- Visual loss (HP:0000572): Loss of visual acuity (implying that vision was better at a certain time point in life). Otherwise the term reduced visual acuity should be used (or a subclass of that). Evidence: TAS. Frequency: Occasional (HP:0040283). (OMIM:300653)
- Juvenile onset (HP:0003621): Onset of signs or symptoms of disease between the age of 5 and 15 years. Evidence: PCS. Frequency: 1/1. (PMID:1547346)
- 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:300653)
- Rhabdomyolysis (HP:0003201): Breakdown of muscle fibers that leads to the release of muscle fiber contents (myoglobin) into the bloodstream. Evidence: IEA. (OMIM:300653)
- 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:300653)
- Myopathy (HP:0003198): A disorder of muscle unrelated to impairment of innervation or neuromuscular junction. Evidence: TAS. (OMIM:300653)
- Migraine (HP:0002076): Migraine is a chronic neurological disorder characterized by episodic attacks of headache and associated symptoms. Evidence: IEA. (OMIM:300653)
- Renal insufficiency (HP:0000083): A reduction in the level of performance of the kidneys in areas of function comprising the concentration of urine, removal of wastes, the maintenance of electrolyte balance, homeostasis of blood pressure, and calcium metabolism. Evidence: TAS. Frequency: Occasional (HP:0040283). (OMIM:300653)
- 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: 0/1. (PMID:1547346)
- 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:300653)
- Erythroid hyperplasia (HP:0012132): Increased count of erythroid precursor cells, that is, erythroid lineage cells in the bone marrow. Evidence: PCS. Frequency: 1/1. (PMID:1547346)
- X-linked recessive inheritance (HP:0001419): 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: PCS. (PMID:6933565)
- Hemolytic anemia (HP:0001878): A type of anemia caused by premature destruction of red blood cells (hemolysis). Evidence: PCS. Frequency: 1/1. (PMID:1547346)
- Emotional lability (HP:0000712): Unstable emotional experiences and frequent mood changes; emotions that are easily aroused, intense, and/or disproportionate to events and circumstances. Evidence: IEA. (OMIM:300653)
- Reticulocytosis (HP:0001923): An elevation in the number of reticulocytes (immature erythrocytes) in the peripheral blood circulation. Evidence: IEA. (OMIM:300653)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: PCS. Frequency: 1/1. (PMID:1547346)
- Exercise-induced myoglobinuria (HP:0008305): Presence of myoglobin in the urine following exercise. Evidence: TAS. (OMIM:300653)
- Retinal dystrophy (HP:0000556): Retinal dystrophy is an abnormality of the retina associated with a hereditary process. Retinal dystrophies are defined by their predominantly monogenic inheritance and they are frequently associated with loss or dysfunction of photoreceptor cells as a primary or secondary event. Evidence: IEA. Frequency: Occasional (HP:0040283). (OMIM:300653)
- Intellectual disability (HP:0001249): The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence. Evidence: PCS. Frequency: 1/2. (PMID:16567715;PMID:1547346)
- Exercise-induced muscle cramps (HP:0003710): Sudden and involuntary contractions of one or more muscles brought on by physical exertion. Evidence: PCS. Frequency: 1/1. (PMID:16567715)
- Exercise intolerance (HP:0003546): A functional motor deficit where individuals whose responses to the challenges of exercise fail to achieve levels considered normal for their age and gender. Evidence: IEA. (OMIM:300653)
These phenotypes are associated with the disease glycogen storage disease due to phosphoglycerate kinase 1 deficiency (OMIM:300653).