Keywords: Chapter 6, Developmental & Genetic Disorders
Achondroplastic dwarfism/achondroplasia
An autosomal dominant, hereditary disturbance of epiphyseal chrondroblastic development that leads to inadequate enchondral bone formation.
Agenesis
Complete absence of an organ primordium.
Albinism
A heterogeneous group of at least 10 inherited disorders of pigmentation characterized by absent or reduced biosynthesis of melanin.
Alcaptonuria
A rare autosomal recessive disease characterized by excretion of homogentisic acid in the urine, generalized pigmentation, and arthritis. Due to deficiency in hepatic and renal homogentisic acid oxidase.
Amniocentesis
Surgical transabdominal perforation of the uterus with a needle, to obtain amniotic fluid.
References: - MMWR 44 (RR-9), 1995. Chorionic villus sampling and amniocentesis. Recommendations for prenatal counseling.
Anencephaly
The congenital absence of the cranial vault, with cerebral hemispheres completely missing or reduced to small masses attached to the base of the skull.
Angelman syndrome
Synonomous with the "happy puppet" syndrome. May have microdeletion of 15q11-12. Deletion is maternal in Angelman syndrome and paternal in Prader-Willi syndrome. These children have severe mental retardation, seizures, no speech, paroxysms of laughter, microcephaly, prognathism, and ocular abnormalities. Important as an example the effects of genomic imprinting
Aplasia
Absence of an organ coupled with persistence of the organ anlage (primordium) or a rudiment that never develops completely.
Atresia
Defects caused by the incomplete formation of a lumen.
Autosomal dominant disorder
Single gene abnormalities that are expressed in heterozygotes.
Autosomal recessive disorder
These disorders are only associated with clinical symptoms when both alleles at a given locus on homologous chromosomes are defective.
Cephal-hematoma
A subperiosteal hemorrhage confined to a single cranial bone which becomes apparent within the first few hours after birth.
Cleft lip/palate
An example of multifactorial inheritance, it is caused by hereditary or environmental disturbance in gene expression in the genes involved in fusion of the frontal prominence with the maxillary process to form the upper lip. It may or may not include cleft palate.
Cystic fibrosis
An autosomal recessive disorder affecting children that is characterized by (1) chronic pulmonary disease; (2) deficient exocrine pancreatic function; and (3) other complications of inspissated mucus in a number of organs, including the small intestine, liver and reproductive tract.
Duchenne muscular dystrophy
The most common variant of a number of devastating wasting muscle diseases, most of which are X-linked.
Dysplasia
Abnormal organization of cells into tissues, a situation that results in abnormal histogenesis histogenesis.
Dysraphic anomalies
Defects caused by failure of apposed structures to fuse.
Dystopia
Retention of an organ at a site where it is located during development.
Ectopia
An anomaly in which an organ is outside its normal anatomic site.
Ehlers-Danlos syndromes
A group of rare, autosomal dominant inherited disorders of connective tissue that are characterized by remarkable hyperelasticity and fragility of the skin, joint hypermobility, and often a bleeding diathesis.
Erythroblastosis fetalis
A hemolytic disease of the fetus or newborn caused by the transplacental passage of maternal antibodies against fetal erythrocytes.
Familial hypercholesterolemia
A common autosomal dominant disorder characterized by striking acceleration of atherosclerosis and its complications.
Fetal alcohol syndrome
The syndrome is a complex of abnormalities induced by the maternal consumption of alcoholic beverages that includes: 1) growth retardation; 2) dysfunction of the central nervous system; and 3) characteristic facial dysmorphology.
References:- MMWR 44, April 1995. Fetal alcohol syndrome update.
Fragile X
Associated with the expansion of a trinucleotide repeat on the X chromosome and is the most common form of inherited mental retardation.
Gaucher disease
A lysosomal storage disease caused by a deficiency in glucocerebrosidase, characterized by accumulation of glucosylceramide, primarily in the lysosomes of macrophage.
Genomic imprinting
The differential expression of genetic material, at either a chromosomal or allelic level, depending on whether the genetic material has been inherited from the male or the female parent.
Glycogenoses
A group of at least 10 distinct autosomal recessive disorders characterized by accumulation of glycogen, principally in the liver, skeletal muscle, and heart. Each type of glycogenosis reflects a deficiency of one of the specific enzymes involved in metabolism of glycogen.
Hemophilia
Hemophilia A is an X-linked recessive disorder of blood clotting that results in spontaneous bleeding, particularly in joints, muscles, and internal organs. Hemophilia A results from a mutated gene coding for factor VIII. Hemophilia B is caused by a defect in the gene coding for factor IX.
Hurler syndrome
The most severe clinical form of mucopolysaccharidosis.
Hydrops fetalis
The most serious form of erythroblastosis fetalis in liveborn infants. Characterized by severe edema, secondary to congestive heart failure caused by severe anemia.
Hypoplasia
Reduced size owing to the incomplete development of all or part of an organ.
Kernicterus
Also termed bilirubin encephalopathy, defined as a neurologic condition associated with severe jaundice and characterized by bile staining of the brain, particularly of the basal ganglia, pontine nuclei, and dentate nuclei in the cerebellum.
Klinefelter syndrome
Also called testicular dysgenesis, is the phenotype of the 47,XXY genotype and is characterized by male hypogonadism and infertility.
Lysosomal storage diseases
Autosomal recessive disorders characterized by the accumulation of unmetabolized normal substrates in the lysosomes, owing to deficiencies of specific acid hydrolases.
Marfan syndrome
An autosomal dominant, inherited disorder of connective tissue characterized by a variety of abnormalities in many organs, including the heart, aorta, skeleton, eyes, and skin.
Mitochondrial genes
DNA which is unique to the mitochondria, present in many copies per cell and maternally inherited.
Mucopolysaccharidoses
An assortment of lysosomal storage diseases characterized by accumulation of glycosaminoglycans (mucopolysaccharides) in many organs. All of these disorders are inherited as autosomal recessive traits, with the exception of hunter syndrome, which is x-linked recessive.
Myelomeningocele
A neural tube defect characterized by a hernial protrusion of the spinal cord and its meninges through a defect in the vertebral column.
Neonatal respiratory distress syndrome
A life-threatening disorder of the lungs principally associated with prematurity and the lack of surfactant.
Neurofibromatoses
Two distinct autosomal dominant disorders characterized by development of multiple neurofibromas, which are benign tumors of peripheral nerves of Schwann cell origin.
Niemann-Pick syndrome
A heterogenous group of disorders that are characterized by the lysosomal storage of sphingomyelin, cholesterol, and other glycolipids in macrophages.
Osteogenesis imperfecta
Also called brittle bone disease, comprises a group of inherited disorders in which a generalized abnormality of connective tissue is expressed principally as fragility of bone. Most cases of oi are inherited in an autosomal dominant pattern.
Phenylketonuria
(PKU, hyperphenylalaninemia) is an autosomal recessive disorder caused by a deficiency of the hepatic enzyme phenylalanine hydroxylase and characterized by progressive mental deterioration in the first few years of life. The severe brain damage in PKU results from high levels of circulating phenylalanine.
Prader-Willi syndrome
Clinical features are hypotonia and difficulty with feeding at birth, hyperphagia and excessive obesity in childhood. Hypoplasia of the external genitalia in boys, small hands and feet, psychomotor retardation, and seizures. About two-thirds of patients with Prader-Willi syndrome a have a detectable deletion of 15q11-12. Important as an example of the effects of genomic imprinting.
Prematurity
Defined by the World Health Organization as a newborn with a gestational age of less than 37 weeks from first day of the last menstrual period. Traditionally, the definition of prematurity was a birth weight of less than 2500 grams, regardless of gestational age.
Sudden infant death syndrome (SIDS)
The sudden death of an infant or young child which is unexpected by history and in which a thorough postmortem examination fails to demonstrate an adequate cause of death.
References:- Recommendations on SIDS
Tay-Sachs disease
An autosomal recessive disorder that reflects the deposition of ganglioside GM2 in the neurons of the central nervous system, owing to failure of lysosomal degradation.
Teratogen
Chemical, physical, and biologic agents that cause developmental anomalies.
TORCH
A complex of similar signs and symptoms produced by fetal or neonatal infection with a variety of microorganisms, including Toxoplasma gondii, rubella, cytomegalovirus, herpes simplex virus.
Trisomy
The presence in a somatic cell of one extra copy of a normally paired chromosome.
Turner syndrome
The spectrum of abnormalities that results from the presence of a complete or partial monosomy of the X chromosome in a phenotypic female.
X-linked disorder
Transmitted by genes on the X chromosome.