Glossary of Key Terms for Teratology Maria dos Anjos Pires and Ana M. Calado Introduction Teratology (from the Greek, teratos, monster) is the science that studies birth defects, congenital malformations, or developmental disorders and is a complex science to understand. The effort to make it more accessible comprises the construction of a glossary with the most routine used terms, making them more comprehen- sive and accessible. The purpose of this glossary is to make this subject more understandable for all those who want or need to learn this subject. Glossary Abiotrophy A group of diseases that are characterized by the premature spontaneous neuron degeneration, and also storage neuron diseases that affected them diffusely. It is limited to a metabolic development and intrinsic error to the neuron that limits its viability and is identified in the inborn. Acardia Absence of the heart. Severe congenital defect conjoint with other anom- alies present in one element of a pair of twin. Achondroplasia Anomaly subsequent to a defect of bone grown resulting in an insuffi- cient growth (dwarfism), associated with other skeletal abnormalities (macrocephaly, kyphosis, short limbs). Acromegaly Disproportional enlargement of the face, hands, and feet. Luís Félix (ed.), Teratogenicity Testing: Methods and Protocols, Methods in Molecular Biology, vol. 1797, https://doi.org/10.1007/978-1-4939-7883-0, © Springer Science+Business Media, LLC, part of Springer Nature 2018 595 596 Maria dos Anjos Pires and Ana M. Calado Agenesis or aplasia Complete absence of an organ due to nonappearance of its primor- dium in the embryo (examples: anencephaly, cyclopia, amelia, renal agenesis). This is lethal when the affected organ is unique and essential (example: microcephaly) or both bilateral organs (as kidney and lung). Albinism Globally reducing or absence of pigmentation in eye, hair, or skin, related to congenital defects of tyrosinase, a copper-­contained enzyme involved in the melanin synthesis. Amelia Refers to the absence of one or more limbs. It is a sporadic anomaly. It can present as an isolated defect or with associated malformations, par- ticularly abdominal wall and renal anomaly. Amniotic band sequence (ABS) Is a group of structural abnormalities that involve mostly the limbs, but may also affect the craniofacial region and trunk. ABS is perhaps the most common example of intrauterine disruption. The specific malfor- mations caused depend upon the time of the disruption. The typical appearance consists of amputations and malformations caused by the encircling constrictions of the limbs or other body structures, but the clinical spectrum is highly variable. Amyoplasia Generalized lack of muscle growth and development, which has, as a consequence, arthrogryposis, a contracture and deformity of the most joints. Anencephaly Is a lethal anomaly with the absence of brain formation or its degeneration as a consequence of cranioschisis (absence of cranial vault formation). Aniridia Absence of the iris. The eye could be complete only without the iris. Ankyloglossia Extension of the tong frenulum to the tip of the tongue, instead it may only be in the base of the tongue where they anchor to the mouth floor. Anophtalmia Absence of the eye. Most times, this is accompanied by severe cranial abnormalities. Anotia Complete absence of external structure of the ear. Aphakia Congenital anomaly with the absence of the eye lens. Aplasia Developmental disturbance in which only a tissue or organ rudiments occur. In some cases, there is no formation of an organ. Development has begun, but this was interrupted early. The organ is composed only by rudiment. Arnold-Chiari malformation Herniation of part of the cerebellum into the foramen magnum obstruct- ing the flow of the cerebrospinal fluid. Glossary of Key Terms for Teratology 597 Arthrogryposis Congenital joint contractures, involving more than one joint, inducing abnormal position of the limbs. This anomaly could be related by amyoplasia. Association Non-random association of two or more anomalies, which are not pathogenically related, and occur together more frequently than expected. Most associations are classified as “Polytopic Field Defects.” As examples, the VATER or VACTERL association includes Vertebral anomalies, Anal atresia, Cardiac defects, TE fistula (tracheoesophageal fistula),R enal defects, and Limb defects. As the anomalies in these asso- ciations tend to occur together more frequently, the finding of one of these should prompt the clinician to look for related ones. Atresia A condition in which an orifice, lumen, or passage of the body has incom- plete formation, resulting in an abnormality of this aperture, that will be closed or absent. This situation only occurs in tubular organs (examples: Sylvius aqueduct, biliary atresia; oesophageal atresia, anal atresia). Atrichia Congenital absence of hair. This malformation could be associated with other ectodermal anomalies such as teeth and nails anomalies. Atrophy Decrease in size of a normally developed tissue or organ, derived from a decrease in cell size and/or cell number. This process could be physiologic (during the normal embryonic development some structures need to atrophy, as the thyroglossal duct), or pathologic (e.g., after an immobiliz- ing as a consequence of a fracture, the muscle atrophies). In general, this anomaly is associated with apoptosis and autophagy, usually related to a decrease in the number of cytoplasmic organelles, and consequently a reduction in cellular volume and function. Brachycephaly Is a cephalic disorder. The skull has a distinct shape and shorter than characteristic for its species (as in some dog and cat breeds). In man, it is the result of premature closure (craniosynostosis) of the coronal suture resulting in short skull. Brachydactyly The digits are shortened, when compared to the size of other long bones. This anomaly could be associated with other anomalies (as dysmelia) or as part of congenital syndromes. Cachexia Poor body condition related to low weight as a consequence of diverse anomalies (as cardiac congenital anomalies). Cephalopagus The same as janiceps, these joint twins are fused ventrally from the top of the head down including the umbilicus. They share the head, neck, thorax, abdomen. The lowered abdomen, genitalia, vertebral column, and limbs are individualized. The head has a deformed face, in general in opposite sites. 598 Maria dos Anjos Pires and Ana M. Calado Cheiloschisis Congenital cleft in the middle upper lip. Choristia Presence of normal tissue in an unusual place (heterotopia), due to a local congenital error of development. Examples: pancreatic tissue in the gastric walls, adrenal cortex in the kidneys, lungs in the ovary, and endo- metrium in the ovary. Cleft Openings resulting from non-fusion of embryonic structures, by delay or stopped in the embryonic development at the stage corresponding to the formation of the structure. This results in an inadequate aper- ture of the structure or organ (ex. cleft palate). Coloboma Cleft in eye structures. It could be only in the iris (coloboma iris) or be extended to the retina, choroid, ciliary, and optical nerve. This malfor- mation is the result of the closing miscarriage of choroid fissure during the fetal development. Conjoined twin Congenital defects of the twins that are fused by a part of its bodies (head, thorax, abdomen, column, hip, etc.) with different organs fusion and dependency. Some of these situations are severe, implying the death of the twins. The denomination depends on the part that is fused and the extension of its union. Craniopagus Conjoined twins fused by any portion of cranial vault, but never involv- ing neither the foramen magnum nor the basis of the skull, the face nor the vertebrae. Craniopagus Conjoined twins fused by the cranium (united skulls). In this case the twins could be fused by any part of the skull except the foramen mag- num or face. The rest of the body is divided. Cranioschisis Failure in the formation of the cranial vault. The encephalic tissue is exposed to the amniotic fluid, resulting in degeneration and loss of this (anencephaly). Craniosysnostosis Premature closure of one or more sutures of the cranium, resulting in an abnormal shape of the skull. Criptorchidia Failure of total or partial (cryptorchidism) fall of the testicles to the scrotum through the inguinal canal (ring). The abnormal position of these organs can be inside the abdomen or in the abdominal wall. Cyclopia Severe congenital disorder with the existence of only one eye in the face, with a non-functional nose (most of times as a trumpet). This anomaly is related to other malformations as encephalon disorders. This malfor- mation is mostly incompatible with the new-born survival. Glossary of Key Terms for Teratology 599 Deformation Are abnormal form, shape, or position of a part of the body due to mechanical forces. Extrinsic forces include multiple gestations, intra- uterine mechanical forces that modify a normally formed structure. Intrauterine forces, such as decreased amniotic fluid, uterine tumors, and uterine malformations, can lead to fetal compression. Intrinsic forces include torticollis, arthrogryposis, neuromuscular abnormalities, amyoplasia, or skeletal anomalies. These anomalies have a good prog- nosis and are typically easy to treat with physical therapy or external fixation devices. Developmental field defect One or more developmental defects interrelated in an organ or region (e.g., “Monotopic Field