Muscle, cardiac, and cerebral manifestations in female carriers of dystrophin variants

Cardiomyopathies in Women

Heart failure affects over 2.6 million people in the United States. While women have better overall survival rates, they also suffer from higher morbidity as shown by higher rates of hospitalization and worse quality of life. Several anatomical differences in women's hearts affect both systolic and diastolic cardiac physiology. Despite these findings, women are significantly underrepresented in clinical trials, necessitating extrapolation of data from males. Because women have sex-specific etiologies of heart failure and unique manifestations in genetic-related cardiomyopathies, meaningful sex-related differences affect heart failure outcomes as well as access to and outcomes in advanced heart failure therapies in women. This review explores these gender-specific differences and potential solutions to balance care between women and men.

Drug-refractory Heart Failure in Female Carrier of Duchenne Muscular Dystrophy: A Case of X-linked Dilated Cardiomyopathy

A 56-year-old woman was referred to our hospital for the further evaluation of drug-refractory heart failure with a reduced ejection fraction. A family history interview revealed that men in her family had died of Duchenne muscular dystrophy (DMD), whereas she had no skeletal muscle disorder. Myocardial histopathology revealed a reduced dystrophin expression in the cardiomyocyte membrane, and a dystrophin (DMD) gene analysis identified a duplication in exon 8-9 on Xp21, suggesting that she had a cardiac-specific phenotype of dystrophinopathy, i.e. X-linked dilated cardiomyopathy (XLDCM). In conclusion, careful family history interviews and an investigation of dystrophinopathy are required to detect XLDCM in women.

Intellectual disability in paediatric patients with genetic muscle diseases

The differential diagnosis of genetic muscle disease has become increasingly difficult due to the rapid progress in genetic medicine in recent years. Where classifications based on the clinical picture were attributed to one gene only a few years ago, today we know that a variety of clinical presentations can result from the same mutation and, conversely, various genes are associated with a similar phenotype. A significant consideration in assessing a patient with muscle weakness is the presence or absence of intellectual disability, thus narrowing the differential diagnostic approach in any child with an as yet undiagnosed muscle disease. Intellectual disability in neuromuscular diseases is often associated with behavioural disorders and may be correlated with abnormal brain imaging. Conversely, brain involvement can sometimes be seen without intellectual disability, but may be associated with an epilepsy risk and is helpful for the differential diagnosis. This review focuses on the three most common causes of paediatric muscle diseases with intellectual disability, dystrophinopathies, myotonic dystrophy type 1 and dystroglycanopathies. It also summarises differential diagnostic considerations when assessing a child with a genetic muscle disease and intellectual disability. The recent scientific literature on this topic is reviewed, the frequency of intellectual disability assessed, and specific clinical features are described. Where available, data on disease onset, progression and serum creatine kinase levels are presented and the pattern of muscle involvement described in an algorithm. Central nervous involvement and brain imaging analysis was reviewed and included.

Spinal muscular atrophy: Broad disease spectrum and sex-specific phenotypes

Spinal muscular atrophy (SMA) is one of the major genetic disorders associated with infant mortality. More than 90% of cases of SMA result from deletions of or mutations in the Survival Motor Neuron 1 (SMN1) gene. SMN2, a nearly identical copy of SMN1, does not compensate for the loss of SMN1 due to predominant skipping of exon 7. The spectrum of SMA is broad, ranging from prenatal death to infant mortality to survival into adulthood. All tissues, including brain, spinal cord, bone, skeletal muscle, heart, lung, liver, pancreas, gastrointestinal tract, kidney, spleen, ovary and testis, are directly and/or indirectly affected in SMA. Accumulating evidence on impaired mitochondrial biogenesis and defects in X chromosome-linked modifying factors, coupled with the sexual dimorphic nature of many tissues, point to sex-specific vulnerabilities in SMA. Here we review the role of sex in the pathogenesis of SMA.

Duchenne Dilated Cardiomyopathy: Cardiac Management from Prevention to Advanced Cardiovascular Therapies

Duchenne muscular dystrophy (DMD) cardiomyopathy (DCM) is characterized by a hypokinetic, dilated phenotype progressively increasing with age. Regular cardiac care is crucial in DMD care. Early recognition and prophylactic use of angiotensin converting enzyme inhibitors (ACEi) are the main stay therapeutic strategy to delay incidence of DMD-DCM. Pharmacological treatment to improve symptoms and left ventricle (LV) systolic function, have been widely implemented in the past years. Because of lack of DMD specific drugs, actual indications for established DCM include current treatment for heart failure (HF). This review focuses on current HF strategies to identify, characterize, and treat DMD-DCM.

Cardiac Involvement in Dystrophin-Deficient Females: Current Understanding and Implications for the Treatment of Dystrophinopathies

Duchenne muscular dystrophy (DMD) is a fatal X-linked recessive condition caused primarily by out-of-frame mutations in the dystrophin gene. In males, DMD presents with progressive body-wide muscle deterioration, culminating in death as a result of cardiac or respiratory failure. A milder form of DMD exists, called Becker muscular dystrophy (BMD), which is typically caused by in-frame dystrophin gene mutations. It should be emphasized that DMD and BMD are not exclusive to males, as some female dystrophin mutation carriers do present with similar symptoms, generally at reduced levels of severity. Cardiac involvement in particular is a pressing concern among manifesting females, as it may develop into serious heart failure or could predispose them to certain risks during pregnancy or daily life activities. It is known that about 8% of carriers present with dilated cardiomyopathy, though it may vary from 0% to 16.7%, depending on if the carrier is classified as having DMD or BMD. Understanding the genetic and molecular mechanisms underlying cardiac manifestations in dystrophin-deficient females is therefore of critical importance. In this article, we review available information from the literature on this subject, as well as discuss the implications of female carrier studies on the development of therapies aiming to increase dystrophin levels in the heart.