Best Disease is a Phenocopy of North Carolina Macular Dystrophy (NCMD / MCDR1)

Abstract

Purpose : North Carolina Macular Dystrophy (NCMD / MCDR1) and Best disease are both autosomal dominant macular dystrophies. While both have phenotypic variability, NCMD has considerably more. NCMD has three grades of severity which are present from birth. NCMD grade 1 is drusen, grade 2 is confluent drusen and / or small fibrosis and CNVM, grade 3 is a developmental defect (coloboma like) in the central macula. Isolated individuals outside the context of other affected family members can be difficult to accurately diagnose and differentiate the two disease intities. We will perform a case series evaluation of the similarities and differences between Best disease and NCMD grade 2.

Methods : Clinical findings including fundus photography and OCTs were evaluated in 5 individuals with NCMD grade 2 and two with Best disease. EOG was performed in one NCMD subject. Sanger DNA sequencing was performed to confirm diagnoses. IRB approval was obtained.

Results : Five of NCMD grade 2 individuals have clinical findings indistinguishable from Best's macular dystrophy. One NCMD subject had an abnormal EOG with a normal ERG, which has previously been considered a unique feature of NCMD. OCT in Best disease can demonstrate a lucency deep to the elevated vitelliform lesion which is not seen in NCMD. One NCMD grade 2 subject had had elevated submacular fluid giving a pseudo-vitelliform appareance on OCT.

Conclusions : Best disease is another phenocopy of NCMD. There is considerable clincial overlap between NCMD and Best macualr dystrophy. Like Best disease, NCMD can also have a normal EOG with a normal ERG. Examining other family members can help differentiate the two. DNA sequencing can provide a more definitivve molecular diagnosis.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.