Sign Up for a Free Account
  • Updated 12.13.2025
  • Released 04.26.1994
  • Expires For CME 12.13.2028

X-linked myotubular myopathy

Authors
Haluk Topaloglu MD, Gulcin Akinci MD
See Contributor Disclosures
Editor
Harvey B Sarnat MD FRCPC MS
Cite this article

Cite this article

Introduction

Overview

X-linked myotubular myopathy is a severe form of centronuclear myopathy caused by mutations in the myotubularin (MTM1) gene. The condition primarily affects males and is typically characterized by neonatal-onset hypotonia, muscle weakness, and significant bulbar and respiratory involvement, leading to early mortality. With advanced intensive care, survival has improved; however, the overall disease burden remains high. Therapeutic management of X-linked myotubular myopathy remains challenging, although multiple approaches are being explored. Preclinical models and early phase clinical trials have examined AAV mediated gene replacement, drug repurposing, and antisense oligonucleotides. Although several therapeutic strategies progressed to clinical trials, development was halted due to safety concerns, and effective treatment remains an unmet need. Recent observations also highlight liver involvement as a prominent feature of the disease, creating important safety considerations for future gene based treatment strategies.

Key points

• X-linked myotubular myopathy is caused by mutations in the myotubularin gene MTM1.

• Molecular genetic verification is often possible through sequencing, but it should be noted that copy number variations may also be causative, as may intronic alterations, and this may require other analytic methods.

• Most, but not all, mothers of affected boys are mutation carriers; mosaicism has been reported.

• Female carriers may present with overt disease.

• Differential diagnoses include the autosomal forms of centronuclear myopathy and myotonic dystrophy.

• Hepatobiliary disease is quite common and should be carefully monitored.

• Although no curative treatment exists to date for this usually very severe disorder, active treatment is indicated, at least initially, because of the favorable course in some neonatally severe cases.

• Multidisciplinary trial design is crucial to safely advance new therapies in X-linked myotubular myopathy.

Historical note and terminology

X-linked myotubular myopathy (OMIM #310400) is the most severe form of the centronuclear myopathies (69; 104). These myopathies were defined after the advent of histochemical staining methods of muscle biopsy sections on the basis of structural abnormalities in the muscle fibers.

Centronuclear myopathies are characterized by the presence of centrally located nuclei in muscle fibers. This term is used to describe a diverse collection of individually rare congenital myopathies. These conditions are primarily caused by pathogenic variants in MTM1 (approximately 50%), DNM2 (approximately 15%), or BIN1 (approximately 3%). Although a significant percentage (approximately 20%) of centronuclear myopathy cases have an unknown genetic basis, another portion (approximately 12%) involves other genes (24). The centronuclear myopathy–like phenotype has been reported to be associated with pathogenic variants in genes, such as ryanodine receptor 1 (RYR1) (243), titin (TTN) (41), SPEG (01), ZAK (230), DHPR (CACNA1S) (196), and potentially CCDC78 (154) and myotubularin-related protein 14 (MTMR14) (222). In a Myocapture study, pathogenic variants in the OPA1 and FOXP3 genes were identified in families with centronuclear myopathy (59). Centronuclear myopathies, despite their diverse presentations and modes of inheritance, often show noticeable weakness in the eye muscles, such as ptosis and ophthalmoparesis. In 1966, findings of muscle pathology were reported in a 12-year-old boy who exhibited generalized muscle wasting and facial weakness, including ptosis (207). The authors of this report were surprised to find that the images of the affected muscle fibers closely resembled fetal myotubes. These myotubes appeared slightly elongated, having a central nucleus with one or a few myofibrils. The authors hypothesized that this condition arose from an interruption in the development of muscle fibers and proposed the term “myotubular myopathy” to describe the condition. Although the exact nature of this disease is not yet fully understood, "myotubular myopathy" remains the designated term for the X-linked inherited type of centronuclear myopathy.

In 1969, the X-linked form of myotubular myopathy was described in a large Dutch pedigree in which the affected males showed muscle fibers resembling fetal myotubes (229). A long-term follow-up study of this and another Dutch family shows wide variability in the clinical picture (12), confirmed by reports of patients diagnosed as adults (111; 174).

Myotubes in fetal muscle (photomicrographs)
Transverse sections of quadriceps femoris muscle of a 14-week human fetus (left) and a term neonate with X-linked myotubular myopathy (right). In the fetal muscle, both early and late myotubes are seen; the early fibers have scant...

The coining of the alternative name "centronuclear" myopathy reflects the argument about whether the basic defect in this disorder is an arrest of maturation of the fetal muscle fibers or whether the central nuclei constitute the main histologic feature.

Central nuclei in muscle fiber (photomicrographs)
Longitudinal sections of quadriceps femoris muscle of a 14-week human fetus (left) and a term neonate with X-linked myotubular myopathy (right). In both true fetal myotubes and the centronuclear fibers of myotubular myopathy, the ...

In 1985, eight patients with muscle biopsies showing a centronuclear myopathy pattern were reported (104). The authors of this report proposed three inheritance patterns in this group of patients. They observed that the individuals they identified as having X-linked inheritance were male and displayed a severe phenotype, including neonatal asphyxia, difficulties with breathing and feeding shortly after birth, as well as weakness in the face and limbs during the neonatal period, often leading to early mortality.

In 1996, a consortium of three groups found mutations within the MTM1 gene located on the X chromosome as the underlying cause of this condition (137). The final product of this gene, known as myotubularin (MTM1), is recognized as an enzyme found in endosomes. It plays a role as endosomal lipid phosphatase, which regulates membrane trafficking by modulating phosphoinositide (PI) dephosphorylation and contributes to the structure and function of muscle fibers.

The first disease model of X-linked myotubular myopathy using knockout mice was established in 2002 (37), followed by the development of other animal models (68; 175) and natural disease models in canines (15; 88; 170). These initiatives have led to a better understanding of disease pathogenesis and treatment targets.

Autosomal forms with similar histology have been described (OMIM #60150, #255200). They usually present later and follow a milder course than the X-linked form (237; 114), in dogs also (204), but exceptionally severe cases similar to the X-linked form have also been reported (121; 26). Mutations in the dynamin 2 gene (29) are a common cause of the dominantly inherited form (76; 28; 72; 197), whereas mutations in the ryanodine receptor gene RYR1 have also been identified, including recessively inherited mutations (122; 243; 23; 121).

The first causative gene for autosomal recessive centronuclear myopathy was identified as amphiphysin 2 (BIN1) (167). Subsequently, a patient with internalized nuclei, the histopathology resembling centronuclear myopathy, was found to have compound heterozygous mutations in the titin gene TTN (41; 65). A further differential diagnosis may be myopathy caused by SPEG mutations, often accompanied by cardiomyopathy (01; 240; 241).

It is to be noted that female carriers of the X-linked form can manifest muscle disease, as index patients, also, with no affected males known in the family (102; 235; 210; 117; 130; 195; 96; 174; 24; 105; 121; 74; 194; 27; 83; 247; 46; 128). A female patient described with cardiomyopathy requiring heart transplantation had not undergone analysis of the myotubularin gene.

This is an article preview.
Start a Free Account
to access the full version.

  • Nearly 3,000 illustrations, including video clips of neurologic disorders.

  • Every article is reviewed by our esteemed Editorial Board for accuracy and currency.

  • Full spectrum of neurology in 1,200 comprehensive articles.

  • Listen to MedLink on the go with Audio versions of each article.

Questions or Comment?

MedLink, LLC

3525 Del Mar Heights Rd, Ste 304
San Diego, CA 92130-2122

Toll Free (U.S. + Canada): 800-452-2400

US Number: +1-619-640-4660

Support: service@medlink.com

Editor: editor@medlink.com

ISSN: 2831-9125