Novel Method Detects Intraocular Lymphoma

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A study by investigators at the Proctor Foundation and the University of California San Francisco (UCSF) shows that metagenomic deep sequenc­ing (MDS) holds promise as a future diagnostic tool for uveitic masquer­aders, including primary vitreoretinal lymphoma (PVRL).¹

“The gold standard for diagnosing PVRL is by identifying lymphomatous cells classically via cytopathology,” said lead author John Gonzales, MD, at Proctor. “Other ancillary tests include flow cytometry, IgH gene rearrange­ment, and a newer test that identifies a common mutation in the MYD88 gene.”

“In this study, we described 2 patients with presumed infectious uveitis, [who were] later determined to have intraoc­ular lymphoma by MDS and confirmed with conventional diagnostics,” said co­author Thuy Doan, MD, PhD, at UCSF.

How does MDS work? MDS is a high-throughput sequencing approach that can interrogate all of the genomic information in a clinical sample. “We theoretically can pick up any mutations a patient has, in addition to any non­host genomes, such as bacteria and viruses,” Dr. Doan said. “MDS is so sensitive, we can use as little as 20 to 50 microliters of intraocular fluid, and this amount can be obtained routinely with an anterior chamber paracentesis performed in the clinic.”

Surprising results. Drs. Doan and Gonzales outlined the study patients and results:

Patient 1 had B-cell vitreal lympho­ma. Routine testing with pathogen-directed PCR analysis of ocular fluid after paracentesis was negative for her­pes simplex virus (HSV), varicella zos­ter virus (VZV), and cytomegalovirus (CMV). MDS found both Epstein-Barr virus and human herpesvirus 8 present in the patient sample. Coinfection with these viruses is known to drive lymph­oproliferation.

Patient 2 had intraocular B-cell lymphoma. Routine testing with pathogen-directed PCR was negative for HSV, VZV, CMV, and Toxoplasma gondii. Cytopathology revealed large B-cell lymphoma. MDS confirmed the negative findings for infection but found a less common, known mutation in the MYD88 gene associated with lymphomas. This patient also had more than 100 other mutations associated with lymphoproliferative disorders, also detected by MDS.

“What’s interesting is that this patient didn’t have the most common MYD88 gene mutation, L265P,” said Dr. Doan. “We found a different MYD88 muta­tion associated with lymphoma, which would have been missed with routine PCR testing.”

Diagnosis is critical, said Dr. Gonza­les, because PVRL has poor outcomes and life expectancy. Both coauthors hope to see MDS in clinical use in 3 to 5 years. “We’re cautiously optimistic and think this has tremendous poten­tial,” said Dr. Doan.

—Rebecca Taylor

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1 Gonzales J et al. Br J Ophthalmol. 2018;102(1):6-8.

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Relevant financial disclosures: Dr. Doan—NEI: S; Research to Prevent Blindness: S; Silicon Valley Community/Huang Pacific Foundation: S; UCSF Resource Allocation Program: S. Dr. Gonzales—NEI: S.

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