Congenital myopathies are typically characterized by the presence of specific structural and histochemical features on muscle biopsy and clinical presentation can include congenital hypotonia, muscle weakness, delayed motor milestones, feeding difficulties, and facial muscle involvement. Serum creatine kinase may be normal or elevated. Heterogeneity in presenting symptoms can occur even amongst affected members of the same family. Congenital myopathies can be divided into three main clinicopathological defined categories: nemaline myopathy, core myopathy and centronuclear myopathy.
Nemaline Myopathy is characterized by weakness, hypotonia and depressed or absent deep tendon reflexes. Weakness is typically proximal, diffuse or selective, with or without facial weakness and the diagnostic hallmark is the presence of distinct rod-like inclusions in the sarcoplasm of skeletal muscle fibers.
Core Myopathy is characterized by areas lacking histochemical oxidative and glycolytic enzymatic activity on histopathological exam. Symptoms include proximal muscle weakness with onset either congenitally or in early childhood. Bulbar and facial weakness may also be present. Patients with core myopathy are typically subclassified as either having central core disease or multiminicore disease.
Centronuclear Myopathy (CNM) is a rare muscle disease associated with non-progressive or slowly progressive muscle weakness that can develop from infancy to adulthood. On muscle histopathology, patients with CNM have increased frequency of central nuclei, as well as type 1 fiber predominance and hypotrophy, in the absence of other significant abnormalities. Other neuromuscular conditions can have similar findings on muscle biopsy, so these features are not always diagnostic for CNM.
Our Congenital Myopathy Deletion/Duplication Panel includes all of the following seventeen genes: ACTA1, CFL2, KBTBD13, NEB, TNNT1, TPM2, TPM3, BIN1, CCDC78, CNTN1, DNM2, MTM1, MYF6, MYH7, RYR1, SEPN1, TTN.