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Congenital Muscular Dystrophy

CMD

Congenital muscular dystrophy (CMD) is a general term referring to a group of hereditary diseases characterized by early-onset hypotonia and muscle weakness, progressive muscle wasting, and possibly ocular and central nervous system malformations. Disease severity, quality of life and life expectancy varies from patient to patient. Causal treatment is not available and only supportive therapy can be provided. The latter typically comprises physical therapy, orthopedic devices, surgical interventions, and respiratory support, if needed.


Presentation

Congenital hypotonia and poor spontaneous movement often constitute the first findings in CMD patients [1]. Those neonates are also called "floppy infants". They may face enormous difficulties with respiration and the ingestion of food. Such severe disease usually entails a very short life expectancy. Individuals suffering from milder CMD show mild to moderate delays of motor development; they may or may not reach independent ambulation. Parents of children suffering from milder CMD are often unable to clearly define a time of symptom onset. They may present their child due to delayed attainment of gross motor milestones in infancy or childhood. In any case, muscle weakness augments over time. Initially unremarkable facial features tend to change and CMD patients eventually acquire myopathic facial characteristics. Macrocephaly may be noted. Additionally, joint mobility continually decreases and patients are prone to develop spinal deformities such as scoliosis, kyphosis and lordosis. If independent ambulation has been reached, it may be lost.

Muscular dystrophy may affect the eye muscles and CMD patients may develop ophthalmoplegia. Furthermore, malformations of ocular structures may be seen in those affected by CMD. In detail, microphthalmia, microcornea, iris hypoplasia, narrow anterior chamber angle with subsequent glaucoma, cataracts, retinal colobomas and detachment, hypoplastic or absent optic nerves have been described in CMD patients, particularly in those with abnormal glycosylation of α-dystroglycan [1].

Cardiac involvement is seen in some types of CMD. Patients may suffer from primary cardiomyopathy or arrhythmia, but may also develop right heart failure secondary to restrictive lung disease.

Besides muscular dystrophy and ocular malformation, central nervous system disorders are a hallmark of many types of CMD. Indeed, central nervous system involvement is one of the most important parameters when establishing the diagnosis: It is to be expected in most α-dystroglycanopathies, except in CMD type 1C [2]. In CMD type 1A, mental retardation is rarely observed and seizures affect up to 30% of affected individuals only, but brain imaging may reveal white matter anomalies [1]. Disturbances of mental development is not typical of CMD type Ullrich and Bethlem myopathy.

Weakness
  • The patients developed exacerbation of muscle weakness ranging from paralysis to loss of head control. The onset was concentrated in summer, and coxsackieviruses and enteroviruses were most often detected, especially in infantile patients.[ncbi.nlm.nih.gov]
  • These siblings, aged 37 and 40, are cognitively normal with mild non-progressive muscle weakness and a susceptibility to rhabdomyolysis.[ncbi.nlm.nih.gov]
  • The first signs of the disorder appear in early infancy and include a weak cry, poor feeding, and weak muscle tone (hypotonia).[ghr.nlm.nih.gov]
  • We have re-examined six patients and found permanent limb-girdle weakness, but also episodic crises without clear precipitating factors.[ncbi.nlm.nih.gov]
  • Congenital muscular dystrophy related to lamin A/C is rare and characterized by early-onset hypotonia with axial muscle weakness typically presenting with a loss in motor acquisitions within the first year of life and a dropped-head phenotype.[ncbi.nlm.nih.gov]
Feeding Difficulties
  • People with CMDs are often afflicted with a wide range of health complications, including cognitive impairment, respiratory complications, cardiac complications, feeding difficulties, scoliosis, and nutritional deficiencies.[neurologyadvisor.com]
  • Some infants may experience respiratory and feeding difficulties shortly after birth (neonatal period). Feeding difficulties may result in affected children failing to gain weight and grow at the expected rate (failure to thrive).[rarediseases.org]
  • Merosin Positive CMD The term, 'Merosin Positive CMD,' refers to persons who fit a CMD picture with floppy muscle tone and may present with respiratory and feeding difficulty, and whose muscle shows the presence of Merosin and a Dystrophic pattern.[disabled-world.com]
  • difficulties at birth and markedly delayed motor milestones.[healio.com]
Difficulty Walking
  • Persons affected with RSMD1 experience difficulty walking due to thigh muscle weakness, spinal rigidity, and mild Achilles tendon tightness.[disabled-world.com]
  • Most individuals are able to walk independently although because of progressive spinal rigidity and scoliosis they may experience difficulties walking later during life.[rarediseases.org]
  • The weakness progresses slowly, so that in their 40s and 50s, men with this condition may have difficulty walking. Weakness of the heart and breathing muscles can occur and may need treatment.[patient.info]
Congestive Heart Failure
  • Congestive Heart failure Hypoglycemia – Low blood sugar may lead to floppiness of the muscles Myasthenia gravis – is an autoimmune disease that disrupts signals between nerves and muscles and affects the neuromuscular junction.[news-medical.net]
Anemia
  • A CELLULE FALCIFORMI ANEMIA CONGENITA DISERITROPOIETICA ANEMIA DI FANCONI ANEMIA SIDEROBLASTICA ANGELMAN SINDROME DI ANGIOEDEMA DI QUINCK ANGIOMA ANOMALIA MITRALICA CONGENITA ANTICORPI ANTIFOSFOLIPIDI SINDROME DA APERT SINDROME DI ARNOLD CHIARI SINDROME[birdfoundation.org]
Dysphagia
  • Mechanical insufflation-exsufflation (MI-E) interventions were also employed in six patients with serious dysphagia and were well-tolerated in all cases.[ncbi.nlm.nih.gov]
  • An autosomal dominant hereditary disease that presents in late in life and is characterized by dysphagia and progressive ptosis of the eyelids.[icd10data.com]
Macroglossia
  • Additional symptoms may occur including overgrowth (hypertrophy) of the muscles of the legs, an abnormally enlarged tongue (macroglossia), weakness and wasting (atrophy) of the muscles of the arms, and contractures, especially of the Achilles tendon,[rarediseases.org]
Heart Block
  • This may cause a slow heartbeat (called heart block) and symptoms of tiredness, giddiness or fainting. This can be treated with a heart pacemaker. For this reason, regular heart checks are recommended for people with Emery-Dreifuss MD.[patient.info]
Jaundice
  • Brain and spinal cord injury that may include bleeding into the brain Serious infections of the brain and its parts like meningitis or encephalitis Kernicterus – This condition is severe affliction of the brain of the new born with bilirubin from the jaundice[news-medical.net]
Follicular Hyperkeratosis
  • Joint hyperlaxity and skin changes (follicular hyperkeratosis and muscle biopsy scar thinning) were unique to COL6A. Severe scoliosis, macrocephaly, and nonambulatory status were common in LAMA2.[ncbi.nlm.nih.gov]
  • UCMD patients usually have dry soft skin and follicular hyperkeratosis over the extensor surfaces of the extremities. Early respiratory failure is a common complication and potential cause of death.[orpha.net]
  • Other characteristic findings include protrusion of the calcanei, follicular hyperkeratosis, and a predisposition to hypertrophie (keloid) scars.19,20 Serum creatine kinase (CK) is normal or only mildly elevated in Ullrich CMD.[healio.com]
Strabismus
  • Several patients have had strabismus. Systemic Features: Progressive muscle weakness begins in early childhood. Hypotonia is usually present at birth followed by atrophy of the proximal muscles (especially in the lower limbs).[disorders.eyes.arizona.edu]
  • Individuals with FCMD also have eye (ocular) abnormalities such as crossed eyes (strabismus), cataracts, nearsightedness (myopia), abnormal eye movements, and, in severe cases, retinal detachment and abnormally small eyes (microphthalmos).[rarediseases.org]
Muscle Weakness
  • The patients developed exacerbation of muscle weakness ranging from paralysis to loss of head control. The onset was concentrated in summer, and coxsackieviruses and enteroviruses were most often detected, especially in infantile patients.[ncbi.nlm.nih.gov]
  • Congenital muscular dystrophy related to lamin A/C is rare and characterized by early-onset hypotonia with axial muscle weakness typically presenting with a loss in motor acquisitions within the first year of life and a dropped-head phenotype.[ncbi.nlm.nih.gov]
  • Congenital muscular dystrophies are defined by congenital or infantile onset of muscle weakness; while 12 culprit genes have been identified, many cases remain molecularly uncharacterized.[ncbi.nlm.nih.gov]
  • JK.Janice.Ip@gmail.com Abstract Congenital muscular dystrophy (CMD) comprises a heterogeneous group of disorders present at birth with muscle weakness, hypotonia and contractures.[ncbi.nlm.nih.gov]
  • These siblings, aged 37 and 40, are cognitively normal with mild non-progressive muscle weakness and a susceptibility to rhabdomyolysis.[ncbi.nlm.nih.gov]
Muscular Atrophy
  • The objectives of this study were to determine the effects that routine daily home air-stacking maneuvers have on pulmonary function in patients with spinal muscular atrophy (SMA) and in patients with congenital muscular dystrophy (CMD), as well as to[ncbi.nlm.nih.gov]
  • Differential diagnosis In the neonatal period, the differential diagnoses include Bethlem myopathy and other forms of congenitalmuscular dystrophy (CMD) and myopathy, spinal muscular atrophy, forms of Ehlers-Danlos syndrome, and Marfan syndrome (see these[orpha.net]
  • atrophy Prader-Willi syndrome Tay-Sachs disease Trisomy 13 Other disorders that can lead to the condition include: Achondroplasia Being born with hypothyroidism Poisons or toxins Spinal cord injuries that occur around the time of birth Take extra care[nlm.nih.gov]
Hip Dislocation
  • dislocation and a type of curvature of the spine known as ’kyphoscoliosis’.[santhera.com]
  • Clinical description Weakness of the facial muscles, a high-arched palate, congenital hip dislocation, protrusion of the calcaneus, torticollis, transient kyphotic deformity, contractures (particularly involving the elbows and knees), and distal laxity[orpha.net]
  • dislocation, prominent ears, joint contractures, torticollis (a persistent tilting or turning of the head), and skin changes, among other symptoms.[disabilitybenefitscenter.org]
  • Persons with UCMD commonly experience muscle weakness, kyphoscoliosis, hip dislocation at birth, prominent heel bones, hyper-pigmented skin lesions, hyper-extensible finger joints, and elbow contractures.[disabled-world.com]
Muscle Hypotonia
  • Muscle tone and movement involve the brain, spinal cord, nerves, and muscles. Hypotonia may be a sign of a problem anywhere along the pathway that controls muscle movement.[nlm.nih.gov]
Joint Stiffness
  • CMD results in overall muscle weakness with possible joint stiffness or looseness. Depending on the type, CMD may involve spinal curvature, respiratory insufficiency, intellectual disabilities, learning disabilities, eye defects or seizures.[mda.org]
  • Treatment of any specific problems, such as joint stiffness (contractures), heart or breathing problems. There is a lot of research into MD at present and new treatments may be available in the future.[patient.info]
Seizure
  • Seizures have rarely been described in the pure forms while they seem to occur more frequently in complex forms. The aim of our study was to evaluate the incidence of seizure in CMD.[ncbi.nlm.nih.gov]
  • seizures (n   2), dilated cardiomyopathy (n   2), decreased left ventricular systolic function (n   2), congenital heart defects (n   3), sensorineural (n   1), and conductive hearing loss (n   1).[ncbi.nlm.nih.gov]
  • Seizures and respiratory complications occur in specific subtypes.[ncbi.nlm.nih.gov]
  • Seizures were controlled in a few weeks with intramuscular synthetic ACTH, followed by valproic acid. Two years later antiepileptic medication was withdrawn.[ncbi.nlm.nih.gov]
  • More than half of all affected children also experience seizures. Other signs and symptoms of Fukuyama congenital muscular dystrophy include impaired vision, other eye abnormalities, and slowly progressive heart problems after age 10.[ghr.nlm.nih.gov]
Nystagmus
  • Ocular abnormalities associated MEB disease include increased pressure within the eyes (infantile glaucoma), clouding of the lenses of the eyes (cataracts), rapid, involuntary eye movements (nystagmus), underdevelopment of the nerve-rich membrane lining[rarediseases.org]
  • Enlarged ventricles, brainstem hypoplasia and cerebellar hypoplasia are also very frequent.36,38 Ocular involvement is an invariable feature, ranging from severe myopia and retinal hypoplasia to congenital and infantile glaucoma, nystagmus, and cataract[healio.com]

Workup

Due to the heterogeneity of CMD and ongoing doubts regarding the genetic causes of certain types of the disease, anamnestic and clinical data remain essential for diagnosis. In detail, it is important to assess [1]:

Analyses of blood samples typically reveal slightly to markedly elevated levels of creatine kinase, but don't yield specific results that would allow for a reliable diagnosis. Highest concentrations of creatine kinase are measured in those suffering from CMD type 1A (primary merosin deficiency) or α-dystroglycanopathies (secondary merosin deficiency).

In order to provide a reliable diagnosis, histological examinations of muscle biopsy samples and genetic tests have to be realized. Magnetic resonance imaging of skeletal muscles is generally done before the decision on a certain biopsy site is taken. After performing the biopsy, immunohistochemical staining of muscle samples for glycosylated α-dystroglycan, laminin subunit α2, and collagen VI should be realized in order to distinguish the respective groups of CMD [3]. Microscopic examination of the native specimen usually reveals non-specific dystrophic changes of muscle fibers, e.g., fiber size variability, degeneration of muscle fibers, fibrosis, and lipomatosis [4]. Finally, molecular biological techniques are applied to identify the causal gene mutation. Because ultimately, genetic tests for CMD rely on multi-gene panels that include several genes associated with CMD, some authors state that muscle biopsies are no longer indispensable in cases where anamnestic and clinical data justify the tentative diagnosis of CMD [1].

Treatment

Causal treatment is not available and according to current knowledge, disease progression cannot be delayed pharmacologically. Thus, supportive therapy remains the only alternative. A multidisciplinary approach is required to improve a patient's quality of life. In this regard, tailor-made therapies are to be provided. They should be adapted to the individual patient's necessities and disease progression. In detail, affected individuals may need respiratory aids, non-invasive respiratory support, or mechanical ventilation. Orthopedic devices and physical therapy are often helpful to improve or maintain mobility, but surgical interventions may become necessary, too. Additionally, psychological support should be provided to CMD patients and their families.

Prognosis

The patient's prognosis largely depends on the type of CMD they are suffering from: Severe CMD is often early fatal, while individuals affected by mild CMD usually survive into adulthood and maintain a relatively good quality of life. In general, CMD follow a progressive course. Even though stagnation or even improvement may be noted in the short term, progressive weakness, limb-girdle muscle wasting, joint contractures and spinal deformities increasingly affect the patient's ability to cope with everyday life [1].

Etiology

CMD are genetic disorders that are mainly inherited in an autosomal recessive manner. Nevertheless, autosomal dominant inheritance may be observed, particularly in those suffering from collagen VI-related CMD. Thus, the recognition of a certain pattern of inheritance upon the analysis of a patient's pedigree may considerably shorten the list of differential diagnoses.

In any case, the tentative diagnosis of CMD should be confirmed by means of genetic analyses. To date, about 30 genes have been associated with CMD [3]. When interpreting sequencing results, it should be taken into account that certain types of CMD may be caused by mutations of different genes. On the other hand, mutations of one and the same gene may result in distinct types of CMD - a fact that further highlights the importance of a comprehensive workup and the consideration of anamnestic, clinical, and laboratory findings. Certain types of CMD, such as CMD type 1B, could not yet be related to specific mutations [5] and even if modern molecular biological techniques are applied, some patients still remain undiagnosed [3] [6] [7].

For a detailed listing of CMD and causative mutations, the interested reader is referred elsewhere [8].

Epidemiology

In Italy, the overall prevalence of CMD has been estimated to <1 in 100,000 inhabitants [6]. A total of 336 patients have been considered in the respective study and causative mutations have been identified in 220 cases. About 40% of all patients were found to suffer from CMD with abnormal glycosylation of α-dystroglycan, about 24% had CMD with merosin deficiency, and 20% were tested positive for Collagen VI-related CMD [6]. It should be noted, though, that incidence and prevalence of certain types of CMD vary considerably between distinct geographical regions. For instance, Fukuyama muscular dystrophy, a type of CMD with insufficient glycosylation of α-dystroglycan, is one of the most common autosomal recessive disorders in Japan, but is rarely diagnosed outside this country. Its incidence in Japan may be as high as 4 in 100,000 births [9].

Sex distribution
Age distribution

Pathophysiology

Dystrophin is a protein required for physiological muscle function. It is located within the sarcolemma, i.e., the membrane of striated muscle cells. It is part of the cytoskeleton and one of its main functions is to connect the muscle fiber's actin filaments with the plasma membrane. Dystrophin forms part of a multi-subunit-complex, the so-called dystrophin-associated glycoprotein complex. This complex constitutes a physical link between actin filaments and dystrophin on the inner side of the cell, and the basal lamina surrounding each muscle fiber. The majority of CMD-related genes encodes for proteins that are either part of the dystrophin-associated glycoprotein complex or affect its function. For instance, CMD type 1A is caused by mutations of the LAMA2 gene, which encodes for laminin subunit α2, which is expressed in the basement membrane, while the glycosylation of α-dystroglycan, a component of the dystrophin-associated glycoprotein complex and receptor for extracellular matrix protein, is disturbed in patients suffering from Fukuyama muscular dystrophy, muscle-eye-brain disease, or CMD types 1B, 1C, and 1D [2] [8] [10].

Prevention

Affected families may benefit from genetic counseling. Genetic analyses should be conducted to identify DNA sequence anomalies in any CMD patient and to clarify whom they were inherited from. On the other hand, such tests are very useful to check whether prospective parents related to an affected individual carry any of the mutations associated with CMD and whether their future child is at risk to develop such the disease. Ideally, these studies are realized before pregnancy. However, prenatal testing is also possible [1].

No recommendations can be given to prevent CMD provoked by de novo mutations.

Summary

CMD is a general term that refers to a heterogeneous group of diseases. Those disease have a few things in common, though: They are hereditary diseases that result from DNA sequence anomalies, symptoms are apparent at birth or manifest early in life, and affected individuals are at high risks of restrictive lung disease and orthopedic deformities [11].

Before genetic analyses became widely available, the diagnosis of CMD largely relied on the results of histological examinations of biopsy samples. Consequently, distinct types of CMD were classified according to pathohistological findings [12] [13]. Meanwhile, most CMD have been associated with certain genetic defects, and the classification system of CMD has repeatedly been revised [4]. Further updates are to be expected in the future. Currently, the term CMD does at least comprise the following disorders [8]:

  • CMD with abnormal glycosylation of α-dystroglycan, e.g. Fukuyama muscular dystrophy, muscle-eye-brain disease including Walker-Warburg syndrome, CMD type 1C, CMD type 1D
  • CMD with merosin deficiency (CMD type 1A)
  • Collagen VI-related CMD, including CMD type Ullrich and Bethlem myopathy, which are now considered to be a single entity
  • CMD with integrin deficiency
  • Other types of CMD, e.g., rigid spine syndrome, CMD with lamin A/C deficiency, CMD type 1B

Patient Information

Congenital muscular dystrophy (CMD) is a general term. It refers to distinct hereditary diseases characterized by early-onset hypotonia and muscle weakness as well as high risks of restrictive lung disease and orthopedic deformities. These disease are caused by mutations of genes that encode for proteins required for normal muscle function. First symptoms are usually apparent at birth, but may also manifest in infancy or childhood. In general, CMD follow a progressive course and cause increasing delays in motor development. Disease severity varies from patient to patient, though: Severe CMD may lead to early death, while those affected by milder forms of the disease may survive into adulthood and maintain a relatively good quality of life.

Besides progressive muscle wasting, the following may be noted in CMD patients:

The time of onset and distribution of orthopedic deformities, the involvement of the central nervous system, the eyes and the heart may provide valuable clues as to the type of CMD. Besides clinical data, the results of histological examinations of muscle biopsy samples and genetic tests are of major importance when establishing a diagnosis.

Unfortunately, causal treatment is not available and only supportive therapy can be provided. CMD patients benefit from a multidisciplinary approach to treatment that may involve physical therapy, orthopedic devices, surgical interventions, and respiratory support, among others.

References

Article

  1. Sparks SE, Quijano-Roy S, Harper A, et al. Congenital Muscular Dystrophy Overview. In: Adam MP, Ardinger HH, Pagon RA, et al., eds. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2017.
  2. Muntoni F, Torelli S, Brockington M. Muscular dystrophies due to glycosylation defects. Neurotherapeutics. 2008; 5(4):627-632.
  3. O'Grady GL, Lek M, Lamande SR, et al. Diagnosis and etiology of congenital muscular dystrophy: We are halfway there. Ann Neurol. 2016; 80(1):101-111.
  4. Falsaperla R, Praticò AD, Ruggieri M, et al. Congenital muscular dystrophy: from muscle to brain. Ital J Pediatr. 2016; 42(1):78.
  5. Brockington M, Sewry CA, Herrmann R, et al. Assignment of a form of congenital muscular dystrophy with secondary merosin deficiency to chromosome 1q42. Am J Hum Genet. 2000; 66(2):428-435.
  6. Graziano A, Bianco F, D'Amico A, et al. Prevalence of congenital muscular dystrophy in Italy: a population study. Neurology. 2015; 84(9):904-911.
  7. Ravenscroft G, Davis MR, Lamont P, Forrest A, Laing NG. New era in genetics of early-onset muscle disease: Breakthroughs and challenges. Semin Cell Dev Biol. 2017; 64:160-170.
  8. Reed UC. Congenital muscular dystrophy. Part I: a review of phenotypical and diagnostic aspects. Arq Neuropsiquiatr. 2009; 67(1):144-168.
  9. Saito K. Fukuyama Congenital Muscular Dystrophy. In: Adam MP, Ardinger HH, Pagon RA, et al., eds. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2017.
  10. Martin-Rendon E, Blake DJ. Protein glycosylation in disease: new insights into the congenital muscular dystrophies. Trends Pharmacol Sci. 2003; 24(4):178-183.
  11. Gilbreath HR, Castro D, Iannaccone ST. Congenital myopathies and muscular dystrophies. Neurol Clin. 2014; 32(3):689-703, viii.
  12. Kihira S, Nonaka I. Congenital muscular dystrophy. A histochemical study with morphometric analysis on biopsied muscles. J Neurol Sci. 1985; 70(2):139-149.
  13. McMenamin JB, Becker LE, Murphy EG. Congenital muscular dystrophy: a clinicopathologic report of 24 cases. J Pediatr. 1982; 100(5):692-697.

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Last updated: 2018-06-21 19:40