An increased concentration of lactic acid in the urine.

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

Abnormally increased size of the liver.

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

An inadequate sucking reflex, resulting in the difficult of newborns to be breast-fed.

A form of hepatic steatosis characterized by the presence of large, lipid-laden vesicles in the affected hepatocytes.

A form of hepatic steatosis characterized by the presence of small, lipid-laden vesicles in the affected hepatocytes.

A condition in which the stomach contents leak backwards from the stomach into the esophagus through the lower esophageal sphincter.

The Premie-Neuro and the Dubowitz Neurological Examination score head lag in the same manner. Scoring for both is as follows

Increased concentration of lactate in the cerebrospinal fluid.

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.

Difficulty to maintain correct position of the head while standing or sitting. Infant head lag is observed when the head seems to flop around or lags posteriorly behind the trunk. Several articles have maintained that head lag should be absent by age 3 to 4 months.

An abnormally high degree of muscle fiber size variation. This phenotypic feature can be observed upon muscle biopsy.

Muscular hypotonia (abnormally low muscle tone) manifesting in the neonatal period.

Stridor is a high pitched sound resulting from turbulent air flow in the upper airway.

Respiratory distress is objectively observable as the physical or emotional consequences from the experience of dyspnea. The physical presentation of respiratory distress is generally referred to as labored breathing, while the sensation of respiratory distress is called shortness of breath or dyspnea.

An abnormal buildup of lactic acid in the body, leading to acidification of the blood and other bodily fluids.

Presence of elevated levels of ketone bodies in the body.

The concentration of aspartate aminotransferase (AST) in the blood circulation is above the upper limit of normal.

An abnormally high concentration in the circulation of alanine aminotransferase (ALT).

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.

Increased level of the enzyme gamma-glutamyltransferase (GGT). GGT is mainly present in kidney, liver, and pancreatic cells, but small amounts are present in other tissues.

The mitochondrial matrix refers to the substance occupying the space enclosed by the inner membrane of a mitochondrion, which contains enzymes, DNA, granules, and inclusions of protein crystals, glycogen, and lipid. Mitochondrial swelling refers to an increase in size of the mitochondrial matrix. This phenomenon is thought to be related to a permeabilized inner membrane that originates a large swelling in the mitochondrial matrix. Mitochondrial swelling may distend the outer membrane until it ruptures.