A functional motor deficit where individuals whose responses to the challenges of exercise fail to achieve levels considered normal for their age and gender.

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

Subnormal intellectual functioning which originates during the developmental period. Intellectual disability, previously referred to as mental retardation, has been defined as an IQ score below 70.

A type of anemia characterized by an abnormally low concentration of hemoglobin in the erythrocytes.

Sideroblastic anemia results from a defect in the incorporation of iron into the heme molecule. A sideroblast is an erythroblast that has stainable deposits of iron in cytoplasm (this can be demonstrated by Prussian blue staining).

Increased count of erythroid precursor cells, that is, erythroid lineage cells in the bone marrow.

A type of erythrocyte inclusion characterized by basophilic stippling of erythrocytes, that is, by numerous very small coarse or fine blue granules within the cytoplasm with the additional stipulation that the stippled particles are due to iron granules (demonstrable by the Prussian blue stain).

A kind of anemia in which the volume of the red blood cells is reduced.

Developmental hypoplasia of the mandible.

Generalized (unlocalized) atrophy affecting muscles of the limbs in both proximal and distal locations.

An abnormally reduced activity of the enzyme cytochrome C oxidase in muscle tissue.

Head circumference below 2 standard deviations below the mean for age and gender.

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

Increased concentration of ferritin in the blood circulation.

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).

Height of the palate more than 2 SD above the mean (objective) or palatal height at the level of the first permanent molar more than twice the height of the teeth (subjective).

Abnormally pale skin.

Double rows of eyelashes.

Passing the age when puberty normally occurs with no physical or hormonal signs of the onset of puberty.