The authors describe the first reported instance of melanoma-associated retinopathy (MAR) positive for antoantibodies to transient receptor potential cation channel, subfamily M, member 1 (TRPM1).
All four previously reported MAR patients with autoantibodies to TRPM1 were Caucasian. The study’s findings suggest that autoantibodies to TRPM1 may play an important role in the pathogenesis of MAR regardless of ethnicity.
An 82-year-old man presented with blurred vision in the right eye and bilateral night blindness and photopsia. Goldmann perimetry revealed a relative central scotoma, including a blind spot in the right eye, as well as a relative scotoma around a blind spot in the left eye. Full-field scoptic electronretinograms (ERGs) showed a “negative-type” pattern bilaterally, suggestive of extensive bipolar cell dysfunction.
Systemic examination subsequently revealed that he had malignant melanoma of the anus with lung metastasis. Malignant melanoma is rare in the Japanese population, with a prevalence of 0.002 percent compared with 0.015 percent in white populations.
Autoantibodies to TRPM1 were detected in the patient’s serum. On the basis of these findings, the patient was diagnosed with MAR likely caused by autoantibodies to TRPM1.
Vitreous opacity developed during follow-up. After oral prednisolone therapy, vitreous opacity and visual symptoms improved.
The patient died as a result of widespread melanoma metastasis 11 months after his initial visit.
The authors say the patient’s “negative-type” ERGs, indicative of extensive bipolar cell dysfunction, led them to suspect that he might have MAR. They therefore recommend that ERGs be performed on patients with progressive visual disturbance of unknown origin.
They conclude that further studies are warranted to determine the proportion of MAR patients who develop TRPM1 antoantibodies, as well as the best treatment option for this type of paraneoplastic retinopathy.