Phenotypes associated with the disease spinal muscular atrophy, type IV (OMIM:271150):
- EMG: neuropathic changes (HP:0003445): The presence of characteristic findings of denervation on electromyography (fibrillations, positive sharp waves, and giant motor unit potentials). Evidence: IEA. (OMIM:271150)
- Hand tremor (HP:0002378): An unintentional, oscillating to-and-fro muscle movement affecting the hand. Evidence: PCS. Frequency: 5/6. (PMID:7658877)
- Centrally nucleated skeletal muscle fibers (HP:0003687): 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). Evidence: PCS. Frequency: 1/1. (PMID:7658877)
- Degeneration of anterior horn cells (HP:0002398). Evidence: IEA. (OMIM:271150)
- Quadriceps muscle atrophy (HP:0009050): Muscular atrophy involving the quadriceps muscle. Evidence: PCS. Frequency: 5/6. (PMID:7658877)
- Angulated muscle fibers (HP:0034045): Normal muscle fibers are polygonal-shaped in cross section, are multinucleated, and have minimal amounts of endomysial connective tissue. In contrast, angulated (also known as angular) muscle fibers have long and narrow vertices (corners) with sharp edges and a pointed tip. Evidence: PCS. Frequency: 1/1. (PMID:7658877)
- Young adult onset (HP:0011462): Onset of disease at the age of between 16 and 40 years. Evidence: PCS. Frequency: 6/6. (PMID:7658877)
- Calf muscle hypertrophy (HP:0008981): Muscle hypertrophy affecting the calf muscles. Evidence: PCS. Frequency: 3/6. (PMID:7658877)
- 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:7658877)
- Rimmed vacuoles (HP:0003805): Presence of abnormal vacuoles (membrane-bound organelles) in the sarcolemma. On histological staining with hematoxylin and eosin, rimmed vacuoles are popcorn-like clear vacuoles with a densely blue rim. The vacuoles are often associated with cytoplasmic and occasionally intranuclear eosinophilic inclusions. Evidence: PCS. Frequency: 1/1. (PMID:7658877)
- Tongue fasciculations (HP:0001308): Fasciculations or fibrillation affecting the tongue muscle. Evidence: PCS. Frequency: 5/6. (PMID:7658877)
- 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: 3/6. (PMID:7658877)
- Proximal amyotrophy (HP:0007126): Amyotrophy (muscular atrophy) affecting the proximal musculature. Evidence: IEA. (OMIM:271150)
- Spinal muscular atrophy (HP:0007269): Muscular weakness and atrophy related to loss of the motor neurons of the spinal cord and brainstem. Evidence: PCS. (PMID:7658877)
- 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:7658877)
- Proximal muscle weakness (HP:0003701): A lack of strength of the proximal muscles. Evidence: PCS. Frequency: 6/6. (PMID:7658877)
- Muscle fiber necrosis (HP:0003713): Abnormal cell death involving muscle fibers usually associated with break in, or absence of, muscle surface fiber membrane and resulting in irreversible damage to muscle fibers. Evidence: PCS. Frequency: 1/1. (PMID:7658877)
- Areflexia of lower limbs (HP:0002522): Inability to elicit tendon reflexes in the lower limbs. Evidence: IEA. (OMIM:271150)
- Slowly progressive (HP:0003677): Applies to a disease manifestation that only slowly increases in scope or severity over the course of time. Evidence: PCS. (PMID:7658877)
- 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:7658877)