Is Nemaline Myopathy hereditary?

Nemaline Myopathy is a genetically determined muscle disorder that is hereditary, meaning it is caused by pathogenic variants in specific genes passed from parents to children. While most cases follow an autosomal recessive inheritance pattern, Nemaline Myopathy can also be inherited in an autosomal dominant manner or occur as a spontaneous (de novo) mutation.

How is Nemaline Myopathy inherited?

The inheritance of Nemaline Myopathy depends on the specific gene involved, such as NEB, ACTA1, or TPM3. In autosomal recessive cases, both parents are typically asymptomatic carriers, and there is a 25% risk for each child to inherit the condition. In autosomal dominant cases, an affected parent has a 50% risk of passing the gene to their child. Because Nemaline Myopathy is highly genetically heterogeneous, the inheritance risk is highly specific to the identified mutation within a family.

Are de novo mutations common in Nemaline Myopathy?

Yes, de novo mutations are frequently observed in Nemaline Myopathy, particularly in cases involving the ACTA1 gene. A de novo mutation means the genetic change occurred spontaneously in the egg or sperm cell, and neither parent carries the mutation. In these instances, the risk of recurrence for future siblings is generally low, though germline mosaicism—where a parent carries the mutation in their reproductive cells but not their blood—remains a rare possibility.

What are the options for genetic testing and counseling?

Genetic testing is the gold standard for confirming a diagnosis of Nemaline Myopathy. Clinical geneticists recommend the following steps for families:

• Diagnostic Testing: Comprehensive gene panels or whole-exome sequencing to identify the causative mutation.


• Carrier Testing: Offered to biological relatives once a specific familial mutation is identified.


• Prenatal Diagnosis: Options such as CVS or amniocentesis for pregnancies where the recurrence risk is known.


• Preimplantation Genetic Testing (PGT): Allows families to screen embryos during IVF to select those without the specific Nemaline Myopathy mutation.

Next steps

• Consult with a board-certified clinical geneticist to discuss your specific genetic test results.


• Connect with the 102 members of the DiseaseMaps.org community who are living with Nemaline Myopathy to share experiences.


• Request a referral to a genetic counselor to map out family inheritance patterns before planning a pregnancy.

Medical disclaimer: This information is for educational purposes only and does not replace professional medical advice, diagnosis, or treatment.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Nemaline Myopathy.


• Orphanet: Nemaline Myopathy (ORPHA:606).


• Online Mendelian Inheritance in Man (OMIM): #161800 (Nemaline Myopathy 1).


• The A Foundation for Nemaline Myopathy: Patient and family resources.