Phenotypes associated with the disease Synaptic congenital myasthenic syndrome (ORPHA:98915):
- Generalized muscle weakness (HP:0003324): Generalized weakness or decreased strength of the muscles, affecting both distal and proximal musculature. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:98915)
- 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: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:98915)
- Proximal muscle weakness (HP:0003701): A lack of strength of the proximal muscles. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:98915)
- Neck muscle weakness (HP:0000467): Decreased strength of the neck musculature. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Ophthalmoparesis (HP:0000597): Ophthalmoplegia is a paralysis or weakness of one or more of the muscles that control eye movement. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- 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. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Global developmental delay (HP:0001263): A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Bilateral ptosis (HP:0001488). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Weak cry (HP:0001612). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Dysphagia (HP:0002015): Difficulty in swallowing. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Poor suck (HP:0002033): An inadequate sucking reflex, resulting in the difficult of newborns to be breast-fed. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Respiratory insufficiency (HP:0002093). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Respiratory distress (HP:0002098): 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. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Distal muscle weakness (HP:0002460): Reduced strength of the musculature of the distal extremities. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Waddling gait (HP:0002515): Weakness of the hip girdle and upper thigh muscles, for instance in myopathies, leads to an instability of the pelvis on standing and walking. If the muscles extending the hip joint are affected, the posture in that joint becomes flexed and lumbar lordosis increases. The patients usually have difficulties standing up from a sitting position. Due to weakness in the gluteus medius muscle, the hip on the side of the swinging leg drops with each step (referred to as Trendelenburg sign). The gait appears waddling. The patients frequently attempt to counteract the dropping of the hip on the swinging side by bending the trunk towards the side which is in the stance phase (in the German language literature this is referred to as Duchenne sign). Similar gait patterns can be caused by orthopedic conditions when the origin and the insertion site of the gluteus medius muscle are closer to each other than normal, for instance due to a posttraumatic elevation of the trochanter or pseudarthrosis of the femoral neck. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Myopathy (HP:0003198): A disorder of muscle unrelated to impairment of innervation or neuromuscular junction. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Abnormal synaptic transmission at the neuromuscular junction (HP:0003398): Any abnormality of the neuromuscular junction, which is the synapse between the motor end plate of a motor neuron and the skeletal muscle fibers. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Prolonged miniature endplate currents (HP:0003436): An abnormal prolongation of the miniature endplate potentials, i.e. the postsynaptic response to transmitter released from an individual vesicle at the neuromuscular junction. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Decreased size of nerve terminals (HP:0003443): A reduction in the size of nerve terminals. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Scapular winging (HP:0003691): Abnormal protrusion of the scapula away from the surface of the back. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- 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. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Abnormal circulating enzyme concentration or activity (HP:0012379): Concentration or activity of an enzyme is above or below the limits of normal in the blood circulation. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- Unfavorable response of muscle weakness to acetylcholine esterase inhibitors (HP:0030203): Lack of improvement of muscle strength in response to administration of an acetylcholine esterase inhibitor. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:98915)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Intellectual disability (HP:0001249): The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Areflexia (HP:0001284): Absence of neurologic reflexes such as the knee-jerk reaction. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Neonatal respiratory distress (HP:0002643): Respiratory difficulty as newborn. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Scoliosis (HP:0002650): The presence of an abnormal lateral curvature of the spine. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Recurrent lower respiratory tract infections (HP:0002783): An increased susceptibility to lower respiratory tract infections as manifested by a history of recurrent lower respiratory tract infections. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Hypoventilation (HP:0002791): A reduction in the amount of air transported into the pulmonary alveoli by breathing, leading to hypercapnia (increase in the partial pressure of carbon dioxide). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Abnormality of the knee (HP:0002815): An abnormality of the knee joint or surrounding structures. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Skeletal muscle atrophy (HP:0003202): The presence of skeletal muscular atrophy (which is also known as amyotrophy). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Axial muscle weakness (HP:0003327): Reduced strength of the axial musculature (i.e., of the muscles of the head and neck, spine, and ribs). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Easy fatigability (HP:0003388): Increased susceptibility to fatigue. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Impaired mastication (HP:0005216): An abnormal reduction in the ability to masticate (chew), i.e., in the ability to crush and ground food in preparation for swallowing. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Limited extraocular movements (HP:0007941): Limited mobility of the eye within its socket. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Sleep apnea (HP:0010535): An intermittent cessation of airflow at the mouth and nose during sleep is known as sleep apnea. Apneas that last at least 10 seconds are considered significant, but individuals with sleep apnea may experience apneas lasting from 20 seconds up to 2 or 3 minutes. Patients may have up to 15 events per hour of sleep. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Slow pupillary light response (HP:0030211): Reduced velocity and acceleration in the pupillary light response. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:98915)
- Triangular mouth (HP:0000207): The presence of a triangular form of the mouth. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Mandibular prognathia (HP:0000303): Abnormal prominence of the chin related to increased length of the mandible. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Right ventricular hypertrophy (HP:0001667): In this case the right ventricle is more muscular than normal, causing a characteristic boot-shaped (coeur-en-sabot) appearance as seen on anterior- posterior chest x-rays. Right ventricular hypertrophy is commonly associated with any form of right ventricular outflow obstruction or pulmonary hypertension, which may in turn owe its origin to left-sided disease. The echocardiographic signs are thickening of the anterior right ventricular wall and the septum. Cavity size is usually normal, or slightly enlarged. In many cases there is associated volume overload present due to tricuspid regurgitation, in the absence of this, septal motion is normal. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Talipes equinovarus (HP:0001762): Talipes equinovarus (also called clubfoot) typically has four main components: inversion and adduction of the forefoot; inversion of the heel and hindfoot; equinus (limitation of extension) of the ankle and subtalar joint; and internal rotation of the leg. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Abnormal facial shape (HP:0001999): An abnormal morphology (form) of the face or its components. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Pulmonary arterial hypertension (HP:0002092): Pulmonary hypertension is defined mean pulmonary artery pressure of 25mmHg or more and pulmonary capillary wedge pressure of 15mmHg or less when measured by right heart catheterisation at rest and in a supine position. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Frequent falls (HP:0002359). Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Exertional dyspnea (HP:0002875): Perceived difficulty to breathe that occurs with exercise or exertion and improves with rest. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Type 2 muscle fiber atrophy (HP:0003554): Atrophy (wasting) affecting primary type 2 muscle fibers. This feature in general can only be observed on muscle biopsy. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Limited wrist extension (HP:0006251). Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)
- Hand muscle weakness (HP:0030237): Reduced strength of the musculature of the hand. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:98915)