- Hyporeflexia (HP:0001265, a Human Phenotype Ontology term): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: IEA. (OMIM:300489)
- EMG: neuropathic changes (HP:0003445, a Human Phenotype Ontology term): The presence of characteristic findings of denervation on electromyography (fibrillations, positive sharp waves, and giant motor unit potentials). Evidence: IEA. (OMIM:300489)
- Juvenile onset (HP:0003621, a Human Phenotype Ontology term): Onset of signs or symptoms of disease between the age of 5 and 15 years. Evidence: IEA. (OMIM:300489)
- Pes cavus (HP:0001761, a Human Phenotype Ontology term): An increase in height of the medial longitudinal arch of the foot that does not flatten on weight bearing (i.e., a distinctly hollow form of the sole of the foot when it is bearing weight). Evidence: IEA. (OMIM:300489)
- Distal amyotrophy (HP:0003693, a Human Phenotype Ontology term): Muscular atrophy affecting muscles in the distal portions of the extremities. Evidence: IEA. (OMIM:300489)
- Abnormal peripheral nervous system morphology (HP:0000759, a Human Phenotype Ontology term): A structural abnormality of the peripheral nervous system, which is composed of the nerves that lead to or branch off from the central nervous system. This includes the cranial nerves (olfactory and optic nerves are technically part of the central nervous system). Evidence: TAS. (OMIM:300489)
- X-linked recessive inheritance (HP:0001419, a Human Phenotype Ontology term): A mode of inheritance that is observed for recessive traits related to a gene encoded on the X chromosome. In the context of medical genetics, X-linked recessive disorders manifest in males (who have one copy of the X chromosome and are thus hemizygotes), but generally not in female heterozygotes who have one mutant and one normal allele. Evidence: IEA. (OMIM:300489)
- Distal muscle weakness (HP:0002460, a Human Phenotype Ontology term): Reduced strength of the musculature of the distal extremities. Evidence: IEA. (OMIM:300489)
- Distal sensory impairment (HP:0002936, a Human Phenotype Ontology term): An abnormal reduction in sensation in the distal portions of the extremities. Evidence: IEA. Frequency: Occasional (HP:0040283, a Human Phenotype Ontology term). (OMIM:300489)
- Unsteady gait (HP:0002317, a Human Phenotype Ontology term). Evidence: IEA. (OMIM:300489)
- Spinal muscular atrophy (HP:0007269, a Human Phenotype Ontology term): Muscular weakness and atrophy related to loss of the motor neurons of the spinal cord and brainstem. Evidence: TAS. (OMIM:300489)
- Slowly progressive (HP:0003677, a Human Phenotype Ontology term): Applies to a disease manifestation that only slowly increases in scope or severity over the course of time. Evidence: IEA. (OMIM:300489)
These phenotypes are associated with the disease X-linked distal spinal muscular atrophy type 3 (OMIM:300489, an entry in Online Mendelian Inheritance in Man).