NAION and GPA (Granulomatosis with Polyangiitis): An In-Depth Look

Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis, is a rare autoimmune disease characterized by inflammation of small and medium-sized blood vessels (vasculitis). This inflammation can restrict blood flow to vital organs, leading to damage. While GPA can affect any organ, it most commonly involves the sinuses, nose, trachea (windpipe), lungs, and kidneys. Ocular involvement can occur in up to 40% of patients with GPA. This article discusses the connection between Non-arteritic anterior ischemic optic neuropathy (NAION) and GPA.

Understanding Granulomatosis with Polyangiitis (GPA)

Granulomatosis with polyangiitis (GPA) is an uncommon and unexplained autoimmune disease that mainly involves the arterioles, veins, and capillaries. Its pathology is characterized by inflammation of the vascular wall. GPA slows blood flow to some organs. The affected tissues can develop inflamed areas called granulomas. Granulomas can destroy healthy tissue. The exact cause of GPA is unknown, but the immune system may play a role. Some white blood cells may not function as they should, and they may be involved in the disease. The condition can lead to inflamed, narrowed blood vessels and harmful, inflamed tissue masses called granulomas. GPA doesn't spread from person to person. Men and women are equally affected. It is more common in whites.

Symptoms and Diagnosis

Symptoms of GPA can vary. At first, the symptoms can seem like those of a cold. Other symptoms depend on which organs the disease affects. Early symptoms may feel like a cold or flu and can last for weeks or longer. The most frequently involved tissues of GPA are the upper respiratory tract, lung, kidney, skin, eyeball, orbit, ear, joint, and lymph nodes. Diagnosis can be challenging, especially when ocular lesions are present, as they can be easily missed or misdiagnosed due to similarities with other orbital inflammatory lesions, lymphomas, and tumors. Early treatment is important and can help people live full lives.

Ocular Manifestations of GPA

Ocular involvement ranges from 50% to 60% of GPA, and any area of the eye can be affected, with 15-20% of cases exhibiting granulomatous inflammation. GPA may involve any part of the eye and can include conjunctivitis, helcoma, leucitis, retinal vasculitis, and optic neuropathy. Ophthalmic involvement occurs in up to 40% of patients with granulomatosis with polyangiitis (GPA), usually confined to the anterior segment. Scleritis and episcleritis are the most common manifestations, whereas optic neuropathy is reported in only 3% of patients. If the cause of the orbital granulomatous inflammation is not identified early and treatment delayed, this may lead to serious complications of the eyes, such as loss of vision and removal of the eyeballs.

Imaging Findings in GPA Ophthalmopathy

Previous studies on orbital imaging of GPA have primarily been case reports, and a systematic description is lacking. Although, a few large-sample, clinical studies have been conducted, only clinical data have been reported, and the imaging diagnostic features and pathogenesis of the disease have not been extensively explored. Lacrimal gland enlargement and intraorbital pseudotumor are the common imaging manifestations of GPA, but other imaging manifestations have been identified, such as optic nerve sheath, dural matter enhancement, and extraocular myositis. However, these are also present in some orbital inflammatory and tumorous lesions, such as immunoglobulin G4-related ophthalmic diseases (IgG4-ROD), Graves ophthalmopathy, sarcoidosis, and lymphoma. The imaging manifestations of GPA orbital lesions include enlarged lacrimal glands, granulomatous inflammation, extraocular myositis, and optic perineuritis.

A characteristic imaging feature of the group of patients in this study was that the intraorbital granuloma inflammation was mainly located in the extraconal space. There are three main histological changes in GPA-associated granuloma: parenchymal tissue injury, vasculitis, and granulomatous inflammation. Another characteristic imaging manifestation, which was evident in all patients in this study, was inflammatory infiltration of the pterygopalatine fossa, with the pterygopalatine fossa lesions of the transcranial basal foramen involving the adjacent sinus cavernosus, orbital apex, masticatory muscle space, and other structures being visible. GPA also involves the optic nerve sheath, which is characterized by the thickening and strengthening of the optic nerve sheath due to the involvement of inflammatory cells in the optic nerve sheath. In addition to the ocular and endocranium changes, patients with GPA might often have middle-ear mastoiditis.

NAION (Non-Arteritic Anterior Ischemic Optic Neuropathy)

Non-arteritic anterior ischemic optic neuropathy (NAION) is a common cause of sudden vision loss due to optic nerve damage. While not directly caused by GPA, it is important to understand NAION in the context of discussing optic neuropathies.

Understanding NAION

NAION occurs when blood flow to the optic nerve is disrupted, leading to ischemia (lack of oxygen) and damage. This often results in sudden, painless vision loss, typically affecting one eye. The exact cause of NAION is not fully understood, but several risk factors have been identified.

Risk Factors for NAION

Common risk factors for NAION include:

Age: NAION is more common in people over 50.
Crowded Optic Disc: Individuals with a small optic disc, often described as "disc at risk," are more susceptible.
Vascular Diseases: Conditions like hypertension, diabetes, and high cholesterol can increase the risk.
Sleep Apnea: This condition can lead to reduced oxygen levels during sleep, potentially affecting the optic nerve.
Certain Medications: Some medications, such as amiodarone and phosphodiesterase-5 inhibitors (used for erectile dysfunction), have been linked to NAION.

The Link Between GPA and NAION

While NAION is not a direct symptom of GPA, the systemic vasculitis associated with GPA can potentially affect blood flow to the optic nerve, increasing the risk of ischemic optic neuropathy.

Mechanisms of Optic Nerve Damage in GPA

Vasculitis: The inflammation of blood vessels characteristic of GPA can affect the small vessels supplying the optic nerve, leading to ischemia and damage.
Granulomatous Inflammation: In some cases, granulomatous inflammation in the orbit can compress the optic nerve, causing optic neuropathy.
Optic Perineuritis: GPA involves the optic nerve sheath, which is characterized by the thickening and strengthening of the optic nerve sheath due to the involvement of inflammatory cells in the optic nerve sheath.

Optic Neuropathy as a Manifestation of GPA

Optic neuropathy is reported in only 3% of patients with GPA. Its pathogenesis is usually explained by extension of granulomatous inflammation from the sinus or orbit. Therefore, when it occurs, it is mostly accompanied by strabismus, and the optic nerve is damaged due to compression by granulomatous inflammation. Notably, ocular involvement is the first presentation of GPA in 14% of patients.

Isolated Optic Neuropathy in GPA

Isolated optic nerve damage is unclear in GPA. Although granulomatous inflammation is not evident, the optic nerve can be damaged by compression due to pachymeningitis. Alternatively, it can be ascribed to inflammation spreading from the adjacent sinuses to involve the optic nerves in the orbital apex, optic canal, and intracranial segment. Ischemic optic neuropathy secondary to small vessel vascilitis has been proposed a possible mechanism based on temporal artery biopsy findings of leukocytic infiltration, fibrinoid necrosis and occlusion of the small periadvential vessel (vasa vasorum) in one of the reports. Focal vasculitis may cause ischemia and infarction of the optic nerve and retina to resulting in pallid disc edema. The findings of optic nerve sheath and orbital enhancement on the MRI brain and orbits in our patient supports ischemia from posterior ciliary arteries as a possible mechanism for optic neuropathy. Optic perineuritis seen as enhancement of the optic nerve sheath on MRI orbits are seen in a variety of infectious and inflammatory conditions such as, syphilis, sarcoidosis, giant cell arteritis, and GPA.

Diagnosis of Optic Neuropathy in GPA

When a patient with GPA presents with vision loss, it is crucial to differentiate between NAION and optic neuropathy directly related to GPA.

Diagnostic Tools

Ophthalmological Examination: A thorough eye exam, including visual acuity testing, visual field testing, and fundoscopy, is essential.
Imaging Studies: MRI with contrast can help identify optic nerve inflammation, compression, or structural abnormalities.
Blood Tests: ANCA (antineutrophil cytoplasmic antibodies) testing is crucial for diagnosing and monitoring GPA. Elevated CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate) was found in 56% (9/16) of patients.
Lumbar Puncture: CSF analysis showed abnormal results in most cases (6/7, 86%), including albuminocytologic dissociation (n = 3), increased immunoglobulin G index (n = 3), pleocytosis (n = 2), and a positive oligoclonal band (n = 1).
Biopsy: In some cases, a biopsy of affected tissue may be necessary to confirm the diagnosis of GPA.

Differential Diagnosis

Differentiating between NAION and GPA-related optic neuropathy involves considering:

Systemic Symptoms: GPA often presents with systemic symptoms such as respiratory issues, kidney problems, and joint pain, which are absent in isolated NAION.
ANCA Results: Positive ANCA results strongly suggest GPA.
Imaging Findings: MRI findings suggestive of inflammation or compression of the optic nerve are more indicative of GPA-related optic neuropathy.

Management and Treatment

The management of optic neuropathy in GPA involves treating the underlying systemic disease and addressing the optic nerve damage.

Treatment Strategies

Immunosuppressive Therapy: Corticosteroids and other immunosuppressive drugs like cyclophosphamide, methotrexate, or rituximab are used to control the inflammation associated with GPA.
Anti-VEGF Injections: In some cases, anti-VEGF injections may be used to reduce optic nerve swelling.
Supportive Care: Managing underlying risk factors like hypertension, diabetes, and sleep apnea is crucial.
Low Vision Rehabilitation: Patients with permanent vision loss may benefit from low vision rehabilitation services.

Prognosis

The prognosis for optic neuropathy in GPA depends on the severity of the disease and the promptness of treatment. Early diagnosis and aggressive immunosuppressive therapy can improve visual outcomes.

Visual Outcomes

The final visual outcome was often poor, with significant visual recovery maintained in only eight eyes (8/23, 35%). Recurrence was observed in 10 patients (10/17, 59%) from one to four times, either in the affected eye (n = 9) or fellow eye (n = 4).

Illustrative Cases

Case 1

An 80-year-old female with hypertension and diabetes mellitus presented with an acute decrease in visual acuity in the right eye for 2 days. The patient experienced an unexplained fever and a weight loss of 6 kg in the month prior to presentation. A gadolinium enhancement was found around the right optic nerve sheath on MRI. Multifocal enhancements were documented in the bilateral temporalis, masseter, and pterygoid muscles, aside from maxillary sinusitis and mastoiditis. The serum was positive for cytoplasmic antineurtrophil cytoplasmic antibody (cANCA) and negative for perinuclear ANCA (pANCA). The patient was diagnosed with optic neuropathy associated with GPA. The patient received intravenous methylprednisolone (1 g/day) for five consecutive days. Intravenous rituximab (1,000 mg) was administered for immunomodulation.

Case 2

A 15-year-old male patient with GPA. Cross-sectional T2-weighted imaging showing bilateral enlargement of the lacrimal gland, which exhibited a high signal intensity compared with that of the ectocinerea. Computed tomography (scan of the coronal bone window showing the destruction of the nasal septum and abnormal enhancement of basal cochlea of the patient.

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