Hypoplasia is the medical-histological term that describes an incomplete development of a tissue or organ, resulting from an insufficient or inferior number of cells.

Enamel hypoplasia

Hypoplasia is similar to aplasia, but is less severe. Thus, a hypoplastic organ is more developed than an aplasic organ.

Among the organs and tissues that can be subject to hypoplasia, we note: the testicles, the optic nerve, the ovaries, the heart, the enamel of the teeth, the thymus, the uterus, the corpus callosum, the cerebellum, the thumb, the pectoral muscles and the breasts.

Definition of hypoplasia

Hypoplasia is the term that, in the medical-histological context, indicates the underdevelopment or incomplete development of a tissue or organ, due to an insufficient or inferior number of cells.


In medicine and histology, aplasia is the failure to develop an organ or tissue; "failed development" means "development not completed".

Hypoplasia is similar to aplasia, but is less severe. This means that an organ or tissue affected by hypoplasia is more developed than an organ or tissue affected by aplasia.


The word "hypoplasia" derives from the union of two terms of Greek origin, which are "ipo" (ὑπo) and "plasis" (πλάσις). The term "hypo" means "below" or "inferior", while the term "plasis" means "formation". Thus, the meaning of hypoplasia is "under-formation".


There are various types of hypoplasia . Among the most well-known types of hypoplasia, they certainly deserve a quote:

  • Testicular hypoplasia, in conditions such as male hypogonadism, Klinefelter syndrome, varicocele, orchitis, etc .;
  • Hypoplasia of the optic nerve;
  • Enamel hypoplasia, also called Turner's tooth ;
  • The two cardiac hypoplasias, known as hypoplastic left heart syndrome and hypoplastic right heart syndrome ;
  • Thymus hypoplasia, in DiGeorge syndrome ;
  • Uterine hypoplasia;
  • Hypoplasia of the corpus callosum;
  • The hypoplasia of the depressor muscle of the corner of the mouth. To learn more about the depressor muscle of the corner of the mouth, readers can consult the article here;
  • Monolateral hypoplasia of pectoral muscles in a condition known as Poland syndrome ;
  • Ovarian hypoplasia, also known as ovarian hypoplasia;
  • Nail hypoplasia, in conditions such as Turner syndrome ;
  • Mammary hypoplasia, also known as breast hypoplasia;
  • Cerebellar hypoplasia, ie the hypoplasia of the cerebellum;
  • Thumb hypoplasia, also called congenital thumb hypoplasia ;
  • Mandibular hypoplasia, in Goldenhar syndrome ;
  • Lung hypoplasia, ie the hypoplasia of the lungs.

The article briefly describes the causes and consequences of some of the aforementioned types of hypoplasia.


Also known as hypotrophy of the testicles or simply small testicles, testicular hypoplasia is potentially responsible for: reduced spermatogenesis, with consequent decrease in fertility, and decrease in the production of steroid hormones, with consequent failure or incomplete development of secondary sexual characteristics (eg : pubic hair, beard etc.).


The optic nerve is a collection of nerve fibers, having the important task of transmitting the visual signals from the organs of sight - namely the eyes - to the brain, for the processing of sight .

Identified with the Roman number 2 (II), the optic nerve represents one of the twelve pairs of cranial nerves .

In general, people with optic nerve hypoplasia complain of more or less marked visual difficulties affecting one or both eyes, mono- or bilateral nystagmus and a degree of strabismus .

In some circumstances, the hypoplasia of the optic nerve is associated with some particular malformations of the central nervous system, from which the presence of epileptic seizures and developmental delay may depend.


Enamel hypoplasia is an anomaly of the teeth, in the presence of which the dental enamel, although having normal hardness, is extremely thin, scarce in quantity and, at times, covered with holes, which expose the dentin .

At the base of the enamel hypoplasia, there is a wrong process of formation of the so-called enamel matrix (or enamel matrix).

The causes of enamel hypoplasia include nutritional deficiency, celiac disease, congenital syphilis, hypocalcemia, premature birth, deciduous dentition trauma and fluorosis.


The heart of the human being is ideally divided into two halves: a right half and a left half.

Composed of a right atrium and a right ventricle, the right half of the heart has the task of sending oxygen-poor blood to the lungs, coming from the organs and tissues of the body.

Consisting of the left atrium and the left ventricle, on the other hand, the left half of the heart has the task of pumping oxygenated blood back from the lungs to the organs and tissues of the body.

Hypoplastic left heart syndrome is a rare congenital cardiac malformation characterized by an underdevelopment of the left half of the heart (and its valves).

Its presence involves different blood circulation difficulties, both as regards the passage of blood from the left atrium to the left ventricle and as regards the passage from the left ventricle to the aorta.

The symptomatic picture of hypoplastic left heart syndrome can be seen from birth and usually consists of: cyanosis, breathing difficulties, cold hands and feet, drowsiness and shock.


Hypoplastic right heart syndrome is another rare congenital cardiac malformation, characterized by incomplete development of the right atrium and right ventricle (and their valves).

Its presence causes a reduced blood supply to the lungs, with consequent poor blood oxygenation. Because of poor blood oxygenation, the patient manifests cyanosis in various parts of the body, including: skin, lips and the ends of the fingers.


Uterine hypoplasia is a congenital malformation that involves the presence of a small uterus.

Part of the so-called Müllerian duct anomalies (such as uterine agenesis or Müllerian agenesis), uterine hypoplasia is responsible for: primary amenorrhea, poor vaginal opening and infertility.


Cerebellar hypoplasia represents a heterogeneous group of cerebellar malformations, all of which involve a very similar symptomatological picture, including: early onset non-progressive ataxia, hypotonia and motor learning deficits.

Possible causes of cerebellar hypoplasia include: hereditary factors, severe metabolic abnormalities, viral agents and / or toxic agents.


Congenital hypoplasia of the thumb is an anomaly present from birth, which is characterized by an underdevelopment more or less evident in the thumb of one or both hands.

Typical sign of conditions such as Holt-Oram syndrome, VATER syndrome, TAR syndrome and Fanconi anemia, thumb hypoplasia affects one subject every 100, 000 newborns.