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Dr. Balamurugan Sivaraman
Aravind Eye Hospital, Puducherry - 605 007
India

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Multiple Evanescent White Dot Syndrome (MEWDS) was first described by Jampol.L.M and colleagues.[1] Due to the resemblance to various clinical entities, it has been included in White Dot Syndrome by those who coined this term. MEWDS occurs in young healthy myopic females. The common signs include unilateral decrease in vision associated with paracentral scotoma. Lesions usually affect the posterior pole and involve the outer retina and retinal pigment epithelium.

However, in the recent years, atypical presentation has been described, which includes bilaterality and recurrence of the disease in 14% of patients.[2] Bilaterality of the disease includes simultaneous or sequential involvement of the eye in 10% of the patient.[2],[3] Although overlap of the disease with other entities of white dot syndrome occurs, patient's symptoms should be considered. Though the exact pathogenesis of disease remains unknown, a viral flu-like prodrome with immune-mediated mechanism and genetic susceptibility is suspected. In all presentation of MEWDS, a predeliction exists in the peripapillary region. The ciliary arteries communicate with the retinal arteries and are involved with the enlargement of the blind spot, which is characteristically seen in all presentations of this disorder.[4]

The methodology used for the diagnosing this clinical entity in the past was based on the observation of signs. With the advent of Optical Coherence Tomography, a definite loss of the outer retinal layer due to inflammation of the photoreceptors was characteristic of MEWDS.[3]

José Ignacio Vela et al.[5] have reported an unusual presentation of MEWDS with confluent circumpapillary retinal white spot without optic nerve swelling or foveal granularity, which represents an unusual presentation of MEWDS at 3 days after the onset of symptoms. This early stage is probably missed in most cases due to the mild symptoms and delay in referral. Moreover, multimodal imaging is often scheduled a few days later.

Similarly Cahuzac et al.[6] reported four patients within 1 week of onset. They reported that ellipsoid zone disruption starts simultaneously around the optic nerve and in a very restricted submacular area before extending diffusely. They called this early stage “hyper-early” MEWDS. However, white spots were noted in the three cases, and foveal granularity was found in all of them. Ray and Loewenstein have also reported a large white peripapillary outer retinal lesion that evolved into a more classical MEWDS appearance of the fundus.[7] However, Jampol et al.[8] have said that these geographic lesions may represent a confluence of more typical MEWDS spots.

Luttrull et al.[9] have described a morphological variant of multiple evanescent white syndrome. They have concluded that progressive geographic circumpapillary discoloration, appearing as a giant white spot, occurs rarely in severe cases of multiple evanescent white-dot syndrome. This appearance may suggest a disorder other than multiple evanescent white-dot syndrome.

Shelsta et al.[3] described three unusual cases with classic complaints of MEWDS. These three patients had foveal involvement without white spots. They also had the classic foveal granularity and mild optic disc swelling and/or peripapillary whitening. The characteristic hyperfluorescent lesions were not seen on fluorescein angiography, and indocyanine green imaging did not demonstrate typical feature of hypofluorescence or leakage. However, optical coherence tomography showed focal disruption or loss of the inner segment-outer segment photoreceptor line in all cases.

Peripapillary loss of outer retinal layer on SD-OCT can be an initial manifestation of MEWDS. Hence, ophthalmologists should be aware of this early stage of MEWDS to avoid initial misdiagnosis.

Therefore, multimodal imaging of the retina in patients with MEWDS shows features that may help in the diagnosis of the disease. MEWDS is predominantly not only a disease of the outer retina, centered at the ellipsoid zone, but also involves the interdigitation zone and the outer nuclear layer.

MEWDS can masquerade other clinical entities. A suspicion of infectious, inflammatory, and neoplastic entities should be considered.[10] Acute idiopathic blind spot enlargement syndrome can mimic MEWDS with mild disc edema, without white dots.[3]

The authors have reported centrifugal propagation of the circumpapillary lesion in MEWDS and have postulated that sequential sublethal infection of photoreceptors and spread to the nearby cells may be an alternative possible pathological mechanism.[11]

Characteristic white dots may not be present at onset in MEWDS. Ancillary investigations will be beneficial to the clinician. Suttle clinical signs and symptoms should be considered with due value in the early diagnosis of MEWDS.

References