Progressive cone dystrophy associated with low alpha-L-fucosidase activity in serum and leukocytes.

The enzyme activities of acid phosphatase, beta-glucuronidase, N-acetyl-beta-D-glucosaminidase, and alpha-D-mannosidase were not significantly different in patients with myopia, retinal detachment, hereditary macular dystrophy, and unusual progressive cone dystrophy. alpha-L-Fucosidase activity in sera was lower in three patients with myopia and in two patients with unusual progressive cone dystrophy than in most of the others. Leukocytic alpha-L-fucosidase activity was lower in those with unusual progressive cone dystrophy. The two unrelated patients with unusual progressive cone dystrophy had slowly deteriorating visual acuity, color vision, and photopic electroretinographic responses, but ophthalmoscopically normal fundi and noncontributory family histories.