- Bilateral tonic-clonic seizure (HP:0002069): A bilateral tonic-clonic seizure is a seizure defined by a tonic (bilateral increased tone, lasting seconds to minutes) and then a clonic (bilateral sustained rhythmic jerking) phase. Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Hypertonia (HP:0001276): A condition in which there is increased muscle tone so that arms or legs, for example, are stiff and difficult to move. Evidence: IEA. (OMIM:272300)
- Floppy infant (HP:0008947): Floppiness/hypotonia is defined as reduced resistance to passive movement of joints. Physical examination of floppy/hypotonic infants shows head lag, lack of shoulder and elbow muscle contraction on traction response, inability to tighten the shoulder girdle muscles (or slipping through) when held under the axillae, scarf sign (when the arm is pulled to the opposite side, the arm wraps around the neck with the elbow crossing midline), hyperdorsiflexion of the feet, easy apposition of the thumb against the forearm, feet touching the cheek with ease and without discomfort, frog leg position, and inverted U sign on ventral suspension (head, arms, and legs hanging down without elbow or knee flexion and the trunk rounded in a dome shape). Evidence: TAS. (OMIM:272300)
- Narrow forehead (HP:0000341): Width of the forehead or distance between the frontotemporales is more than two standard deviations below the mean (objective); or apparently narrow intertemporal region (subjective). Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Hemiplegia (HP:0002301): Paralysis (complete loss of muscle function) in the arm, leg, and in some cases the face on one side of the body. Evidence: IEA. (OMIM:272300)
- Elevated circulating creatine kinase activity (HP:0003236): The activity of creatine kinase in the blood circulation is above the upper limit of normal. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Delayed eruption of teeth (HP:0000684): Delayed tooth eruption, which can be defined as tooth eruption more than 2 SD beyond the mean eruption age. Evidence: TAS. (OMIM:272300)
- 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:272300)
- Generalized hypotonia (HP:0001290): Generalized muscular hypotonia (abnormally low muscle tone). Evidence: TAS. (OMIM:272300)
- Multifocal epileptiform discharges (HP:0010841): An abnormality in cerebral electrical activity recorded along the scalp by electroencephalography (EEG) and being identified at multiple locations (foci). Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Severe intellectual disability (HP:0010864): Severe intellectual disability (ID) is defined as a type of ID characterized by severely sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 20-34. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Cerebral visual impairment (HP:0100704): A form of loss of vision caused by damage to the visual cortex rather than a defect in the eye. Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Agitation (HP:0000713): A state of excessive motor activity that is associated with mental distress or a feeling of substantial unease or inner tension. Distinguished from restlessness by the increased level of emotional distress and negative intensity of the experience. Agitation has a significant level of physical activity that is typically threatening to the self or others. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Death in infancy (HP:0001522): Death within the first 24 months of life. Evidence: TAS. (OMIM:272300)
- Generalized dystonia (HP:0007325): A type of dystonia that affects all or most of the body. Evidence: IEA. (OMIM:272300)
- Metabolic acidosis (HP:0001942): Metabolic acidosis (MA) is characterized by a fall in blood pH due to a reduction of serum bicarbonate concentration. This can occur as a result of either the accumulation of acids (high anion gap MA) or the loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic MA). By definition, MA is not due to a respirary cause. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 2/2. (PMID:15952210;PMID:31127934)
- Axial hypotonia (HP:0008936): Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk. Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Fine hair (HP:0002213): Hair that is fine or thin to the touch. Evidence: IEA. (OMIM:272300)
- Sulfite oxidase deficiency (HP:0003643): Abnormally reduced sulfite oxidase level. Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: PCS. Frequency: 2/2. (PMID:15952210;PMID:31127934)
- Cerebral atrophy (HP:0002059): Atrophy (wasting, decrease in size of cells or tissue) affecting the cerebrum. Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Absent speech (HP:0001344): Complete lack of development of speech and language abilities. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Choreoathetosis (HP:0001266): Involuntary movements characterized by both athetosis (inability to sustain muscles in a fixed position) and chorea (widespread jerky arrhythmic movements). Evidence: IEA. (OMIM:272300)
- Cerebellar hypoplasia (HP:0001321): Cerebellar hypoplasia is a descriptive term implying a cerebellum with a reduced volume, but a normal shape and is stable over time. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Deeply set eye (HP:0000490): An eye that is more deeply recessed into the plane of the face than is typical. Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Episodic vomiting (HP:0002572): Paroxysmal, recurrent episodes of vomiting. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Global developmental delay (HP:0001263): A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age. Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Increased urinary sulfite level (HP:0011942): The concentration of SO3(2-), i.e., sulfite, in the urine, normalized for urine concentration, is above the upper limit of normal. Evidence: TAS. (OMIM:272300)
- Ectopia lentis (HP:0001083): Dislocation or malposition of the crystalline lens of the eye. A partial displacement (or dislocation) of the lens is described as a subluxation of the lens, while a complete displacement is termed luxation of the lens. A complete displacement occurs if the lens is completely outside the patellar fossa of the lens, either in the anterior chamber, in the vitreous, or directly on the retina. If the lens is partially displaced but still contained within the lens space, then it is termed subluxation. Evidence: IEA. (OMIM:272300)
- Dyskinesia (HP:0100660): A movement disorder which consists of effects including diminished voluntary movements and the presence of involuntary movements. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Sulfocysteinuria (HP:0032350): A increased concentration of sulfocysteine in the urine. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- Hyperintensity of cerebral white matter on MRI (HP:0030890): A brighter than expected signal on magnetic resonance imaging emanating from the cerebral white matter. Evidence: PCS. Frequency: 1/1. (PMID:31127934)
- 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:15952210)
- Eczematoid dermatitis (HP:0000964): Eczema is a form of dermatitis that is characterized by scaly, pruritic, erythematous lesions located on flexural surfaces. Evidence: IEA. (OMIM:272300)
- Macrotia (HP:0000400): Median longitudinal ear length greater than two standard deviations above the mean and median ear width greater than two standard deviations above the mean (objective); or, apparent increase in length and width of the pinna (subjective). Evidence: PCS. Frequency: 1/1. (PMID:15952210)
- Decreased urinary sulfate (HP:0003359): Decreased concentration of sulfate in the urine. Evidence: TAS. (OMIM:272300)
These phenotypes are associated with the disease isolated sulfite oxidase deficiency (OMIM:272300).