Later-onset fabry disease: An adult variant presenting with the cramp-fasciculation syndrome

Background: Classic Fabry disease, an X-linked recessive lysosomal storage disease due to the deficient activity of α-galactosidase A, typically presents in early childhood with acroparesthesias, angiokeratomas, hypohidrosis, and corneal dystrophy. The neuropathic pain presumably results from glycosphingolipid accumulation in the vascular endothelium and in small-caliber nerve fibers, and is treatable by enzyme replacement therapy. Later-onset variants with residual α-galactosidase A activity lack vascular endothelial involvement and classic symptoms, which lead to the development of cardiac and/or renal disease after the fourth decade of life. Objective: To expand the later-onset Fabry phenotype to include cramp-fasciculation syndrome without small-fiber neuropathy. Methods: A 34-year-old man who presented with chronic exercise-induced pain, fasciculations, and cramps of the feet and legs, and his similarly affected mother, were evaluated. Clinical, biochemical, and molecular studies were performed. Results: Clinical evaluation suggested the diagnosis of Fabry disease, which was confirmed by reduced plasma and leukocyte α-galactosidase A activities (8.8% and 13.4% of normal, respectively) due to a missense A143T mutation. His mother was heterozygous for the A143T mutation. Conclusion: The presentation of cramps and fasciculations without apparent small-fiber neuropathy expands the phenotype of later-onset Fabry disease.