- Skeletal muscle atrophy (HP:0003202): The presence of skeletal muscular atrophy (which is also known as amyotrophy). Evidence: TAS. (OMIM:611105)
- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: TAS. (OMIM:611105)
- Peripheral axonal neuropathy (HP:0003477): An abnormality characterized by disruption of the normal functioning of peripheral axons. Evidence: TAS. (OMIM:611105)
- Babinski sign (HP:0003487): 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: TAS. (OMIM:611105)
- Flexion contracture (HP:0001371): A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. It is thus a chronic loss of joint motion due to structural changes in muscle, tendons, ligaments, or skin that prevents normal movement of joints. Evidence: TAS. (OMIM:611105)
- Dysarthria (HP:0001260): Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed. Evidence: TAS. Frequency: Occasional (HP:0040283). (OMIM:611105)
- Leukoencephalopathy (HP:0002352): This term describes abnormality of the white matter of the cerebrum resulting from damage to the myelin sheaths of nerve cells. Evidence: TAS. (OMIM:611105)
- Ataxia (HP:0001251): Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly). Evidence: TAS. (OMIM:611105)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: TAS. (OMIM:611105)
- Cognitive impairment (HP:0100543): Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering. Evidence: TAS. Frequency: Occasional (HP:0040283). (OMIM:611105)
- Nystagmus (HP:0000639): Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms. Evidence: TAS. (OMIM:611105)
- Variable expressivity (HP:0003828): A variable severity of phenotypic features. Evidence: TAS. (OMIM:611105)
- 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: TAS. (OMIM:611105)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: TAS. (OMIM:611105)
- Spasticity (HP:0001257): A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes. Evidence: TAS. (OMIM:611105)
- Slowly progressive (HP:0003677): Applies to a disease manifestation that only slowly increases in scope or severity over the course of time. Evidence: TAS. (OMIM:611105)
- Tremor (HP:0001337): An unintentional, oscillating to-and-fro muscle movement about a joint axis. Evidence: TAS. (OMIM:611105)
- Hyperreflexia (HP:0001347): Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles. Evidence: TAS. (OMIM:611105)
These phenotypes are associated with the disease leukoencephalopathy with brain stem and spinal cord involvement-high lactate syndrome (OMIM:611105).