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Myopathy, myosin storage, autosomal recessive(CMYO7B)

MedGen UID:
340603
Concept ID:
C1850709
Disease or Syndrome
Synonyms: CMYO7B; CONGENITAL MYOPATHY 7B, MYOSIN STORAGE, AUTOSOMAL RECESSIVE
 
Gene (location): MYH7 (14q11.2)
 
Monarch Initiative: MONDO:0009708
OMIM®: 255160

Definition

Autosomal recessive myosin storage congenital myopathy-7B (CMYO7B) is a skeletal muscle disorder characterized by the onset of scapuloperoneal muscle weakness in early childhood or young adulthood. Affected individuals have difficulty walking, steppage gait, and scapular winging due to shoulder girdle involvement. The severity and progression of the disorder is highly variable, even within families. Most patients develop respiratory insufficiency, nocturnal hypoventilation, and restrictive lung disease; some develop hypertrophic cardiomyopathy. Additional features include myopathic facies, high-arched palate, scoliosis, and muscle wasting with thin body habitus. Serum creatine kinase may be normal or elevated. Skeletal muscle biopsy shows variable findings, including myosin storage disease, type 1 fiber predominance, centralized nuclei, and multiminicore disease (Onengut et al., 2004; Tajsharghi et al., 2007; Beecroft et al., 2019). For a discussion of genetic heterogeneity of congenital myopathy, see CMYO1A (117000). [from OMIM]

Clinical features

From HPO
Limb-girdle muscle weakness
MedGen UID:
347625
Concept ID:
C1858127
Finding
Weakness of the limb-girdle muscles (also known as the pelvic and shoulder girdles), that is, lack of strength of the muscles around the shoulders and the pelvis.
Primary dilated cardiomyopathy
MedGen UID:
2880
Concept ID:
C0007193
Disease or Syndrome
Familial dilated cardiomyopathy is a genetic form of heart disease. It occurs when heart (cardiac) muscle becomes thin and weakened in at least one chamber of the heart, causing the open area of the chamber to become enlarged (dilated). As a result, the heart is unable to pump blood as efficiently as usual. To compensate, the heart attempts to increase the amount of blood being pumped through the heart, leading to further thinning and weakening of the cardiac muscle. Over time, this condition results in heart failure.\n\nIt usually takes many years for symptoms of familial dilated cardiomyopathy to cause health problems. They typically begin in mid-adulthood, but can occur at any time from infancy to late adulthood. Signs and symptoms of familial dilated cardiomyopathy can include an irregular heartbeat (arrhythmia), shortness of breath (dyspnea), extreme tiredness (fatigue), fainting episodes (syncope), and swelling of the legs and feet. In some cases, the first sign of the disorder is sudden cardiac death. The severity of the condition varies among affected individuals, even in members of the same family.
Hypertrophic cardiomyopathy
MedGen UID:
2881
Concept ID:
C0007194
Disease or Syndrome
Hypertrophic cardiomyopathy (HCM) is defined by the presence of increased ventricular wall thickness or mass in the absence of loading conditions (hypertension, valve disease) sufficient to cause the observed abnormality.
Congestive heart failure
MedGen UID:
9169
Concept ID:
C0018802
Disease or Syndrome
The presence of an abnormality of cardiac function that is responsible for the failure of the heart to pump blood at a rate that is commensurate with the needs of the tissues or a state in which abnormally elevated filling pressures are required for the heart to do so. Heart failure is frequently related to a defect in myocardial contraction.
Sinus tachycardia
MedGen UID:
11700
Concept ID:
C0039239
Disease or Syndrome
Heart rate of greater than 100 beats per minute.
Right bundle branch block
MedGen UID:
88445
Concept ID:
C0085615
Disease or Syndrome
A conduction block of the right branch of the bundle of His. This manifests as a prolongation of the QRS complex (greater than 0.12 s) with delayed activation of the right ventricle and terminal delay on the EKG.
Right axis deviation
MedGen UID:
534422
Concept ID:
C0232296
Finding
A kind of abnormal ventricular axis in the EKG whereby the QRS axis falls between +90 degrees and 180 degrees, or beyond +100 degrees if the adult range is used.
Biventricular hypertrophy
MedGen UID:
807328
Concept ID:
C0281788
Disease or Syndrome
Thickening of the heart walls in both ventricles.
Fourth heart sound
MedGen UID:
604154
Concept ID:
C0425593
Finding
The fourth heart sound (S4) is a low-pitched sound that occurs just before the first heart sound (S1) when the atria contract to force blood into the left ventricle, that is, coincident with late diastolic filling of the ventricle due to atrial contraction.
Elevated jugular venous pressure
MedGen UID:
636282
Concept ID:
C0520861
Finding
Increased jugular venous pressure.
Short stature
MedGen UID:
87607
Concept ID:
C0349588
Finding
A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).
Loss of ambulation
MedGen UID:
332305
Concept ID:
C1836843
Finding
Inability to walk in a person who previous had the ability to walk.
Scoliosis
MedGen UID:
11348
Concept ID:
C0036439
Disease or Syndrome
The presence of an abnormal lateral curvature of the spine.
Muscle weakness
MedGen UID:
57735
Concept ID:
C0151786
Finding
Reduced strength of muscles.
Proximal muscle weakness
MedGen UID:
113169
Concept ID:
C0221629
Finding
A lack of strength of the proximal muscles.
Scapuloperoneal weakness
MedGen UID:
331234
Concept ID:
C1842161
Finding
Scapuloperoneal amyotrophy
MedGen UID:
331235
Concept ID:
C1842162
Finding
Muscular atrophy in the distribution of shoulder girdle and peroneal muscles.
Centrally nucleated skeletal muscle fibers
MedGen UID:
330782
Concept ID:
C1842170
Finding
An abnormality in which the nuclei of sarcomeres take on an abnormally central localization (or in which this feature is found in an increased proportion of muscle cells).
Calf muscle hypertrophy
MedGen UID:
335868
Concept ID:
C1843057
Finding
Muscle hypertrophy affecting the calf muscles.
Proximal amyotrophy
MedGen UID:
342591
Concept ID:
C1850794
Disease or Syndrome
Amyotrophy (muscular atrophy) affecting the proximal musculature.
Type 1 muscle fiber predominance
MedGen UID:
344274
Concept ID:
C1854387
Finding
An abnormal predominance of type I muscle fibers (in general, this feature can only be observed on muscle biopsy).
Thoracic scoliosis
MedGen UID:
387910
Concept ID:
C1857790
Anatomical Abnormality
EMG: myopathic abnormalities
MedGen UID:
867362
Concept ID:
C4021726
Pathologic Function
The presence of abnormal electromyographic patterns indicative of myopathy, such as small-short polyphasic motor unit potentials.
Muscle fiber hyaline bodies
MedGen UID:
867765
Concept ID:
C4022155
Anatomical Abnormality
Subsarcolemmal, eosinophilic glass-like regions in the cytoplasm of muscle fibers. Hyaline bodies show significant reactivity to myofibrillar ATPase after acid pre-incubation and with immunohistochemistry, show intense reactivity with only slow myosin heavy chain. Electron microscopy of the affected areas show a lack of myofibrils and a uniform, finely granular matrix, sometimes suggesting a filamentous nature, containing few scattered nuclei and mitochondria.
Respiratory insufficiency
MedGen UID:
11197
Concept ID:
C0035229
Pathologic Function
Impairment of gas exchange within the lungs secondary to a disease process, neoplasm, or trauma, possibly resulting in hypoxia, hypercarbia, or both, but not requiring intubation or mechanical ventilation. Patients are normally managed with pharmaceutical therapy, supplemental oxygen, or both.
Exertional dyspnea
MedGen UID:
68549
Concept ID:
C0231807
Sign or Symptom
Perceived difficulty to breathe that occurs with exercise or exertion and improves with rest.
Restrictive ventilatory defect
MedGen UID:
478856
Concept ID:
C3277226
Finding
A functional defect characterized by reduced total lung capacity (TLC) not associated with abnormalities of expiratory airflow or airway resistance. Spirometrically, a restrictive defect is defined as FEV1 (forced expiratory volume in 1 second) and FVC (forced vital capacity) less than 80 per cent. Restrictive lung disease may be caused by alterations in lung parenchyma or because of a disease of the pleura, chest wall, or neuromuscular apparatus.
Elevated circulating creatine kinase concentration
MedGen UID:
69128
Concept ID:
C0241005
Finding
An elevation of the level of the enzyme creatine kinase (also known as creatine phosphokinase (CK; EC 2.7.3.2) in the blood. CK levels can be elevated in a number of clinical disorders such as myocardial infarction, rhabdomyolysis, and muscular dystrophy.
High palate
MedGen UID:
66814
Concept ID:
C0240635
Congenital Abnormality
Height of the palate more than 2 SD above the mean (objective) or palatal height at the level of the first permanent molar more than twice the height of the teeth (subjective).
Myopathic facies
MedGen UID:
90695
Concept ID:
C0332615
Finding
A facial appearance characteristic of myopathic conditions. The face appears expressionless with sunken cheeks, bilateral ptosis, and inability to elevate the corners of the mouth, due to muscle weakness.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  

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