- Clonus (HP:0002169, a Human Phenotype Ontology term): A series of rhythmic and involuntary muscle contractions (at a frequency of about 5 to 7 Hz) that occur in response to an abruptly applied and sustained stretch. Evidence: IEA. (OMIM:300750)
- Babinski sign (HP:0003487, a Human Phenotype Ontology term): Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract. Evidence: IEA. (OMIM:300750)
- Impaired vibratory sensation (HP:0002495, a Human Phenotype Ontology term): A decrease in the ability to perceive vibration. Clinically, this is usually tested with a tuning fork which vibrates at 128 Hz and is applied to bony prominences such as the malleoli at the ankles or the metacarpal-phalangeal joints. There is a slow decay of vibration from the tuning fork. The degree of vibratory sense loss can be crudely estimated by counting the number of seconds that the examiner can perceive the vibration longer than the patient. Evidence: IEA. (OMIM:300750)
- Paraplegia (HP:0010550, a Human Phenotype Ontology term): Severe or complete weakness of both lower extremities with sparing of the upper extremities. Evidence: IEA. (OMIM:300750)
- 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: TAS. (OMIM:300750)
- Spastic gait (HP:0002064, a Human Phenotype Ontology term): Spasticity is manifested by increased stretch reflex which is intensified with movement velocity. This results in excessive and inappropriate muscle activation which can contribute to muscle hypertonia. Spastic gait is characterized by manifestations such as muscle hypertonia, stiff knee, and circumduction of the leg. Evidence: IEA. (OMIM:300750)
- Spastic paraplegia (HP:0001258, a Human Phenotype Ontology term): Complete loss of the ability to move the lower limbs accompanied by spasticity of the lower limbs. Evidence: IEA. (OMIM:300750)
- 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:300750)
- Hyperreflexia (HP:0001347, a Human Phenotype Ontology term): Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles. Evidence: IEA. (OMIM:300750)
These phenotypes are associated with the disease hereditary spastic paraplegia 34 (OMIM:300750, an entry in Online Mendelian Inheritance in Man).