Galactosialidosis Type IIb with Bilateral Macular Cherry-Red Spots but Mild Dysfunction

Galactosialidosis is a rare metabolic disorder resulting from mutations in the CTSA gene. Few studies have reported on the ocular findings of galactosialidosis type IIb in detail. We report on a case of galactosialidosis, the diagnosis of which was suggested by bilateral macular cherry-red spots, which is an indication of lysosomal storage disease. In this case, retinal and systemic dysfunctions were mild. Genetic studies revealed an abnormality of relevant protective proteins, and thus a definitive diagnosis was made. The patient was a 35-year-old man who had blurred vision from young age, but he did not seek any therapy due to good visual acuity. He visited a local clinic after the blurred vision in the left eye worsened and was referred to us for bilateral macular cherry-red spots. He had no family history of note. We observed fine grayish-white deposits in the corneal stroma and fine opacity of the lens. Optical coherence tomography showed a hyperreflective region and a thick bilateral retinal ganglion cell layer. Goldmann perimetry showed focal loss of sensitivity. There was almost no functional decline noted on multifocal electroretinography. Lysosomal storage disease was suspected due to corneal clouding and macular cherry-red spots, and so further evaluation was performed. Though neurological abnormality was mild, we made a diagnosis of galactosialidosis because of decreased activity of β-galactosidase and sialidase. Genetic studies revealed an abnormality of relevant protective proteins. Since the onset was later in life and clinical symptoms were mild, we expect that the ophthalmological findings will remain stable. Long-term observation is necessary for this case.