An increased concentration of dicarboxylic acid in the urine.

Hypertrophic cardiomyopathy (HCM) is defined by the presence of increased ventricular wall thickness or mass in the absence of loading conditions (hypertension, valve disease) sufficient to cause the observed abnormality.

The presence of an abnormality of cardiac function that is responsible for the failure of the heart to pump blood at a rate that is commensurate with the needs of the tissues or a state in which abnormally elevated filling pressures are required for the heart to do so. Heart failure is frequently related to a defect in myocardial contraction.

A large reduction in the fraction of blood pumped from the left ventricle with each cardiac cycle. The normal range in adults is at over 50 percent, and a severe reduction is defined as less than 30 percent.

Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm.

Hard, pebble-like deposits that form within the gallbladder.

Forceful ejection of the contents of the stomach through the mouth by means of a series of involuntary spasmic contractions.

Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it.

Abnormal accumulation of fluid in the brain.

Apathy is a quantitative reduction of interest, motivation and the initiation and persistence of goal-directed behavior, where often the accompanying emotions, thoughts, and social interactions are also diminished. The individual is typically non-reactive to provocations, positive or negative, and appears to not care. Distinguished from lethargy which involves lack of physical or mental energy.

Migraine is a chronic neurological disorder characterized by episodic attacks of headache and associated symptoms.

A loss of myelin from nerve fibers in the central nervous system.

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.

Attention-deficit/hyperactivity disorder (ADHD) is a behavioral disorder that typically begins in childhood and is characterized by a short attention span (inattention), an inability to be calm and stay still (hyperactivity), and poor impulse control (impulsivity). Some people with ADHD have problems with only inattention or with hyperactivity and impulsivity, but most have problems related to all three features.\n\nIn people with ADHD, the characteristic behaviors are frequent and severe enough to interfere with the activities of daily living such as school, work, and relationships with others. Because of an inability to stay focused on tasks, people with inattention may be easily distracted, forgetful, avoid tasks that require sustained attention, have difficulty organizing tasks, or frequently lose items.\n\nHyperactivity is usually shown by frequent movement. Individuals with this feature often fidget or tap their foot when seated, leave their seat when it is inappropriate to do so (such as in the classroom), or talk a lot and interrupt others.\n\nImpulsivity can result in hasty actions without thought for the consequences. Individuals with poor impulse control may have difficulty waiting for their turn, deferring to others, or considering their actions before acting.\n\nIn most affected individuals, ADHD continues throughout life, but in about one-third of individuals, signs and symptoms of ADHD go away by adulthood.\n\nMore than two-thirds of all individuals with ADHD have additional conditions, including insomnia, mood or anxiety disorders, learning disorders, or substance use disorders. Affected individuals may also have autism spectrum disorder, which is characterized by impaired communication and social interaction, or Tourette syndrome, which is a disorder characterized by repetitive and involuntary movements or noises called tics.

Loss of developmental skills, as manifested by loss of developmental milestones.

A deviation from normal signal on magnetic resonance imaging (MRI) of the basal ganglia.

An increase in the level of lactate in the brain identified by magnetic resonance spectroscopy (MRS).

Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.

Lack of breathing with no movement of the respiratory muscles and no exchange of air in the lungs. This term refers to a disposition to have recurrent episodes of apnea rather than to a single event.

An increased concentration of alanine in the blood.

Low blood glucose is accompanied by elevated levels of ketone bodies in the body.

Abnormally increased level of blood lactate (2-hydroxypropanoic acid). Lactate is produced from pyruvate by lactate dehydrogenase during normal metabolism. The terms lactate and lactic acid are often used interchangeably but lactate (the component measured in blood) is strictly a weak base whereas lactic acid is the corresponding acid. Lactic acidosis is often used clinically to describe elevated lactate but should be reserved for cases where there is a corresponding acidosis (pH below 7.35).

A nonspecific term denoting degeneration of the retinal pigment epithelium and/or retinal photoreceptor cells.

A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.

A reduction in the activity of the mitochondrial respiratory chain complex I, which is part of the electron transport chain in mitochondria.

A reduction in the activity of the mitochondrial respiratory chain complex IV, which is part of the electron transport chain in mitochondria.