Anti-CRMP-5 (collapsin response-mediator protein-5) optic neuropathy, also known as anti-CV2 optic neuropathy, is a rare paraneoplastic cause of visual loss, manifesting as prelaminar optic neuritis, uveitis, and/or retinitis.
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Epidemiology
Descriptions of anti-CRMP-5 optic neuropathy are confined to case reports and case series 1-3. Thus, although the incidence is not known, it is likely that anti-CRMP-5 optic neuropathy is very rare. In one large series the median age was 67 years 1, and across multiple series there was a female predominance 1-3.
Associations
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common 1-3
small cell lung cancer (most common)
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rare 1-3
Clinical presentation
The clinical presentation is typically subacute and progressive, often over weeks or months 1-3. Most patients have optic neuropathy in conjunction with either or both of uveitis and retinitis 1-4. Clinical features include 1-4:
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visual loss
typically painless and bilateral
incorporates both reduced visual acuity and/or visual field defects
In addition to ocular manifestations, affected patients may have other neurological paraneoplastic manifestations relating to anti-CRMP-5 or other concurrently present autoantibodies, such as 1-3:
neuropathic disorders: peripheral neuropathy, polyradiculopathy, etc.
cerebellar ataxia
movement disorders: chorea, parkinsonism, myoclonus, etc.
Analysis of cerebrospinal fluid (CSF) typically shows raised protein, and may reveal a lymphocytic pleocytosis 1,2.
Pathology
Anti-CRMP-5 (anti-CV2) is an IgG neuronal intracellular antibody 4. While the CRMP-5 protein is widely expressed throughout the nervous system, including in the optic nerve and retina, it is thought that anti-CRMP-5 is not directly pathogenic in its associated paraneoplastic syndrome 3,4. Instead, it is hypothesized that anti-CRMP-5 plays a role in activating cytotoxic T cells which can then mediate a myriad of neurological manifestations, including optic neuropathy 4, although the exact pathogenesis is yet to be fully elucidated.
Radiographic features
MRI
MRI brain/orbits is typically normal in patients with anti-CRMP-5 optic neuropathy, given the optic neuritis is typically prelaminar and not retrobulbar 1,2. Rarely, there are reports of mild optic nerve enhancement or optic sheath enhancement (optic perineuritis) 3.
Treatment and prognosis
Management across case series is typically with immunosuppression, such as glucocorticoids or intravenous immunoglobulin, and with treatment of the underlying malignancy 1-4. In one large series, immunosuppressive therapy improved ocular symptoms in 50% of patients 1.
Differential diagnosis
other causes of optic neuritis and optic neuropathy
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