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Congenital myopathy 2c, severe infantile, autosomal dominant(CMYP2C)

MedGen UID:
1840969
Concept ID:
C5830333
Disease or Syndrome
Synonyms: CMYP2C; CONGENITAL MYOPATHY 2C, SEVERE INFANTILE, AUTOSOMAL DOMINANT
 
Gene (location): ACTA1 (1q42.13)
 
Monarch Initiative: MONDO:0859523
OMIM®: 620278

Definition

Congenital myopathy-2C (CMYP2C) is an autosomal dominant disorder of the skeletal muscle characterized by severe congenital weakness usually resulting in death from respiratory failure in the first year or so of life. Patients present at birth with hypotonia, lack of antigravity movements, poor head control, and difficulties feeding or breathing, often requiring tube-feeding and mechanical ventilation. Decreased fetal movements may be observed in some cases. Of the patients with congenital myopathy caused by mutation in the ACTA1 gene, about 90% carry heterozygous mutations that are usually de novo and cause the severe infantile phenotype. Some patients with heterozygous mutations have a more typical and milder disease course with delayed motor development and proximal muscle weakness, but are able to achieve independent ambulation (CMYP2A; 161800). The severity of the disease most likely depends on the detrimental effect of the mutation, although there are probably additional modifying factors (Ryan et al., 2001; Laing et al., 2009; Sanoudou and Beggs, 2001; Agrawal et al., 2004; Nowak et al., 2013; Sewry et al., 2019; Laitila and Wallgren-Pettersson, 2021). For a discussion of genetic heterogeneity of congenital myopathy, see CMYP1A (117000). [from OMIM]

Clinical features

From HPO
Knee contracture
MedGen UID:
332406
Concept ID:
C1837263
Anatomical Abnormality
Lack of full passive range of motion (restrictions in flexion, extension, or other movements) of the knee joint resulting from structural changes of non-bony tissues, such as muscles, tendons, ligaments, joint capsules and/or skin.
Subdural hemorrhage
MedGen UID:
6775
Concept ID:
C0018946
Pathologic Function
Hemorrhage occurring between the dura mater and the arachnoid mater.
Cerebral hemorrhage
MedGen UID:
423648
Concept ID:
C2937358
Pathologic Function
Hemorrhage into the parenchyma of the brain.
Dysphagia
MedGen UID:
41440
Concept ID:
C0011168
Disease or Syndrome
Difficulty in swallowing.
Tube feeding
MedGen UID:
8641
Concept ID:
C0014327
Therapeutic or Preventive Procedure
Feeding problem necessitating food and nutrient delivery via a tube.
Feeding difficulties
MedGen UID:
65429
Concept ID:
C0232466
Finding
Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it.
Nasogastric tube feeding
MedGen UID:
847783
Concept ID:
C3853581
Medical Device
The condition of inability to eat normally treated by placement of a thin tube through the nose into the stomach that is then used to carry food.
Gastrostomy tube feeding in infancy
MedGen UID:
892362
Concept ID:
C4023342
Finding
Feeding problem necessitating gastrostomy tube feeding.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Motor delay
MedGen UID:
381392
Concept ID:
C1854301
Finding
A type of Developmental delay characterized by a delay in acquiring motor skills.
Delayed ability to roll over
MedGen UID:
1718874
Concept ID:
C5397980
Finding
Delayed achievement of the ability to roll front to back and back to front.
Joint contracture
MedGen UID:
3228
Concept ID:
C0009918
Anatomical Abnormality
A limitation in the passive range of motion of a joint resulting from loss of elasticity in the periarticular tissues owing to structural changes of non-bony tissues, such as muscles, tendons, ligaments, joint capsules or skin. A contracture prevents movement of the associated body part.
Hypotonia
MedGen UID:
10133
Concept ID:
C0026827
Finding
Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.
Joint contracture of the hand
MedGen UID:
56382
Concept ID:
C0158113
Finding
Contractures of one ore more joints of the hands meaning chronic loss of joint motion due to structural changes in non-bony tissue.
Weakness of facial musculature
MedGen UID:
98103
Concept ID:
C0427055
Disease or Syndrome
Reduced strength of one or more muscles innervated by the facial nerve (the seventh cranial nerve).
Muscular atrophy
MedGen UID:
892680
Concept ID:
C0541794
Pathologic Function
The presence of skeletal muscular atrophy (which is also known as amyotrophy).
Generalized muscle weakness
MedGen UID:
155433
Concept ID:
C0746674
Sign or Symptom
Generalized weakness or decreased strength of the muscles, affecting both distal and 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
Nemaline bodies
MedGen UID:
814369
Concept ID:
C3808039
Finding
Nemaline rods are abnormal bodies that can occur in skeletal muscle fibers. The rods can be observed on histological analysis of muscle biopsy tissue or upon electron microscopy, where they appear either as extensions of sarcomeric Z-lines, in random array without obvious attachment to Z-lines (often in areas devoid of sarcomeres) or in large clusters localized at the sarcolemma or intermyofibrillar spaces.
Increased endomysial connective tissue
MedGen UID:
867771
Concept ID:
C4022161
Finding
An increased volume of the endomysium, which is a connective tissue sheath that surrounds each muscule fiber. Together, bundles of muscle fibers form a fasciculus, surrounded by another layer of connective tissue called the perimysium.
Abnormality of skeletal muscle fiber size
MedGen UID:
868650
Concept ID:
C4023051
Anatomical Abnormality
Any abnormality of the size of the skeletal muscle cell.
Chylothorax
MedGen UID:
40305
Concept ID:
C0008733
Disease or Syndrome
Accumulation of excessive amounts of lymphatic fluid (chyle) in the pleural cavity.
Respiratory distress
MedGen UID:
96907
Concept ID:
C0476273
Sign or Symptom
Respiratory distress is objectively observable as the physical or emotional consequences from the experience of dyspnea. The physical presentation of respiratory distress is generally referred to as labored breathing, while the sensation of respiratory distress is called shortness of breath or dyspnea.
Respiratory failure
MedGen UID:
257837
Concept ID:
C1145670
Disease or Syndrome
A severe form of respiratory insufficiency characterized by inadequate gas exchange such that the levels of oxygen or carbon dioxide cannot be maintained within normal limits.
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).
Mandibular prognathia
MedGen UID:
98316
Concept ID:
C0399526
Finding
Abnormal prominence of the chin related to increased length of the mandible.
Mask-like facies
MedGen UID:
140860
Concept ID:
C0424448
Finding
A lack of facial expression often with staring eyes and a slightly open mouth.
Long face
MedGen UID:
324419
Concept ID:
C1836047
Finding
Facial height (length) is more than 2 standard deviations above the mean (objective); or, an apparent increase in the height (length) of the face (subjective).
Narrow face
MedGen UID:
373334
Concept ID:
C1837463
Finding
Bizygomatic (upper face) and bigonial (lower face) width are both more than 2 standard deviations below the mean (objective); or, an apparent reduction in the width of the upper and lower face (subjective).
Breech presentation
MedGen UID:
654
Concept ID:
C0006157
Pathologic Function
A position of the fetus at delivery in which the fetus enters the birth canal with the buttocks or feet first.
Decreased fetal movement
MedGen UID:
68618
Concept ID:
C0235659
Finding
An abnormal reduction in quantity or strength of fetal movements.

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