Idiopathic orbital myositis is a rare orbital inflammatory disease that primarily affects multiple extraocular muscles, though other non-muscular orbital structures may be affected. The first case was documented in the early 20th century, but isolated muscle cases are very uncommon and were described later.

Due to its low incidence and diverse clinical presentation, it is a challenging entity often misdiagnosed. We present a patient with isolated involvement of the left levator palpebrae muscle, a rare variant of orbital myositis. It can result from a wide variety of etiologies; thus, we propose a diagnostic approach to identify the underlying cause. Finally, since management strategies are not well defined in the literature, we also propose a treatment regimen.

Our diagnostic and management proposal are based on a detailed case study and an extensive bibliographic review. We provide a comprehensive description of the patient´s case, focusing on clinical findings, diagnostic tests, management and outcomes. Written informed consent was obtained from the patient.

For the bibliographic review, Pubmed and Google Scholar were included given their high quality and extensive coverage of scientific articles. A Pubmed search using the terms “levator AND palpebrae AND myositis” yielded 12 articles, 4 of which were selected as the most relevant. Additionally, a search using the terms “levator AND myositis” obtained 27 articles, with 9 selected. Thus, a total of 13 articles were selected. In Google Scholar, “levator” “palpebrae” “myositis” yielded 808 results. After reviewing every abstract, only 95 articles were relevant to our topic. After a comprehensive evaluation, 11 articles were chosen. From the 24 articles reviewed across both platforms, we finally selected 14 to compose the basis of the bibliographic review.

A 23-year-old patient presented to the Emergency Department with a two-week history of mild temporal, periocular and retroocular pain on the left side, accompanied by one week left eyelid ptosis without diplopia. He had no relevant medical history, signs or symptoms of infection, constitutional syndrome or systemic disease, or recent vaccinations or treatments prior to the onset of this disorder. Neurological exam revealed complete and isolated left palpebral ptosis without ophtalmoparesis or pupillary abnormalities (Figure 1(C)).

Figure 1.

Radiological and clinical evolution. (A) The initial MRI, conducted prior to the administration of corticosteroids, revealed intense hyperintensity in the affected area (white arrow). (B) The follow-up MRI, performed five days after initiating treatment, showed a reduction in the previous hyperintensity (white arrow). (C) At the beginning of hospitalization, the patient exhibited complete ptosis. (D) Complete recovery was observed two months after onset.

A comprehensive series of tests were conducted. Blood analysis included erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), creatinine kinase (CK), thyroid function, thyroid antibodies, angiotensin-converting enzyme (ACE), complement, proteinogram, cryoglobulins, and cryocrit, antinuclear antibodies (ANAs), antineutrophil cytoplasmic antibodies (ANCAs), immunoglobulins (Ig)M and IgG anticardiolipin, rheumatoid factor, human leukocyte antigen (HLA)-B27, IgG4, calprotectin, and IgG and IgA anti-transglutaminase. Cerebrospinal fluid (CSF) analysis included cell count, glucose, protein and antiganglioside antibodies. Microbiological tests were performed for syphilis, borrelia, hepatotropic virus, human immunodeficiency virus (HIV), herpes simplex virus (HSV), Epstein-Barr virus (EBV) and Varicella-Zoster virus (VZV) both in blood and CSF. All of them returned normal results. Imaging studies, including ultrasonography of supra-aortic trunks, transcranial doppler ultrasound, brain computed tomography (CT), CT angiography of supra-aortic trunks and chest radiography were all unremarkable. Brain magnetic resonance imaging (MRI) showed T2 FLAIR hyperintensity in the levator palpebrae muscle of the left eye, without abnormal contrast enhancement (Figure 1(A)).

Prednisone treatment was initiated at a dosage of 60 mg/day, followed by a gradual tapering regimen. A follow-up MRI performed 5 days after treatment onset showed a decrease in the previously observed hyperintensity (Figure 1(B)). Patient experienced significant clinical improvement by the time of discharge. Two months after hospitalization, patient fully recovered (Figure 1(D)).

Idiopathic orbital myositis is a rare disease with uncertain origin believed to result from autoimmune mechanisms. It can be associated with: rheumatoid arthritis, ANCA-associated vasculitis, inflammatory bowel disease, systemic or discoid lupus erythematosus, sarcoidosis, giant-cell myocarditis, IgG4-related disease, polychondritis, Behçet disease, psoriasis and psoriatic arthritis, HLA-B27-positive spondylarthritis, Sjögren syndrome, dermatomyositis, scleroderma, undifferentiated connective tissue disease, celiac disease, primary biliary cirrhosis, Kawasaki disease, antiphospholipid syndrome and Nucleotide-binding Oligomerization Domain-2 autoimmune disease. Moreover, certain infections can trigger it, in particular, viral infections of the upper respiratory tract or poststreptococcal pharyngitis. Additionally, drugs or vaccines (checkpoint inhibitors, etanercept, bisphosphonates, statins, interferon α-2β, ribavirin, intravesical Bacillus Calmette-Guérin and influenza vaccine) have also been associated.^{Reference Basilious, Jivraj and DeAngelis1–Reference Sušić, Brajkovic and Kalauz-Surac3}

This condition most frequently occurs in adulthood, particularly in the fourth decade of life and in female patients.^{Reference McNab2–Reference Court and Janicek4} Its course is usually acute or subacute, with frequent spontaneous recovery within six weeks, although symptoms may persist or may recur after previous improvement. In chronic cases, pathological features consist of muscle fibrosis and restrictive myopathy.^{Reference Sušić, Brajkovic and Kalauz-Surac3} The main clinical findings include eyelid edema, ptosis, diplopia and pain that worsens with ocular movements.^{Reference Sušić, Brajkovic and Kalauz-Surac3,Reference Ota, Shimizu and Yoshida5} Medial, lateral, superior, and inferior rectus, and obliques are, in order, the most frequently affected muscles. The levator palpebrae is often affected alongside other muscles, but isolated involvement is extremely rare.^{Reference McNab2,Reference Court and Janicek4}

Given the frequent occurrence of eyelid ptosis in clinical practice, it is essential to consider orbital myositis in the differential diagnosis (Table 1). When a patient presents with palpebral ptosis, the topographic diagnosis can locate the problem at: any point along the course of the third cranial nerve (which innervates the levator palpebrae muscle), from its origin in the midbrain to its entry into the orbit; throughout the path of the sympathetic nervous system fibers (which innervates the Muller’s muscle), from their origin in the posterior hypothalamus to their arrival in the orbit; and even in the muscles themselves responsible for eyelid elevation, inside the orbit. The presence of complete ptosis rules out an involvement of Muller’s muscle and therefore of the sympathetic nervous system and points to a lesion of the levator palpebrae muscle or its innervation by the third cranial nerve. The absence of abnormal pupillary motility and ophthalmoparesis discard a damage to the third cranial nerve. On the other hand, our patient presented periocular pain, which makes it mandatory to consider trigeminal-autonomic headaches in the differential diagnosis since they may be accompanied by palpebral ptosis. However, in such cases, ptosis is not complete as it is due to sympathetic dysfunction. In addition, the pain reported by the patient was persistent over several days and not paroxysmal, which distinguishes his condition from this kind of headaches. All this localizes the problem to the orbit and makes a direct involvement of the levator palpebrae more likely. Finally, the presence of pain and the subacute course compel us to consider the possibility of orbital myositis. In this context, MRI will be crucial for confirming the topographic diagnosis and will help us in the etiological one.^{Reference Ota, Shimizu and Yoshida5–Reference Tung Lai, Leung, Wong, Ho and kwan Chang8}

Table 1.

Summary of primary diagnoses in patients with ptosis and their key differential characteristics

Orbital myositis may result from different conditions, each of them requiring distinct management strategies. Furthermore, it presents multiple differential diagnoses that must be distinguished, as the management approach may differ. Based on an extensive review of the literature, we propose a comprehensive set of diagnostic tests to identify the etiology (Table 2). Physicians should adapt it on a case-by-case basis. For instance, we did not perform collagen profile, lactate/pyruvate or paraneoplastic testing given the absence of clinical, imaging or laboratory suggestive findings. If all diagnostic tests are negative, idiopathic orbital myositis can be assumed, typically with rapid and complete recovery.^{Reference McNab2–Reference Court and Janicek4}

Table 2.

Summary of diagnostic tests for a comprehensive study to identify the underlying cause of orbital myositis and for differential diagnosis ^{Reference McNab2–Reference Ota, Shimizu and Yoshida5,Reference Pidro, Dizdarević, Jovanović, Čerim, Sačak and Miokovic7,Reference Tung Lai, Leung, Wong, Ho and kwan Chang8}

ACE = angiotensin-converting enzyme; ANA = antinuclear antibodies; ANCA = antineutrophil cytoplasmic antibody; CK = creatinine kinase; CRP = C-reactive protein; CT = computed tomography; DNA = deoxyribonucleic acid; EMG = electromyography; ERS = erythrocyte sedimentation rate; HIV = human immunodeficiency virus; HLA = human leukocyte antigen; HSV = herpes simplex virus; Ig = immunoglobulins; IL = interleukin; LRP4 = lipoprotein receptor-related protein 4; MRI = magnetic resonance imaging; MuSK = muscle-specific tyrosine kinase; PET = positron emission tomography; RF = rheumatoid factor; SLE = systemic lupus erythematosus; SSA = anti–Sjögren's-syndrome type A; SSB = anti–Sjögren's-syndrome type B; VDRL = venereal disease research laboratory; VZV = Varicella-Zoster virus.

There is no clear consensus on management. Based on a literature review, we propose an approach as shown in Figure 2. The most common treatment are corticosteroids, specifically prednisone at a dosage of 1–1.5 mg/kg/day, followed by a gradual tapering over 6–12 weeks.^{Reference Ota, Shimizu and Yoshida5} Treatment should ideally begin within the first three weeks of symptom onset, since timing is associated with better outcomes.^{Reference Ota, Shimizu and Yoshida5} One study reported success with a single parabulbar injection of dexamethasone combined with oral corticosteroids and indomethacin.^{Reference Sušić, Brajkovic and Kalauz-Surac3} However, we prefer oral corticosteroids because the latter alternative carries higher risks.

Figure 2.

Flow chart of treatment recommendations. IS = immunosuppressive agents; Iv = intravenous; MPD = metilprednisolone; MTX = methotrexate; PRD = prednisone; TCZ = tocilizumab.

In resistant or recurrent cases, several options can be considered. These include increasing prednisone dose by 5–10 mg/day, switching to intravenous boluses of methylprednisolone, or adding other immunosuppressive agents (methotrexate, azathioprine, mycophenolate, cyclosporine, cyclophosphamide, chlorambucil, rituximab, daclizumab, infliximab and adalimumab). For patients who continue to show inadequate response, tocilizumab, at a dosage of 8 mg/kg/month, may be considered. Tocilizumab has shown positive results in other ocular inflammatory diseases and some reported cases of orbital myositis. It can be administered either alone or in combination with methotrexate. In severe and refractory cases, radiotherapy at doses of 1000–3000 Gy over 2–3 weeks may be used, although this approach comes with significant adverse effects, including dry eye, keratitis, cataract, photophobia, optic neuropathy, radiation retinopathy, etc. Surgery may be necessary in particularly complex cases, performing partial resection for persistent focal masses in diffuse cases or dacryoadenitis. In extreme cases with refractory painful blind eye, ocular exenteration may be considered as a last resort.^{Reference Ota, Shimizu and Yoshida5,Reference Pidro, Dizdarević, Jovanović, Čerim, Sačak and Miokovic7,Reference Meca Casasnovas, Sangrador Pelluz and Sotoca9,Reference Brar, Krishn, Gupta, Prabha, Phutela and Chadha10}

Orbital myositis is a rare disorder that can present in several forms depending on the number and type of structures involved. Isolated levator palpebrae myositis should be considered when a patient presents with subacute periocular pain accompanied by complete ptosis without ophthalmoparesis or pupillary dysfunction.

Given the challenges in diagnosing orbital myositis etiology, we propose a comprehensive series of diagnostic tests which should be adapted case-by-case.

Finally, we recommend a treatment regimen initiating with oral corticosteroids and, when necessary, increasing the dose, switching to intravenous administration, or introducing an additional immunosuppressant. In the most refractory cases, more aggressive treatments such as radiotherapy or surgery may be necessary, weighing the risks.