanisms but also by an increase in stromal contents.

Are Severe Forms of Thyroid Eye Disease Common in the Indian Population? Clinical Characteristics of 136 Patients from a Tertiary Eye Care Centre

Context

Considerable evidence of gender, ethnicity, thyroid dysfunction, and environmental factors including smoking influencing the development and progression of thyroid eye disease (TED).

Settings and Design

Cross-sectional study of the clinical characteristics of 136 patients with TED who presented to the Orbit and Oculoplasty services at a tertiary eye care center in south India between October 2018 and June 2020.

Results

Among the 136 patients (M: 61, F: 75), the mean age was 47.04 (SD ± 13.24) years. Hyperthyroid disease was present in 53%, hypothyroid disease in 40%, and 7.3% were euthyroid. Active disease was noted in 25% and inactive disease in 75% of patients. Active disease was present in 25% of hyperthyroid, 18.5% of hypothyroid, and 15% of euthyroid patients. Active TED showed statistically significant association toward development of greater severity of proptosis (P = 0.001), optic neuropathy (P = 0.004), and extraocular movement restriction (P < 0.001) as compared to inactive disease. Mild, moderate to severe, and sight-threatening TED was noted in 34.6%, 59.6%, and 6% of patients, respectively. Nine eyes had dysthyroid optic neuropathy, of which eight had either mild or no proptosis while one had moderate to severe proptosis.

Conclusion

Prevalence of active as well as severe thyroid eye disease is common in our population. Recommendation for ophthalmological examination of patients even with milder disease especially when associated with decreased vision and signs of inflammation. Active disease is less common in euthyroid patients, thus necessitating maintaining the euthyroid status toward reducing disease activity and progression.

Thyroid Eye Disease

Thyroid eye disease (TED), an autoimmune inflammatory disorder of the orbit, presents with a potential array of clinical sequelae. The pathophysiology behind TED has been partially characterized in the literature. There remain certain elusive mechanisms welcoming of research advances. Disease presentation can vary, but those that follow a characteristic course start mild and increase in severity before plateauing into an inactive phase. Diagnosis and evaluation include careful physical examination, targeted laboratory work up, appropriate imaging studies, and tailored treatment regimens. Special consideration may apply to certain populations, such as pediatric and pregnant patients.

Beyond dry eye: how co-morbidities influence disease phenotype in dry eye disease

Dry Eye Disease (DED) is a complex and multifactorial disorder of tear homoeostasis that results in pain, visual disturbance, and ocular surface damage. It is highly prevalent around the world and is associated with many co-morbidities that may contribute to or exacerbate symptoms and signs of disease and affect disease phenotype. However, DED is not one disease and can manifest with a variety of symptoms and/or signs. In this review, we discuss relationships between various co-morbidities and DED phenotypes. For example, individuals with immune mediated diseases, like Sjögren's Syndrome and Graft versus Host Disease, often present with aqueous tear deficiency (ADDE) in the setting of lacrimal gland dysfunction. Individuals with disorders that affect the periocular skin, like rosacea and seborrhoeic dermatitis, often present with evaporative dry eye (EDE) in the setting of eyelid and/or meibomian gland abnormalities. Individuals with pain related disorders, such as chronic pain syndrome and migraine, often present with ocular pain out of proportion to tear film abnormalities, often with accompanying corneal nerve hypersensitivity. Individuals with diabetes mellitus often present with an epitheliopathy in the setting of decreased sensation (neurotrophic keratitis). While not absolute, understanding relationships between co-morbidities and DED phenotypes can help tailor a therapeutic plan to the individual patient.

Blood Count-derived Immunoinflammatory Markers in Thyroidassociated Ophthalmopathy

Purpose

To investigate the diagnostic and prognostic significance of the blood-count derived systemic immunoinflammatory parameters in patients with thyroid-associated ophthalmopathy (TAO).

Methods

In this retrospective case-control study, the blood-count parameters and neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio, and systemic immune-inflammatory index (SII), thyroid peroxidase antibody, and anti-thyroglobulin antibody were evaluated in 46 patients with TAO and 46 matched controls. The associations of the immunoinflammatory parameters with clinical outcomes were analyzed among TAO patients.

Results

Significant differences were found in NLR, PLR, SII, and lymphocyte count between the controls and the TAO group (p < 0.05 for all). In logistic regression analysis, these inflammatory parameters did not have any prognostic effect on the clinical outcomes of the TAO (p > 0.05 for all). The patients, who needed systemic treatment due to any ocular involvement of TAO during the follow-up period, had significantly lower platelet count (p = 0.001) and PLR (p = 0.02) at the time of initial diagnosis when compared to the no treatment-needed group of the TAO patients. The initial platelet count was significantly associated with the subsequent steroid need due to TAO during the follow-up period (β = −0.02, p = 0.03).

Conclusions

NLR, PLR, and SII may serve as potential inflammatory markers in the identification of the TAO, although they have no evident prognostic significance in TAO. However, the relatively lower platelet count at initial diagnosis may be associated with the need for systemic therapy during the follow-up in patients with TAO.

Evaluation of corneal biomechanical properties on ocular response analyzer and their correlation with the clinical profile of the patients with thyroid-associated ophthalmopathy

Purpose: The study evaluates the corneal biomechanical properties on Ocular Response Analyzer (ORA) and aims to establish their correlation with the clinical profile of patients with TAO.Methods: A tertiary care centre-based cross-sectional observational study was conducted. Eighty patients with stage I and II TAO (EUGOGO classification), categorized as group A, were age and sex matched with 85 controls constituting group B. The disease activity was assessed using clinical activity score (CAS). The thyroid hormonal profile of within one-week duration was recorded for each patient of group A. Mean IOP-GAT (IOP using Goldmann applanation tonometer), IOPg (Goldmann-correlated IOP value), IOPcc (cornea-compensated IOP value), CRF (corneal resistance factor), and mean corneal hysteresis (CH) of group A and B were compared. The variation of CH with disease severity, activity, and thyroid status in group A was evaluated.Results: Mean GAT, IOPg, and IOPcc of group A were significantly higher than that of group B (p < .001). Mean CH of group A i.e the visco-elastic dampening ability of cornea was significantly lower than that of group B (p < .001). In group A, mean CH of patients with stage 1 disease severity and CAS<3 was significantly higher than that of patients with stage 2 severity and CAS≥3 (p < .001). CH of hyperthyroid patients was significantly lower than CH of hypothyroid patients (p < .01).Conclusion: TAO affects the biomechanical properties of the globe as reflected by the corneal biomechanics on ORA. The disease severity, activity, and hyperthyroid status are negatively correlated with the CH.

Local Ocular Surface Alterations in Children with Hashimoto's Thyroiditis

PURPOSE

To evaluate the ocular surface characteristics based on Schirmer's test, tear break-up time (TBUT), and conjunctival impression cytology (CIC) in children with Hashimoto's thyroiditis (HT).

METHODS

This study included 51 children with HT and 53 control subjects. The ocular surface characteristics of participants were assessed via Schirmer's test, TBUT, and CIC. Conjunctival samples were examined cytologically according to the Nelson grading system.

RESULTS

Schirmer's and TBUT results were significantly lower in HT group (p < .05). All samples in both the study and control groups were evaluated as grade 0 according to the Nelson classification (p = .841), however, goblet cell density (GCD) was significantly lower in HT group (p = .001). Schirmer test results were significantly associated with the duration of HT (p = .025, r = -0.311).

CONCLUSION

Hashimoto's thyroiditis without any ocular complaints may cause ocular surface changes with TBUT and Schirmer's. Although CIC analysis showed similar grading results, GCD was significantly decreased in HT group.

Choroidal thickness in thyroid-associated orbitopathy

IMPORTANCE

To investigate the choroidal thickness (CT) in patients with thyroid-associated orbitopathy (TAO).

BACKGROUND

To compare CT of TAO patients and healthy subjects.

DESIGN

Prospective cross-sectional study in a public hospital.

PARTICIPANTS

One hundred and four eyes of 52 TAO patients and 52 eyes of 26 healthy subjects.

METHODS

CT was measured with enhanced-depth imaging optical coherence tomography (EDI-OCT) at the subfoveal, macular and peripapillary regions. Multivariate linear regression was used to evaluate the associations of subfoveal CT with systemic and ocular variables among TAO eyes.

MAIN OUTCOME MEASURES

CT of both groups.

RESULTS

CT of eyes with TAO was significantly increased at the subfoveal region, 1 and 2 mm from the fovea nasally, temporally and superiorly, and 1 mm inferior to the fovea (all P < .05). No significant difference was found in CT at 2 mm inferior to the fovea (P = .094) and all four quadrants of the peripapillary region (superior, P = .096; nasal, P = .732; inferior, P = .179; temporal, P = .052). Among TAO eyes, thinner subfoveal choroid was associated with worsening exophthalmos (P = .043), poorer visual acuity (P = .017), increasing age (P = .040) and axial length (P < .001). There was no association between CT and clinical activity score (P = .239).

CONCLUSIONS AND RELEVANCE

TAO patients showed thicker choroid than controls over the macula, but not the peripapillary regions. Thinner subfoveal choroid was associated with worsening exophthalmos and poorer vision. EDI-OCT can monitor choroidal vascular changes associated with TAO and its complications.

Relationship between Clinical and Immunological Features of Thyroid Autoimmunity and Ophthalmopathy during Pregnancy

Problem. Clinical features of Graves' hyperthyroidism (GH) generally improve during pregnancy and rebound in the postpartum period. It is unclear whether the ophthalmopathy that is associated with GH and, less often, Hashimoto's thyroiditis (HT) changes in parallel with the thyroid associated antibody reactions and clinical features or runs a different course. Method of Study. We retrospectively studied 19 patients with autoimmune thyroid disease over 22 pregnancies: 9 pregnancies with GH and 13 with HT. Ophthalmopathy was defined by NOSPECS class. Results. Thyroid peroxidase (TPO) and thyroglobulin (Tg) antibody titres decreased during pregnancy and rose in the postpartum period. During pregnancy, 5 patients with GH and 4 patients with HT developed mild ophthalmopathy and two patients with GH and HT developed new upper eyelid retraction (UER). In the postpartum period, eye scores improved in 3 patients with GH and 3 with HT, remained stable in two and 5 patients, respectively, and worsened in 2 patients with GH and one with HT. Conclusions. In patients with mild to moderate eye signs associated with GH and HT, the orbital and thyroid reactions ran different courses during pregnancy. Since no patient had severe ophthalmopathy, we cannot draw definitive conclusions from this preliminary study.

Novel single-nucleotide polymorphisms in the calsequestrin-1 gene are associated with Graves' ophthalmopathy and Hashimoto's thyroiditis

BACKGROUND

The eye disorder associated with Graves' disease, called Graves' ophthalmopathy (GO), greatly reduces the quality of life in affected patients. Expression of the calsequestrin (CASQ1) protein in thyroid tissue may be the trigger for the development of eye muscle damage in patients with GO. We determined the prevalence of rs74123279, rs3747673, and rs2275703 single-nucleotide polymorphism (SNPs) in patients with autoimmune thyroid disorders, GO, Graves' hyperthyroidism (GH), or Hashimoto's thyroiditis (HT) and control subjects with no personal or family history of autoimmune thyroid disorders. Furthermore, we measured the concentration of the CASQ1 protein in normal and Graves' thyroid tissue, correlating levels with parameters of the eye signs, CASQ1 antibody levels, and the CASQ1 gene polymorphism rs74123279 and rs2275703.

METHODS

High-quality genomic DNA was isolated from fresh blood samples, assayed for identification of rs74123279, rs3747673, and rs2275703 SNPs in CASQ1 gene by MassARRAY SNP analysis using iPLEX technology of SEQUENOM.

RESULTS

DNA samples from 300 patients and 106 control subjects (100 males, 306 females) with GO (n=74), GH (n=130), HT (n=96) and control subjects (n=106) were genotyped for the SNPs rs74123279, rs3747673 (n=405), and rs2275703 (n=407). The SNP rs74123279, rs3747673, and rs2275703 were identified as 1) common homozygous or wild type, 2) heterozygote, and 3) rare homozygous. Minor allele frequency for rs74123279, rs3747763, and rs2275703 were 21%, 40%, and 44%, respectively. Multiple comparisons of genotype frequency for rs74123279, rs3747763, and rs2275703 in the GO, GH, HT, and control groups showed P=0.06, 0.641, and 0.189, respectively. These results were substantiated by multiple comparison of alleles frequency for rs74123279, rs3838216, rs3747763, and rs2275703 in the GO, GH, HT, and control groups showed, P=0.36, 0.008, 0.66, and 0.05, respectively. Pairwise analysis of alleles frequency distribution in patients with GO showed significant probability for rs2275703, P=0.008.

CONCLUSION

Based on their evolutionary conservation and their significant prevalence, we suggest that CASQ1 gene SNPs rs74123279, rs3838216, and rs2275703 may be considered as genetic markers for GO.

Presence of Dry Eye in Patients with Hashimoto's Thyroiditis

Purpose. To evaluate the tear function tests in patients with Hashimoto's thyroiditis and to compare the results with healthy subjects. Methods. A hundred and ten patients with Hashimoto's thyroiditis and 100 healthy subjects were included in this study. The presence of thyroid-associated ophthalmopathy and tear function tests were evaluated clinically. The results were first compared between the patients and the control groups and then compared between patients with NOSPECS and patients without NOSPECS. Logistic regression analyses of the risk factors for dry eye including sex, gender, free plasma thyroxine, proptosis, upper eyelid margin-reflex distance, and duration of the disease were also evaluated. Results. The mean ocular surface disease index score was significantly higher and mean Schirmer and mean tear break-up time scores were significantly lower in patients compared to control subjects. Mean Schirmer and tear break-up time scores were found to be significantly lower in patients with NOSPECS when compared to the patients without NOSPECS. Both proptosis and free plasma thyroxine levels were significantly associated with dry eye. Conclusions. Patients with Hashimoto's thyroiditis tend to develop dry eye more common than healthy subjects. Proptosis and lower free plasma thyroxine levels were found to be risk factors for the presence of dry eye.

Severe thyroid-associated orbitopathy in Hashimoto's thyroiditis. Report of 2 cases

Thyroid-associated orbitopathy (TAO) is characterized by immune-mediated inflammation of the extraocular muscles surrounding orbital connective tissue and adipose tissue. Severe orbitopathy related to autoimmune thyroid disease often occurs in patients with Grave's disease, but it is rare in patients with Hashimoto's thyroiditis. The pathogenesis of TAO is unclear. Several studies have noted a strong correlation between the levels of antibodies to thyrotropin receptor antibody (TRAb) and TAO in Graves' disease. Mild upper eyelid retraction has been reported to be common in Hashimoto's thyroiditis patients, however severe orbitopathy is rare. We report two cases of severe TAO in patients with Hashimoto's thyroiditis who required systemic glucocorticoid therapy and orbital irradiation to treat the TAO. The activity of the TAO was high in both patients, because their clinical activity scores (CAS) for the orbitopathy were high, and magnetic resonance imaging (MRI) showed enlargement of the extraocular muscles and an increase in T2 signal intensity and prolonged T2 relaxation time which indicate an active stage of inflammation. We tested the presence of TRAb by three different assays and were negative in both patients. Since the eye muscle damage cannot be due to TSH receptor antibodies, other pathogenetic mechanisms may be responsible for the orbitopathy in patients with Hashimoto's thyroiditis.

Pathogenesis of thyroid-associated ophthalmopathy: does autoimmunity against calsequestrin and collagen XIII play a role?

Thyroid-associated ophthalmopathy (TAO), or thyroid eye disease, is a complex inflammatory disorder of the eye that, as its name implies, is associated with thyroid disease. TAO can be divided into three subtypes: ocular myopathy, congestive myopathy and mixed congestive and myopathic ophthalmopathy. Although the precise pathophysiology of TAO remains unclear it is likely to reflect an autoimmune reaction involving sensitized T-cells and autoantibodies directed against a thyroid and orbital tissue shared antigen. One well studied candidate in this immune reaction is the thyroid-stimulating hormone receptor (TSH-r), expressed in the orbital fibroblast and pre adipocyte. In our studies of TAO, we have investigated the nature and significance of antibodies targeting other eye muscle and orbital connective tissue (OCT) antigens. Our findings suggest that autoimmunity against the eye muscle antigen calsequestrin and the OCT antigen collagen XIII plays a role in the pathogenesis of TAO. We propose that ocular myopathy and chronic eyelid retraction are due to autoimmunity against skeletal muscle calsequestrin in the extraocular and eyelid muscles, respectively. This may be initiated in the thyroid where calsequestrin expression is upregulated, possibly due to a stimulatory effect of TSH-r antibodies. We also propose that congestive ophthalmopathy results from a reaction against the TSH-r or collagen XIII in orbital fibroblast cell membranes. Further insight into the role of eye muscle and OCT antigens in the pathogenesis of TAO may allow for the development of new therapies to treat the eye disorder and reduce patient morbidity.

Extracellular matrix molecules: potential targets in pharmacotherapy

The extracellular matrix (ECM) consists of numerous macromolecules classified traditionally into collagens, elastin, and microfibrillar proteins, proteoglycans including hyaluronan, and noncollagenous glycoproteins. In addition to being necessary structural components, ECM molecules exhibit important functional roles in the control of key cellular events such as adhesion, migration, proliferation, differentiation, and survival. Any structural inherited or acquired defect and/or metabolic disturbance in the ECM may cause cellular and tissue alterations that can lead to the development or progression of disease. Consequently, ECM molecules are important targets for pharmacotherapy. Specific agents that prevent the excess accumulation of ECM molecules in the vascular system, liver, kidney, skin, and lung; alternatively, agents that inhibit the degradation of the ECM in degenerative diseases such as osteoarthritis would be clinically beneficial. Unfortunately, until recently, the ECM in drug discovery has been largely ignored. However, several of today's drugs that act on various primary targets affect the ECM as a byproduct of the drugs' actions, and this activity may in part be beneficial to the drugs' disease-modifying properties. In the future, agents and compounds targeting directly the ECM will significantly advance the treatment of various human diseases, even those for which efficient therapies are not yet available.

Eye and eyelid abnormalities are common in patients with Hashimoto's thyroiditis

BACKGROUND

Overt ophthalmopathy is presumed to be uncommon in patients with Hashimoto's thyroiditis compared to Graves' disease, where significant eye changes are found in approximately 40% of patients. On the other hand, when observing, more subtle eye changes, particularly upper eyelid retraction (UER) and mild inflammatory signs, may be common in patients with Hashimoto's thyroiditis.

METHODS

We have determined the prevalence and characteristics of eye signs in recently diagnosed patients with Hashimoto's thyroiditis studied prospectively since 2004 till date in Sydney (Australia). We measured serum orbital antibodies in 20 of the patients in enzyme-linked immunosorbent assay.

RESULTS

The overall prevalence of eye signs in patients with Hashimoto's thyroiditis was 34%, of whom about a quarter had chronic UER, determined as a margin-reflex distance of >5 mm, as the main sign. There was no correlation between eye signs and cigarette smoking. Overall, there was only a modest correlation between eye signs and positive antibody tests, and 40% of patients with no eye signs at the time of study were antibody positive.

CONCLUSION

Eye changes, in particular UER, are common in patients with Hashimoto's thyroiditis. Since thyroid stimulating hormone-receptor antibodies are not usually associated with Hashimoto's thyroiditis, autoimmune mediated damage of the levator palpebrae superioris (eyelid) muscle cannot be due to these antibodies. Although eyelid abnormalities may be a minor problem for most patients, for some there are major cosmetic implications requiring surgical management.

Update on thyroid eye disease and management

Thyroid eye disease is a heterogeneous autoimmune orbital reaction typically manifesting in middle age. The inflammation may parallel or remain isolated from a related inflammatory cascade in the thyroid called Graves' disease. The orbital manifestations can lead to severe proptosis, dry eyes, strabismus, and optic neuropathy. In this article, we will discuss this unique condition including the ophthalmic findings and management.

Thyroid eye disease

Thyroid eye disease remains one of the most common orbital abnormalities encountered by ophthalmologists. While the maintenance of thyroid function remains of paramount importance to the patient's health, the appearance of the orbit, including the eyelid position and position of the globe, proptosis, remains of paramount importance to the patient. Following stabilization of the condition of the globe in the patient with thyroid eye disease, attention is then focused on the rehabilitation of the thyroid orbit. The etiology, diagnosis, and management of thyroid eye disease are discussed.

Peripheral blood T lymphocyte sensitisation against calsequestrin and flavoprotein in patients with Graves' ophthalmopathy

Thyroid-associated ophthalmopathy (TAO) is an orbital autoimmune disorder of the extraocular and eyelid muscles and surrounding connective and adipose tissue. Although mononuclear cell infiltration of orbital tissue is a characteristic feature of TAO the likely role of T lymphocyte reactivity against eye muscle antigens in the initiation of eye muscle damage in TAO has not been explored in detail. Therefore, we tested for T lymphocyte sensitisation to three eye muscle antigens namely, calsequestrin, G2s and flavoprotein (Fp), in patients with Graves' ophthalmopathy (GO), Graves' hyperthyroidism (GH) without ophthalmopathy and age and sex matched normal subjects. T lymphocyte reactivity was determined in a proliferation assay, results being expressed as stimulation index (SI). Mean ( +/- SE) SI for patients with GO, but not GH without ophthalmopathy, were significantly greater than that for normal subjects for calsequestrin and Fp, but not G2s. Mean ( +/- SE) SI was also significantly increased in patients with active ophthalmopathy, but not chronic ophthalmopathy, compared to normal subjects, for calsequestrin and Fp, but not G2s. Overall, positive lymphocyte proliferation to calsequestrin was demonstrated in 59% of patients with GO and 33% of patients with GH, which was significantly greater than in normals for both groups. In conclusion, we have demonstrated significant T lymphocyte reactivity to calsequestrin and, to a lesser extent, Fp in patients with GO. Because calsequestrin is located in the cell membranes of the eye muscle cell during the myotubular stage of the cell cycle, its targeting might be the primary reaction which leads to extraocular muscle inflammation in patients with GH.

Antibodies against calsequestrin and type XIII collagen are good markers for chronic upper eyelid retraction

PURPOSE

Chronic upper eyelid retraction is a common manifestation of thyroid-associated ophthalmopathy (TAO) but can occur as a dominant feature of ophthalmopathy in patients with Graves' hyperthyroidism and in association with Hashimoto's thyroiditis in the absence of other eye signs except mild proptosis.

METHODS

We measured antibodies against calsequestrin, flavoprotein (Fp), G2s, and collagen XIII in an enzyme-linked immunosorbent assay (ELISA) in 15 patients with chronic upper eyelid retraction.

RESULTS

Calsequestrin antibodies were detected in 67% of patients with upper eyelid retraction, Fp antibodies in 47%, G2s antibodies in 20%, and collagen XIII antibodies were detected in 40% of these patients at the first visit. These prevalences were significantly greater than normal for calsequestrin and collagen XIII, but not for Fp and G2s antibodies. On follow-up, calsequestrin antibodies were detected in two more patients, for an overall prevalence of 80%. Levels of the four antibodies remained fairly constant over the study period and generally correlated with the presence and severity of upper eyelid signs.

CONCLUSIONS

These findings support the notion that autoimmune attack against calsequestrin and collagen XIII in the levator palpebrae superioris (LPS) muscle may play a role in the pathogenesis of upper eyelid retraction and that lid retraction may be the dominant feature of ophthalmopathy in patients with Hashimoto's thyroiditis and non-autoimmune thyroid disease. Because calsequestrin is an intracellular protein, the corresponding autoantibodies probably do not initiate LPS muscle inflammation but may contribute to its damage. The mix of antibodies against calsequestrin and collagen XIII may shed light on the diverse presentations found in thyroid-associated ophthalmopathy.

Susceptibility genes in Graves' ophthalmopathy: searching for a needle in a haystack?

The variety of clinical presentations of eye changes in patients with Graves' disease suggests that complex interactions between genetic, environmental, endogenous and local factors influence the development/severity of Graves' ophthalmopathy (GO). At present, the role of genetic factors in the development of GO remains unknown. Based on small case-control association studies with candidate genes, several susceptibility loci in GO have been proposed. These are human leucocyte antigen (HLA, 6p21.3), cytotoxic T-lymphocyte antigen-4 (CTLA-4, 2q33), tumour necrosis factor (TNF, 6p21.3), interferon-gamma (IFN-gamma, 12q14), intercellular adhesion molecule-1 (ICAM-1, 19p13), and thyroid stimulating hormone receptor gene (TSH-R, 14q31). Unfortunately, these results were either not confirmed or require replication in larger studies. There are many reasons for the lack of reproducibility of association studies in GO, including poor characterization of the studied groups and small sample sizes, which may result in both false positive and negative results. Thus, the genetic background of GO remains to be elucidated in future research. However, the possibility that GO may be a genetically heterogeneous disorder, or that the development of GO may be predominantly influenced by environmental factors such as cigarette smoking, can not be disregarded.

Study of serum antibodies against three eye muscle antigens and the connective tissue antigen collagen XIII in patients with Graves' disease with and without ophthalmopathy: correlation with clinical features

OBJECTIVE

The extraocular muscles are one of the primary tissues implicated in the autoimmune-mediated inflammation of thyroid-associated ophthalmopathy (TAO). Our aim was to determine the prevalence and level of antibodies against three candidate eye muscle antigens and the orbital fibroblast membrane antigen collagen XIII, in well-characterized patient groups.

STUDY DESIGN AND PATIENTS

The study cohort consisted of patients with Graves' hyperthyroidism with and without ophthalmopathy, controls patients with other thyroid or other autoimmune disorders and healthy subjects. The presence of eye muscle antibodies was determined using an optimized and standardized enzyme-linked immunosorbent assay. We measured antibodies against (i) the 67-kDa flavoprotein (Fp) subunit of the mitochondrial enzyme succinate dehydrogenase; (ii) G2s, a 141 amino acid fragment of the winged-helix transcription factor FOXP1; (iii) calsequestrin, a 63-kDa calcium-binding protein; and (iv) collagen XIII, a connective tissue protein that is closely linked to the congestive ophthalmopathy subtype of TAO. Eye muscle antibody levels were correlated with clinical diagnosis and presence or not of ophthalmopathy.

RESULTS

Prevalences of positive antibody tests to calsequestrin (75.0%) and collagen XIII (43.8%) were significantly greater in Graves' disease (GD) patients with ophthalmopathy than in healthy subjects, whereas modest significance was demonstrated with antibodies against Fp, but not G2s. Significantly greater serum levels of antibodies against calsequestrin, G2s, and collagen XIII, but not Fp, were found in GD patients with ophthalmopathy compared to control patients without eye disease and healthy subjects.

CONCLUSIONS

Calsequestrin and collagen XIII antibodies are the most specific to TAO, whereas antibodies against G2s, and to a lesser extent Fp, are also markers of ophthalmopathy, but less reliable. These results are unique in that it is the first time the significance of a panel of three candidate eye muscle antibodies and a connective tissue antibody have been evaluated in the same patients with ophthalmopathy.

Antibodies targeting the calcium binding skeletal muscle protein calsequestrin are specific markers of ophthalmopathy and sensitive indicators of ocular myopathy in patients with Graves' disease

We have identified several eye muscle antigens and studied the significance of the corresponding serum autoantibodies in patients with Graves' disease. Of these antigens, only calsequestrin is expressed more in eye muscle than other skeletal muscles, which could explain at least partly the specific involvement of eye muscle in patients with Graves' disease. Earlier, we found a modest relationship between anti-calsequestrin antibodies and ophthalmopathy, but in that study we used calsequestrin prepared from rabbit heart muscle and measured antibodies by immunoblotting. We have reinvestigated the prevalences of anti-calsequestrin antibodies in larger groups of well-characterized patients with thyroid autoimmunity with and without ophthalmopathy and control patients and healthy subjects, using standard enzyme-linked immunosorbent assay incorporating highly purified rabbit skeletal muscle calsequestrin, which has a 97% homology with human calsequestrin, as antigen. Anti-calsequestrin antibodies were detected in 78% of patients with active congestive ophthalmopathy, in 92% of those with active inflammation and eye muscle involvement, but in only 22% of patients with chronic, 'burnt out' disease. Tests were also positive in 5% of patients with Graves' hyperthyroidism without evident ophthalmopathy (two patients) and one patient with 'watery eyes' but no other clear signs of congestive ophthalmopathy and IgA nephropathy and no known thyroid disease, but in no patient with Hashimoto's thyroiditis, toxic nodular goitre, non-toxic multi-nodular goitre or diabetes, or age- and sex-matched healthy subjects. In serial studies of all 11 patients with Graves' hyperthyroidism who had active ophthalmopathy at the time of the first clinic visit, or developed eye signs during the first 6 months, and positive anti-calsequestrin antibodies in at least one sample, anti-calsequestrin antibodies correlated with the onset of ocular myopathy in six patients. Antibodies targeting calsequestrin appear to be specific markers for ophthalmopathy and sensitive indicators of the ocular myopathy subtype of ophthalmopathy in patients with thyroid autoimmunity. However, these results must be considered preliminary until a large prospective study of patients with newly diagnosed Graves' hyperthyroidism, in which serum levels of calsequestrin antibodies are correlated with clinical changes and orbital eye muscle and connective tissue/fat volumes, has been carried out.

Pharmacological Treatments for Thyroid Eye Disease

Thyroid eye disease (TED), which affects the majority of patients with Grave's disease, is associated with significant ophthalmic morbidity. In patients with mild disease, supportive treatment with lubricating medication can be sufficient. However, in patients with severe TED and disfiguring proptosis or sight-threatening neuropathy, more aggressive medical or surgical interventions are necessary. Corticosteroids remain the preferred pharmacological treatment modality in the majority of patients with an active inflammatory component. Other immunosuppressive drugs in combination with corticosteroids may be helpful in patients with corticosteroid-resistant TED. Newer agents such as somatostatin analogues have not shown to be of significant clinical benefit; however, initial studies on the use of antioxidants and cytokine antagonists are encouraging.

Serum antibodies to collagen XIII: a further good marker of active Graves' ophthalmopathy

OBJECTIVE

In Graves' ophthalmopathy (GO) intercellular adhesion molecule-1 (ICAM-1) is thought to play a key role in lymphocyte infiltration into the orbit, and serum levels of its soluble form are positively correlated to clinical activity score (CAS). Serum antibodies against collagen XIII (CollXIIIAb), a plasma membrane protein expressed at a low level in almost all connective tissue-producing cells, have been detected in GO, but their significance is unclear. The aim of this study was to search for CollXIIIAb in Graves' patients with and without ophthalmopathy and to correlate their levels with CAS and with serum soluble ICAM-1 (sICAM-1) values.

PATIENTS

We studied 66 patients with Graves' disease whose sera had been previously tested for sICAM-1 levels, grouped as follows: 28 with moderate and active ophthalmopathy (group 1), 12 of them hyperthyroid (group 1a) and 16 euthyroid (group 1b); 13 with mild and inactive ophthalmopathy and normal thyroid function (group 2); 25 without ophthalmopathy (group 3), 11 of them hyperthyroid (group 3a) and 14 euthyroid (group 3b). Finally, 26 sera of normal controls were studied.

MEASUREMENTS

CollXIIIAb were evaluated by an enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

In group 1 patients, CollXIIIAb were detected at high levels in 8/12 (66.6%) in group 1a [optical density (OD) ranging from 0.529 to 0.894] and in 10/16 (62.5%) in group 1b (OD 0.560-0.855). In group 2 patients, CollXIIIAb were detected but at low levels (OD 0.205-0.260) in 4/13 patients (30.7%). In group 3 patients, CollXIIIAb were present at low levels in 6/11 (54.5%) of group 3a and in 5/14 (35.7%) of group 3b (OD 0.215-0.290 and 0.144-0.245, respectively). CollXIIIAb were detected in only 4/26 normal controls (15%) but at low levels (OD 0.150-0.185). CollXIIIAb values in both groups 1a and 1b were significantly higher than those of the remaining groups. A positive correlation between CollXIIIAb levels and CAS but not thyroid hormone levels was found in groups 1a, 1b and 2. Moreover, a positive correlation between CollXIIIAb levels and sICAM-1-values was also evidenced in all three groups.

CONCLUSIONS

Our results suggest that CollXIIIAb could be considered as a further good marker of active inflammatory processes involving the adipose connective tissue in GO. In particular, the high levels of CollXIIIAb in sera of Graves' patients with active ophthalmopathy could reflect an increased expression of type XIII collagen on the membrane of activated fibroblasts in these patients. Thus, the evaluation of these antibodies could be added to other known markers as a useful and inexpensive tool in monitoring Graves' patients and in modulating the treatment of GO.

Thyroid-associated ophthalmopathy: a practical guide to classification, natural history and management

Thyroid-associated ophthalmopathy (TAO) is an autoimmune disorder that can be divided into three clinical subtypes: congestive, myopathic and mixed ophthalmopathy. It is probably caused by immune cross-reactivity between orbital and thyroid antigens. The best candidate antigens are the thyrotropin receptor and the novel protein, G2s, which is now identified as a fragment of the winged helix transcription factor, FOXP1. The relationship between radioiodine therapy and TAO is controversial, with two randomised controlled trials showing a transient worsening of the eye disease after treatment. The diagnosis of TAO is a clinical one, based on the presence of specific symptoms and signs. Orbital imaging, preferably magnetic resonance imaging, is useful when the diagnosis is in doubt and in patients with suspected optic neuropathy who may benefit from early intervention. Despite their lack of specificity, orbital antibodies may add weight to the diagnosis and may potentially be a useful tool in classifying the different subtypes of TAO and in monitoring disease activity. While antibodies against G2s and the thyrotropin receptor are seen in all subtypes, those against Fp and collagen XIII may be associated with the myopathic and congestive subtypes, respectively, where Fp is the flavoprotein subunit of the mitochondrial enzyme, succinate dehydrogenase. In most patients, TAO is self-limiting and no specific treatment is required. When treatment is indicated, glucocorticoids are the mainstay of therapy. Orbital radiotherapy improves the efficacy of glucocorticoids, but is probably less beneficial as monotherapy. Orbital surgery is best reserved for patients with 'burnt out' inactive disease, but urgent orbital decompression may be required for optic neuropathy. The severity and clinical activity of TAO are important in determining the need for specific treatment and the likelihood of success with medical therapy, respectively.

Eye muscle antibodies in Graves' ophthalmopathy: pathogenic or secondary epiphenomenon?

The extra ocular (eye) muscles are one of the principal tissues involved in the autoimmune-mediated inflammation of Graves' ophthalmopathy (GO). Several eye muscle proteins are targeted by autoantibodies or sensitized T lymphocytes, or both, and include: G2s, which is now identified as the terminal 141 amino acids of the winged-helix transcription factor FOXP1, the flavoprotein (Fp) subunit of the mitochondrial enzyme succinate dehydrogenase, the so-called "64kDa protein", a non-tissue specific membrane protein called 1D and the calcium binding protein calsequestrin. Of these, antibodies against G2s and Fp are the most sensitive markers of eye muscle damage in patients with thyroid autoimmunity even though neither antigen is specific to eye muscle and neither antibody is specific to GO. However, the recent finding that the calsequestrin gene is 4.7 times more expressed in eye muscles than other skeletal muscles suggests that we should reconsider the possible role of anti-calsequestrin autoantibodies in ophthalmopathy. GO may comprise two main subtypes with different pathogenetic mechanisms, namely ocular myopathy in which eye muscle inflammation predominates and congestive ophthalmopathy where inflammatory changes occur in the periorbital connective tissues in the absence of eye muscle dysfunction. Anti-G2s and anti-Fp antibodies are closely associated with the ocular myopathy subtype of GO while antibodies targeting type XIII collagen, the only member of the collagen family to have a transmembrane domain, are closely linked to congestive ophthalmopathy. Since both G2s and Fp are intracellular antigens it is unlikely that either antibody causes eye muscle fiber damage in GO, although a role in the later stages of the disease when the fiber has released its cellular contents has not been excluded. Eye muscle antibodies that are cytotoxic to eye muscle cells in antibody-dependent cell-mediated cytotoxicity (ADCC) are more likely to play a role in eye muscle fiber damage since they target a putative eye muscle cell membrane antigen, the identity of which is currently being investigated. While anti-G2s and anti-Fp antibodies are probably secondary to an underlying reaction, such as cytotoxic T lymphocyte targeting of an eye muscle membrane antigen that has yet to be identified, they are reliable markers of immunologically mediated eye muscle fiber damage in patients with Graves' hyperthyroidism. In conclusion, while a pathogenic role for eye muscle antibodies has not been excluded, they are most likely secondary to cytotoxic T cell reactions in GO and, as such, good markers of this autoimmune disease.

Susceptibility of Ocular Tissues to Autoimmune Diseases

The orbital tissues may form a unique immunological environment, as evidenced by autoimmune disorders that specifically target orbital tissues, particularly myasthenia gravis (MG) and Graves' ophthalmopathy (GO). The reasons for the preferential susceptibility are likely to be multiple, based on the interplay of molecular and physiological properties of extraocular muscles (EOM), the unique requirements of the ocular motor system, and the specific autoimmune pathology. Of general importance, even a minor loss of EOM force generation will sufficiently misalign the visual axes to produce dramatic symptoms, and proprioceptive feedback is limited to overcome such a deficit. Particular to MG, EOM synapses appear susceptible to neuromuscular blockade, the autoimmune pathology differs between ocular and generalized MG patients, and the influence of complement regulatory factors may be less prominent in preventing damage at EOM neuromuscular junctions. GO pathogenesis is poorly understood, but shared epitopes of orbital fibroblasts, EOM, and thyroid could lead to specific autoimmune targeting of these tissues. The differential response of orbital fibroblasts to cytokines may be a key factor in disease development. Greater appreciation of the immunologic environment of orbital tissues may lead to therapies specifically designed for orbital autoimmune diseases.

Differential susceptibility of the ocular motor system to disease

This review summarizes an alternative approach to the understanding of neuromuscular disease. By contrasting disease susceptibility of extraocular muscle and ocular motor neurons, it is hoped that unique insights into disease mechanisms may be identified. Disorder of eye movements leads to dramatic symptoms for patients and the ocular motor system is relatively limited in its ability to compensate rapidly for such disruptions. However, more profound reasons exist as to why myasthenia gravis compromises neuromuscular transmission at ocular muscle synapses as well as why Graves' ophthalmopathy exists. In contrast, muscular dystrophies spare the eye muscles while devastating all other skeletal muscles; the same is true for motor neuron diseases. It is hoped that this review will encourage others to view the world of neuromuscular diseases as delineated into those that spare the ocular motor system and those that do not.

Eye muscle antibodies and subtype of thyroid-associated ophthalmopathy

The eye changes associated with Graves' hyperthyroidism can be classified into two subtypes, congestive ophthalmopathy (CO), in which inflammatory changes in the periorbital tissues predominate, and ocular myopathy (OM), in which eye muscle damage is the main feature. Antibodies against the flavoprotein (Fp) subunit of succinate dehydrogenase (SDH), the 64-kd protein, and G2s, a thyroid and eye muscle shared protein of unknown function, are good markers of eye muscle cell damage in patients with OM. Another antigen associated with ophthalmopathy is the flavine adenine nucleotide (FAD) cofactor of several mitochondrial enzymes, including SDH. We tested for serum antibodies against purified human recombinant Fp, FAD, and a G2s fusion protein, in patients with thyroid-associated ophthalmopathy (TAO) and control patients and subjects, in enzyme-linked immunosorbent assay. Antibodies against Fp were detected in 32% of patients with TAO, 30% with Graves' hyperthyroidism (GH), 16% with Hashimoto's thyroiditis (HT), in 14% of patients with multi-nodular goiter (MNG), and in 6% of normal subjects. Antibodies against FAD were found in 24%, 30%, 24%, and 14%, respectively, of these patients and in 12% of the normals, while antibodies against G2s were detected in 50% of patients with TAO, 40% with GH, 40% with HT, in 29% of patients with MNG, and in 7% of normals. We also tested for antibodies against SDH, FAD, and G2s in 12 patients with GH who developed CO (6 patients) or OM (6 patients) after treatment with antithyroid drugs. Of the 6 patients who developed OM, antibodies against SDH preceded the onset of eye disease in 4 and coincided with it in 2, antibodies against G2s preceded eye muscle disease in 5 and coincided with it in 1 patient while antibodies against FAD preceded the development of OM in 5 patients. Of the 6 patients who developed CO, antibodies against SDH were detected in only one patient and borderline levels were demonstrated in 1, while anti-FAD and anti-G2s each preceded the onset of eye signs in 6 patients. Positive sera from another group of patients with TAO, and a second group of normal subjects, were tested at increasing serum dilutions. Sera from the two groups showed similar dilution patterns, except for a few patients with TAO in whom increasing dilutions was associated with increased, then decreased, antibody levels. In this experiment the prevalences of the two antibodies were much greater in patients with TAO namely, 67% for anti-Fp and 89% for anti-G2s, while the prevalences in the normals were 11% and 22%, respectively. The reason for this apparent discrepancy is not clear but may reflect subject and assay differences. Because Fp is found within the mitochondrial membrane it is likely that the corresponding antibodies are produced after eye muscle necrosis, and do not play a role in its pathogenesis. The primary reaction in the eye muscle may be T-cell autoimmunity against G2s, although this has not been proven. The mechanism for the production of antibodies against G2s, FAD, and Fp in subjects who do not have ophthalmopathy is unclear. The significance of such antibodies in control subjects is presently being addressed in our laboratory.