%0 Case Reports
%T Congenital asymmetric distal myopathy with hemifacial weakness caused by a heterozygous large de novo mosaic deletion in nebulin.
%A Sagath L
%A Lehtokari VL
%A Välipakka S
%A Vihola A
%A Gardberg M
%A Hackman P
%A Pelin K
%A Jokela M
%A Kiiski K
%A Udd B
%A Wallgren-Pettersson C
%J Neuromuscul Disord
%V 31
%N 6
%D 06 2021
%M 33933294
%F 3.538
%R 10.1016/j.nmd.2021.03.006
%X We report the first mosaic mutation, a deletion of exons 11-107, identified in the nebulin gene in a Finnish patient presenting with a predominantly distal congenital myopathy and asymmetric muscle weakness. The female patient is ambulant and currently 26 years old. Muscle biopsies showed myopathic features with type 1 fibre predominance, strikingly hypotrophic type 2 fibres and central nuclei, but no nemaline bodies. The deletion was detected in a copy number variation analysis based on next-generation sequencing data. The parents of the patient did not carry the deletion. Mosaicism was detected using a custom, targeted comparative genomic hybridisation array. Expression of the truncated allele, less than half the size of full-length nebulin, was confirmed by Western blotting. The clinical and histological picture resembled that of a family with a slightly smaller deletion, and that in patients with recessively inherited distal forms of nebulin-caused myopathy. Asymmetry, however, was a novel feature.