An Ultra-Rare Manifestation of an X-Linked Recessive Disorder: Duchenne Muscular Dystrophy in a Female Patient

Duchenne muscular dystrophy (DMD) is the most common inherited muscle dystrophy. Patients are characterized by muscle weakness, gross motor delay, and elevated serum creatinine kinase (CK) levels. The disease is caused by mutations in the DMD gene located on the X chromosome. Due to the X-linked recessive inheritance pattern, DMD most commonly affects males, who are generally diagnosed between the age of 3–5 years. Here we present an ultra-rare manifestation of DMD in a female patient. Cytogenetic examination showed that she has a t(X;10)(p21.1;p12.1) translocation, which turned out to affect the DMD gene with one of the breakpoints located in exon 54 (detected by genome sequencing). The X-inactivation test revealed skewed X-inactivation (ratio 99:1). Muscle histology and dystrophin immunohistochemistry showed severe dystrophic changes and highly reduced dystrophin expression, respectively. These results, in accordance with the clinical picture and a highly elevated serum CK, led to the diagnosis of DMD. In conclusion, although in very rare cases, DMD can manifest in female patients as well. In this case, a balanced X-autosome reciprocal translocation disrupts the DMD gene and skewed X-inactivation leads to the manifestation of the DMD phenotype.

Newborn Screening for Duchenne Muscular Dystrophy: First Year Results of a Population-Based Pilot

Advancements in therapies for Duchenne muscular dystrophy (DMD) have made diagnosis within the newborn period a high priority. We undertook a consortia approach to advance DMD newborn screening in the United States. This manuscript describes the formation of the Duchenne Newborn Screening Consortium, the development of the pilot protocols, data collection tools including parent surveys, and findings from the first year of a two-year pilot. The DMD pilot design is population-based recruitment of infants born in New York State. Data tools were developed to document the analytical and clinical validity of DMD NBS, capture parental attitudes, and collect longitudinal health information for diagnosed newborns. Data visualizations were updated monthly to inform the consortium on enrollment. After 12 months, 15,754 newborns were screened for DMD by the New York State Newborn Screening (NYS NBS) Program. One hundred and forty screened infants had borderline screening results, and sixteen infants were referred for molecular testing. Three male infants were diagnosed with dystrophinopathy. Data from the first year of a two-year NBS pilot for DMD demonstrate the feasibility of NBS for DMD. The consortia approach was found to be a useful model, and the Newborn Screening Translational Research Network's data tools played a key role in describing the NBS pilot findings and engaging stakeholders.

Newborn screening for Duchenne muscular dystrophy-early detection and diagnostic algorithm for female carriers of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most common pediatric-onset form of muscular dystrophy, occurring in 1 in 5,000 live male births. DMD is a multi-system disease resulting in muscle weakness with progressive deterioration of skeletal, heart, and smooth muscle, and learning disabilities. Pathogenic/likely pathogenic (P/LP) variants in the DMD gene, which encodes dystrophin protein, cause dystrophinopathy. All males with a P/LP variant in the X-linked DMD gene are expected to be affected. Two to 20% of female heterozygotes with a P/LP variant develop symptoms of dystrophinopathy ranging from mild muscle weakness to significant disability similar to Becker muscular dystrophy. Recently, with improvements in therapies and testing methodology, there is stronger evidence supporting newborn screening (NBS) for DMD for males and females because females may also develop symptoms. A consented pilot study to screen newborns for DMD was initiated in New York State (NYS) and conducted from 2019 to 2021. The identification of female carriers and the realization of the subsequent uncertainty of providers concerning follow-up during the pilot led to the development of algorithms for screening and diagnosis of carrier females, including both NBS and cascade molecular testing of family members.

Not just carriers: experiences of X-linked female heterozygotes

PURPOSE

To better understand the needs and experiences of the X-linked carrier community to improve future recognition, diagnosis, and treatment by bringing X-linked carrier voices together.

METHODS

An anonymous survey link was distributed to members of Remember the Girls, a non-profit organization for female (XX) carriers of X-linked conditions, through its website, Facebook group, Instagram, and Twitter. The survey was developed to gather data on XX carriers of numerous X-linked conditions.

RESULTS

One hundred and fifty individuals participated in the study. The majority (81/150) of individuals learned about their carrier status by giving birth to a son diagnosed with an X-linked condition. However, over 80% (120/145) believed that they should learn this information before the age of 18. Over 80% of participants (124/148) felt that they either have or may have symptoms attributable to their X-linked condition. Yet, only 10.1% (15/148) felt that they had sufficient access to knowledgeable healthcare providers and/or medical information. Additionally, 46.7% (70/150) of participants reported that healthcare providers did not discuss reproductive options with them. Improving carrier access to medical information, research studies, new treatments, and reproductive methods was found to be the top priority.

CONCLUSION

Limited information exists on X-linked carriers' risk for symptoms and there is a lack of available treatments. This study demonstrates the need for more knowledgeable healthcare providers and medical information within the X-linked carrier community.

Impact of estrogen deficiency on diaphragm and leg muscle contractile function in female mdx mice

Female carriers of Duchenne muscular dystrophy (DMD) presenting with DMD symptomology similar to males with DMD, such as skeletal muscle weakness and cardiomyopathy, are termed manifesting carriers. There is phenotypic variability among manifesting carriers including the age of onset, which can range from the first to fourth decade of life. In females, estrogen levels typically begin to decline during the fourth decade of life and estrogen deficiency contributes to loss of muscle strength and recovery of strength following injury. Thus, we questioned whether the decline of estrogen impacts the development of DMD symptoms in females. To address this question, we studied 6-8 month-old homozygous mdx female mice randomly assigned to a sham or ovariectomy (OVX) surgical group. In vivo whole-body plethysmography assessed ventilatory function and diaphragm muscle strength was measured in vitro before and after fatigue. Anterior crural muscles were analyzed in vivo for contractile function, fatigue, and in response to eccentric contraction (ECC)-induced injury. For the latter, 50 maximal ECCs were performed by the anterior crural muscles to induce injury. Body mass, uterine mass, hypoxia-hypercapnia ventilatory response, and fatigue index were analyzed by a pooled unpaired t-test. A two-way ANOVA was used to analyze ventilatory measurements. Fatigue and ECC-injury recovery experiments were analyzed by a two-way repeated-measures ANOVA. Results show no differences between sham and OVX mdx mice in ventilatory function, strength, or recovery of strength after fatigue in the diaphragm muscle or anterior crural muscles (p ≥ 0.078). However, OVX mice had significantly greater eccentric torque loss and blunted recovery of strength after ECC-induced injury compared to sham mice (p ≤ 0.019). Although the results show that loss of estrogen has minimal impact on skeletal muscle contractile function in female mdx mice, a key finding suggests that estrogen is important in muscle recovery in female mdx mice after injury.

Recurrent Exercise-Induced Rhabdomyolysis in a Healthy Adolescent Girl

Female symptomatic carriers of Duchenne muscular dystrophy (DMD) are uncommon findings. Much of this disease has been studied from a male perspective, but female disease presentation and progression are rarely described. This report describes a female adolescent patient with a rare and unconventional presentation of DMD.

Clinical and Genetic Characterization of Female Dystrophinopathy

BACKGROUND AND PURPOSE

Duchenne and Becker muscular dystrophies are the most common X-linked recessive muscular dystrophies. Dystrophin gene mutations usually affect men, but reportedly 2.5-7.8% of women are affected and are classified as symptomatic carriers. The aim of this study was to clinically and genetically characterize symptomatic female dystrophinopathy carriers.

METHODS

The clinical and genetic data of 11 female dystrophinopathy carriers among 285 patients who underwent multiplex ligation-dependent probe amplification (MLPA) analysis for the dystrophin gene were reviewed. Women with muscle weakness and/or dilated cardiomyopathy were classified as symptomatic carriers, while subjects with high serum creatine kinase (CK) levels and/or minor myopathic signs such as muscle cramps and myalgia were classified as asymptomatic.

RESULTS

Twelve female carriers were identified, but 1 symptomatic carrier who also had Turner syndrome was excluded from the study. Of the 11 included female carriers, 4 were symptomatic and 7 were asymptomatic. The age at symptom onset in the symptomatic female carriers ranged from 15 to 31 years (mean, 30.6 years), and the age at diagnosis for asymptomatic carriers ranged from 4 to 38 years (mean, 24.5 years). Serum CK levels were markedly elevated (mean, 1,301 IU/mL) in three of the four (75%) symptomatic female carriers, and mildly elevated in three of the seven (42%) asymptomatic female carriers. Symptomatic female carriers typically presented with asymmetric bilateral leg weakness as the initial symptom, with aggravated symptoms after labor.

CONCLUSIONS

Female dystrophinopathy is not uncommon, and it is an important factor with respect to males with dystrophinopathy who may be born to such patients. Screening with MLPA is useful because it can aid in early diagnosis and appropriate management.