Nemaline Myopathy 3 (NEM3)

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OMIM®: ⁵⁷ Nemaline myopathy is a form of congenital myopathy characterized by abnormal thread- or rod-like structures in muscle fibers on histologic examination ('nema' is Greek for 'thread'). The clinical phenotype is highly variable, with differing age at onset and severity. Muscle weakness typically involves proximal muscles, with involvement of the facial, bulbar, and respiratory muscles (Ilkovski et al., 2001). Attempts at classification of nemaline myopathies into clinical subtypes have been complicated by the overlap of clinical features and a continuous phenotypic spectrum of disease (North et al., 1997; Wallgren-Pettersson et al., 1999; Ryan et al., 2001; Sanoudou and Beggs, 2001). In general, 2 clinical groups can be readily distinguished: 'typical' and 'severe.' Typical nemaline myopathy is the most common form, presenting as infantile hypotonia and muscle weakness. It is slowly progressive or nonprogressive, and most adults achieve ambulation. The severe form of the disorder is characterized by absence of spontaneous movement or respiration at birth, arthrogryposis, and death in the first months of life. Much less commonly, late-childhood or even adult-onset can occur. However, adult-onset nemaline myopathy is usually not familial and may represent a different disease (Wallgren-Pettersson et al., 1999; Sanoudou and Beggs, 2001). Myopathy caused by mutations in the ACTA1 gene can show a range of clinical and pathologic phenotypes. Some patients have classic rods, whereas others may also show intranuclear rods, clumped filaments, cores, or fiber-type disproportion (see 255310), all of which are nonspecific pathologic findings and not pathognomonic of a specific congenital myopathy. The spectrum of clinical phenotypes caused by mutations in ACTA1 may result from different mutations, modifying factors affecting the severity of the disorder, variability in clinical care, or a combination of these factors (Nowak et al., 1999; Kaindl et al., 2004). (161800) (Updated 08-Dec-2022)

MalaCards based summary: Nemaline Myopathy 3, also known as nemaline myopathy 3, autosomal dominant or recessive, is related to van der woude syndrome and nemaline myopathy 2, and has symptoms including waddling gait, generalized muscle weakness and facial paresis. An important gene associated with Nemaline Myopathy 3 is ACTA1 (Actin Alpha 1, Skeletal Muscle), and among its related pathways/superpathways is DNA repair pathways, full network. Affiliated tissues include skeletal muscle, and related phenotypes are hyperreflexia and dilated cardiomyopathy

MedlinePlus Genetics: ⁴² Actin-accumulation myopathy is a disorder that primarily affects skeletal muscles, which are muscles that the body uses for movement. People with actin-accumulation myopathy have severe muscle weakness (myopathy) and poor muscle tone (hypotonia) throughout the body. Signs and symptoms of this condition are apparent in infancy and include feeding and swallowing difficulties, a weak cry, and difficulty with controlling head movements. Affected babies are sometimes described as "floppy" and may be unable to move on their own.The severe muscle weakness that occurs in actin-accumulation myopathy also affects the muscles used for breathing. Individuals with this disorder may take shallow breaths (hypoventilate), especially during sleep, resulting in a shortage of oxygen and a buildup of carbon dioxide in the blood. Frequent respiratory infections and life-threatening breathing difficulties can occur. Because of the respiratory problems, most affected individuals do not survive past infancy. Those who do survive have delayed development of motor skills such as sitting, crawling, standing, and walking.The name actin-accumulation myopathy derives from characteristic accumulations in muscle cells of filaments composed of a protein called actin. These filaments can be seen when muscle tissue is viewed under a microscope.

Orphanet: ⁵⁸ A rare, genetic, congenital myopathy disorder characterized by variable degrees of muscular weakness, frequently associated with severe nemaline myopathy-like disease (including neonatal hypotonia, lack of spontaneous movements, feeding and swallowing difficulties, frequent respiratory infections, respiratory insufficiency, early death), and histopathologic findings of large, densely packed, subsarcolemmal accumulations of thin, actin-immunopositive filaments (with or without intranuclear nemaline rods) on muscle biopsy.

UniProtKB/Swiss-Prot ⁷³ Nemaline myopathy 3: A form of nemaline myopathy. Nemaline myopathies are muscular disorders characterized by muscle weakness of varying severity and onset, and abnormal thread-like or rod-shaped structures in muscle fibers on histologic examination.

Myopathy, actin, congenital, with excess of thin myofilaments: A congenital muscular disorder characterized at histological level by areas of sarcoplasm devoid of normal myofibrils and mitochondria, and replaced with dense masses of thin filaments. Central cores, rods, ragged red fibers, and necrosis are absent.

Disease Ontology: ¹¹ A nemaline myopathy that has material basis in homozygous, compound heterozygous, or heterozygous mutation in the ACTA1 gene on chromosome 1q42.

Wikipedia: ⁷⁵ Nemaline myopathy (also called rod myopathy or nemaline rod myopathy) is a congenital, often hereditary... more...

Clinical features from OMIM®:

Search Clinical Trials, NIH Clinical Center for Nemaline Myopathy 3