- Retinoschisis (HP:0030502): Splitting of the neuroretinal layers of the retina. Evidence: PCS. Frequency: 2/4. (PMID:30635494)
- Juvenile onset (HP:0003621): Onset of signs or symptoms of disease between the age of 5 and 15 years. Evidence: PCS. Frequency: 1/4. (PMID:30635494)
- 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:610542)
- Ragged-red muscle fibers (HP:0003200): An abnormal appearance of muscle fibers observed on muscle biopsy. Ragged red fibers can be visualized with Gomori trichrome staining as irregular and intensely red subsarcolemmal zones, whereas the normal myofibrils are green. The margins of affect fibers appear red and ragged. The ragged-red is due to the accumulation of abnormal mitochondria below the plasma membrane of the muscle fiber, leading to the appearance of a red rim and speckled sarcoplasm. Evidence: PCS. Frequency: 2/2. (PMID:30635494)
- Easy fatigability (HP:0003388): Increased susceptibility to fatigue. Evidence: IEA. (OMIM:610542)
- 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: IEA. (OMIM:610542)
- Muscle spasm (HP:0003394): Sudden and involuntary contractions of one or more muscles. Evidence: IEA. (OMIM:610542)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: PCS. Frequency: 4/4. (PMID:30635494)
- Gowers sign (HP:0003391): A phenomenon whereby patients are not able to stand up without the use of the hands owing to weakness of the proximal muscles of the lower limbs. Evidence: IEA. (OMIM:610542)
- Mildly elevated creatine kinase (HP:0008180). Evidence: IEA. (OMIM:610542)
- Childhood onset (HP:0011463): Onset of disease at the age of between 1 and 5 years. Evidence: PCS. Frequency: 1/4. (PMID:30635494)
- 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: IEA. (OMIM:610542)
- Autosomal recessive inheritance (HP:0000007): 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 individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele). Evidence: PCS. (PMID:21310273)
- 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: PCS. Frequency: 2/4. (PMID:30635494)
- Proximal amyotrophy (HP:0007126): Amyotrophy (muscular atrophy) affecting the proximal musculature. Evidence: TAS. (OMIM:610542)
- Proximal muscle weakness (HP:0003701): A lack of strength of the proximal muscles. Evidence: PCS. Frequency: 4/4. (PMID:30635494)
- Ophthalmoparesis (HP:0000597): Ophthalmoplegia is a paralysis or weakness of one or more of the muscles that control eye movement. Evidence: IEA. (OMIM:610542)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 2/4. (PMID:30635494)
- Neck muscle weakness (HP:0000467): Decreased strength of the neck musculature. Evidence: TAS. (OMIM:610542)
- 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: 2/2. (PMID:30635494)
These phenotypes are associated with the disease congenital myasthenic syndrome 12 (OMIM:610542).