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.

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

A state of disinterestedness, listlessness, and indifference, resulting in difficulty performing simple tasks or concentrating.

Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles.

Functional neurological abnormalities related to dysfunction of the pyramidal tract.

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

An increase in size of the ventricular system of the brain.

Partial or complete wasting (loss) of brain tissue that was once present.

Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk.

Impairment of gas exchange within the lungs secondary to a disease process, neoplasm, or trauma, possibly resulting in hypoxia, hypercarbia, or both, but not requiring intubation or mechanical ventilation. Patients are normally managed with pharmaceutical therapy, supplemental oxygen, or both.

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

Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.

Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy.