Category: H

Harlequin fetus (HF) is a rare disorder of keratinization, the process by which skin tissue forms and eventually sloughs off the body. It most likely represents several genetic mutations that have common clinical findings.  

Hypoplastic left heart syndrome (HLHS) describes a group of complex congenital heart defects that occur in newborns. HLHS is characterized by the underdevelopment of the left atrium and ventricle of the heart. Additionally, the valve that connects these two chambers (the mitral orifice) and the aortic valve are narrowed or closed. The defects on the…

Hypochondroplasia is a rare, hereditary type of short- limbed dwarfism. Originally described in 1913, this disorder has many similarities to achondroplasia, with which it is, and has been, often confused. Physical findings in hypochondroplasia include short stature, mildly shortened extremities, malformed vertebrae of the lower spine, and nearly normal appearance of the face and head.…

Hypertonia is increased tension of the muscles that can make movement difficult. It can also be defined as resistance to passive movement that is not velocity dependent. Hypertonia usually occurs in definite patterns of flexion or extension. Difficulties are most predominant in the flexor patterns for the upper extremities and in the extensor patterns of…

Hyperlexia is defined as the ability of an individual to recognize words at a level superior to that predicted by their age and measured intellectual ability, which is significantly better than their reading comprehension. The prevalence of hyperlexia is unknown, but as with most developmental disorders, it occurs three to four times as often in…

Hydrolethalus syndrome is a recessively inherited lethal malformation syndrome involving the central nervous system. Prenatal diagnosis is most common, and the fetuses commonly present with hydrocephaly (with significant functional deficits), micrognathia (underdevelopment of the jaw), polydactyly (more than the normal number of fingers and toes), and a key-shaped defect of the occipital bone.  

Hutchinson-Gilford progeria syndrome is a very rare progressive disorder characterized by an appearance of accelerated aging in children (National Organization for Rare Disorders [NORD], 2000). Progeria is a Greek term meaning “prematurely old.” The classic type is Hutchinson- Gilford progeria syndrome, first described in England in 1886 by Jonathan Hutchinson and again in 1886 and…

Hunter syndrome (mucopolysacchridosis II, or MPS II), a progressive disorder arising from a deficiency in the enzyme iduronate sulfatase, is a sex-linked inborn error of metabolism (IEM) affecting only males. The enzyme’s absence or deficiency prevents complete breakdown of the mucopolysacchrides heparen sulphate and dermatan sulfate, which then accumulate in bodily cells. One of a…

Holt-Oram syndrome, also known as heart-hand syndrome or cardiac-limb syndrome, refers to a rare genetic condition involving abnormalities of the heart and upper limbs. Those affected have malformations or abnormalities of the bones in the thumbs, wrists, and arms, but lower extremities are not affected. Bones may be missing, extra, underdeveloped, or malformed. There may…