A case of congenital myopathy accompanied by tremor due to a MYBPC1 mutation

Expanding the Spectrum of Congenital Myopathy Linked to Variants in the MYBPC1 Gene: A Clinical Report

Objectives

Heterozygous missense variants in MYBPC1 have been recently identified in 13 patients from 6 families with congenital myopathy with tremor. All the patients had mild skeletal myopathy invariably associated with a distinctive myogenic tremor and hypotonia with gradual clinical improvement. However, no phenotypic description has been reported for the neonatal respiratory impairment that patients may suffer.

Methods

We report 3 new patients from 2 independent families with congenital myopathy with tremor.

Results

Tremors and respiratory distress associated with stridor should raise the diagnosis of congenital myopathy with tremors linked to MYBPC1-dominant variants in children with neonatal hypotonia.

Discussion

Neonatal severe respiratory impairment requiring intensive noninvasive ventilation because of stridor is described in 2 patients. Stridor was previously reported in one other case and is part of the clinical features.

Congenital tremor and myopathy secondary to novel MYBPC1 variant

Congenital myopathy with tremor (MYOTREM) is a recently described disorder characterized by mild myopathy and a postural and intention tremor present since early infancy. MYOTREM is associated with pathogenic variants in MYBPC1 which encodes slow myosin-binding protein C, a sarcomere protein with regulatory and structural roles. Here, we describe a family with three generations of variably affected members exhibiting a novel variant in MYBPC1 (c.656 T > C, p.Leu219Pro). Among the unique features of affected family members is the persistence of tremor in sleep. We also present the first muscle magnetic resonance images for this disorder, and report muscle atrophy and fatty infiltration.