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FHL1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

FHL1 gene

The FHL1 gene provides instructions for proteins that play a vital role in the structure and function of skeletal and cardiac muscles.

Normal Function

The FHL1 gene provides instructions for making three versions (isoforms) of a protein: FHL1A (the full-length isoform), FHL1B, and FHL1C. These proteins are important in skeletal muscles (used for movement) and cardiac muscle (the heart).

FHL1A is the best-studied isoform and plays a critical role in the assembly of sarcomeres, the structures within muscle cells necessary for contraction. It is also involved in chemical signaling, maintaining cell structure, and influencing muscle growth. While less is known about FHL1B and FHL1C, they are suspected to contribute to the normal structure and function of skeletal and cardiac muscles.

Health Conditions Related to Genetic Changes

Emery-Dreifuss muscular dystrophy

At least seven mutations in the FHL1 gene have been found to cause Emery-Dreifuss muscular dystrophy. This condition affects skeletal and cardiac muscle, leading to:

  • Contractures: Joint deformities that restrict movement.
  • Muscle wasting: Weakness and wasting that worsen over time.
  • Heart problems: An increased risk of sudden death.

These mutations affect the FHL1A isoform, reducing the amount of functional protein or creating a nonfunctional version, which disrupts muscle cell structure and function.

Other disorders

Other muscle disorders resulting from FHL1 mutations are collectively known as FHL1-related myopathies or FHL1opathies. These include:

  • Reducing body myopathy
  • X-linked scapuloperoneal myopathy
  • X-linked myopathy with postural muscle atrophy (XMPMA)
  • Rigid spine syndrome

Common features include skeletal muscle weakness (particularly in shoulders and lower legs), rigid spine, and heart abnormalities. In some cases, mutations lead to the production of abnormal proteins that form clumps called reducing bodies within muscle cells.

Other Names for This Gene

  • bA535K18.1, FHL-1, FHL1A, FHL1B, FLH1A
  • four-and-a-half Lin11, Isl-1 and Mec-3 domains 1
  • KYO-T, KYOT, LIM protein SLIMMER, MGC111107
  • RBMX1A, RBMX1B, skeletal muscle LIM-protein 1
  • SLIM, SLIM-1, SLIM1, SLIMMER, XMPMA

Frequently Asked Questions

Key red flags include early‑onset progressive muscle weakness that disproportionately affects the shoulders and lower legs, joint contractures (especially in the elbows and ankles), a rigid spine, and a family history of Emery‑Dreifuss muscular dystrophy or other X‑linked myopathies. If a young adult presents with unexplained fatigue, shortness of breath, or arrhythmias alongside these musculoskeletal findings, an FHL1 genetic test should be considered.
Management is largely supportive. Physical therapy focused on stretching and strengthening can help maintain mobility. Respiratory support, such as non‑invasive ventilation, may be needed if diaphragmatic weakness develops. While no disease‑modifying drugs are approved specifically for FHL1 myopathies, clinical trials investigating gene therapy, antisense oligonucleotides, or small‑molecule modulators of sarcomere function are ongoing. Patients should be screened for eligibility in such trials.
Emery‑Dreifuss muscular dystrophy is X‑linked recessive; male offspring of an affected mother have a 50% chance of inheriting the mutation, while female offspring have a 50% chance of being carriers. Genetic counseling is essential to discuss options such as prenatal testing (chorionic villus sampling or amniocentesis) or pre‑implantation genetic diagnosis (PGD) with IVF. For children who are carriers or affected, early referral to a neuromuscular specialist for baseline cardiac and muscular assessment is recommended.
FHL1 mutations can disrupt sarcomere structure in cardiac muscle, predisposing to arrhythmias such as atrial fibrillation, ventricular tachycardia, or heart block. Sudden cardiac death may occur during exertion or at rest. Regular cardiac evaluation—including ECG, Holter monitoring, echocardiography, and, if indicated, cardiac MRI—should be performed at least annually. Patients with known arrhythmias may benefit from an implantable cardioverter‑defibrillator (ICD) after a risk assessment by a cardiologist.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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