Phenotypes associated with the disease congenital myasthenic syndrome 2A (OMIM:616313):
- Poor head control (HP:0002421): Difficulty to maintain correct position of the head while standing or sitting. Infant head lag is observed when the head seems to flop around or lags posteriorly behind the trunk. Several articles have maintained that head lag should be absent by age 3 to 4 months. Evidence: PCS. Frequency: 1/1. Onset: Infantile onset (HP:0003593). (PMID:8651643)
- Facial palsy (HP:0010628): Facial nerve palsy is a dysfunction of cranial nerve VII (the facial nerve) that results in inability to control facial muscles on the affected side with weakness of the muscles of facial expression and eye closure. This can either be present in unilateral or bilateral form. Evidence: TAS. (OMIM:616313)
- Congenital onset (HP:0003577): A phenotypic abnormality that is present at birth. Evidence: TAS. Frequency: 1/1. (OMIM:616313)
- Muscle fiber splitting (HP:0003555): Fiber splitting or branching is a common finding in human and rat skeletal muscle pathology. Fiber splitting refers to longitudinal halving of the complete fiber, while branching originates from a regenerating end of a necrotic fiber as invaginations of the sarcolemma. In fiber branching, one end of the fiber remains intact as a single entity, while the other end has several branches. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Myopathy (HP:0003198): A disorder of muscle unrelated to impairment of innervation or neuromuscular junction. Evidence: PCS. (PMID:8651643)
- Flexion contracture (HP:0001371): A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. It is thus a chronic loss of joint motion due to structural changes in muscle, tendons, ligaments, or skin that prevents normal movement of joints. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Fatigable weakness (HP:0003473): A type of weakness that occurs after a muscle group is used and lessens if the muscle group has some rest. That is, there is diminution of strength with repetitive muscle actions. Evidence: PCS. Frequency: 1/1. Onset: Congenital onset (HP:0003577). (PMID:8872460)
- Hypotonia (HP:0001252): 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. Evidence: TAS. Onset: Neonatal onset (HP:0003623). (OMIM:616313)
- Limb muscle weakness (HP:0003690): Reduced strength and weakness of the muscles of the arms and legs. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- High palate (HP:0000218): 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). Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Delayed ability to sit (HP:0025336): A failure to achieve the ability to sit at an appropriate developmental stage. Most children sit with support at 6 months of age and sit steadily without support at 9 months of age. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Type 1 muscle fiber predominance (HP:0003803): An abnormal predominance of type I muscle fibers (in general, this feature can only be observed on muscle biopsy). Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Abnormally high-pitched voice (HP:0001620): A persistent (minutes to hours) abnormal increase in the pitch (frequency) of the voice for the context or social situation or significantly different from baseline of the individual. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- EMG: decremental response of compound muscle action potential to repetitive nerve stimulation (HP:0003403): A compound muscle action potential (CMAP) is a type of electromyography (EMG). CMAP refers to a group of almost simultaneous action potentials from several muscle fibers in the same area evoked by stimulation of the supplying motor nerve and are recorded as one multipeaked summated action potential. This abnormality refers to a greater than normal decrease in the amplitude during the course of the investigation. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Skeletal muscle atrophy (HP:0003202): The presence of skeletal muscular atrophy (which is also known as amyotrophy). Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Narrow face (HP:0000275): 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). Evidence: TAS. (OMIM:616313)
- Long face (HP:0000276): 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). Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Easy fatigability (HP:0003388): Increased susceptibility to fatigue. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Delayed ability to walk (HP:0031936): A failure to achieve the ability to walk at an appropriate developmental stage. Most children learn to walk in a series of stages, and learn to walk short distances independently between 12 and 15 months. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Poor suck (HP:0002033): An inadequate sucking reflex, resulting in the difficult of newborns to be breast-fed. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Anti-neuromuscular Junction acetylcholine receptor antibody positivity (HP:0030208): The presence of autoantibodies (immunoglobulins) in the blood circulation that react against neuromuscular junction acetylcholine receptors. Evidence: PCS. Frequency: 0/2. (PMID:8872460;PMID:8651643)
- Knee flexion contracture (HP:0006380): A type of knee joint contracture in which the knee is in a fixed bent (flexed) configuration such that it cannot be straightened actively or passively. Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Ptosis (HP:0000508): The upper eyelid margin is positioned 3 mm or more lower than usual and covers the superior portion of the iris (objective); or, the upper lid margin obscures at least part of the pupil (subjective). Evidence: PCS. Frequency: 1/1. (PMID:8651643)
- Ophthalmoplegia (HP:0000602): Paralysis of one or more extraocular muscles that are responsible for eye movements. Evidence: PCS. Frequency: 1/1. Onset: Juvenile onset (HP:0003621). (PMID:8651643)
- Neonatal hypotonia (HP:0001319): Muscular hypotonia (abnormally low muscle tone) manifesting in the neonatal period. Evidence: TAS. (OMIM:616313)
- Autosomal dominant inheritance (HP:0000006): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele. Evidence: PCS. (PMID:8872460)
- Increased variability in muscle fiber diameter (HP:0003557): An abnormally high degree of muscle fiber size variation. This phenotypic feature can be observed upon muscle biopsy. Evidence: PCS. Frequency: 1/1. (PMID:8651643)