- Undetectable electroretinogram (HP:0000550): Lack of any response to stimulation upon electroretinography. Evidence: IEA. (OMIM:204500)
- Reduced tissue tripeptidyl peptidase 1 activity (HP:6000571): Activity of tripeptidyl peptidase 1 (TPP1;EC 3.4.14.9) in the tissues below the lower limit of normal. TTP1 activity can be measured in tissues including fibroblasts and leukocytes muscle. Evidence: PCS. Frequency: 2/2. (PMID:37922835)
- Cerebral atrophy (HP:0002059): Atrophy (wasting, decrease in size of cells or tissue) affecting the cerebrum. Evidence: IEA. (OMIM:204500)
- Delayed speech and language development (HP:0000750): A degree of language development that is significantly below the norm for a child of a specified age. Evidence: IEA. (OMIM:204500)
- Abnormal nervous system electrophysiology (HP:0001311): An abnormality of the function of the electrical signals with which nerve cells communicate with each other or with muscles as measured by electrophysiological investigations. Evidence: IEA. (OMIM:204500)
- Developmental regression (HP:0002376): Loss of developmental skills, as manifested by loss of developmental milestones. Evidence: IEA. (OMIM:204500)
- Seizure (HP:0001250): A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Evidence: IEA. (OMIM:204500)
- Increased extraneuronal autofluorescent lipopigment (HP:0003463): Lipofuscin, a generic term applied to autofluorescent lipopigment, is a mixture of protein and lipid that accumulates in most aging cells, particularly those involved in high lipid turnover (e.g., the adrenal medulla) or phagocytosis of other cell types (e g., the retinal pigment epithelium or RPE; macrophage). This term pertains if there is an increase in the extraneuronal accumulation of lipofuscin (also known as autofluorescent lipoprotein) more than expected for the age of the patient. Evidence: IEA. (OMIM:204500)
- Increased neuronal autofluorescent lipopigment (HP:0002074): Lipofuscin, a generic term applied to autofluorescent lipopigment, is a mixture of protein and lipid that accumulates in most aging cells, particularly those involved in high lipid turnover (e.g., the adrenal medulla) or phagocytosis of other cell types (e g., the retinal pigment epithelium or RPE; macrophage). This term pertains if there is an increase in the neuronal accumulation of lipofuscin (also known as autofluorescent lipoprotein) more than expected for the age of the patient. Evidence: IEA. (OMIM:204500)
- 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: IEA. (OMIM:204500)
- Progressive visual loss (HP:0000529): A reduction of previously attained ability to see. Evidence: IEA. (OMIM:204500)
- 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: IEA. (OMIM:204500)
- Retinal degeneration (HP:0000546): A nonspecific term denoting progressive loss of the retinal pigment epithelium (RPE) and/or neurosensory retinal cells. Evidence: IEA. (OMIM:204500)
- Myoclonus (HP:0001336): Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements. Evidence: IEA. (OMIM:204500)
- Curvilinear intracellular accumulation of autofluorescent lipopigment storage material (HP:0003205): An intracellular accumulation of autofluorescent lipopigment storage material in a curved pattern. Evidence: IEA. (OMIM:204500)
These phenotypes are associated with the disease neuronal ceroid lipofuscinosis 2 (OMIM:204500).