Clinical Correlations

Question 1

Split hand-foot malformations

Answer 1

• AKA: ectrodactylyl

Reduced number of digits and wide separation between anterior and posterior digits
- Mutations of at least 15 genes associated with split hand/split foot malformation

Common developmental pathway
- Disruption of middle portion of apical ectodermal ridge or its functions through various mechanisms late in limb formation

Question 2

Talipes equinovarus

Answer 2

• AKA clubfoot

Caused by persistent mechanical pressures of the uterine wall on the fetus
- Particularly in cases of ogliohydramnios

Question 3

Cleft lip

Answer 3

From lack of fusion of maxillary and nasomedial processes

In most complete form: entire premaxillary segment is separated from both maxillae
- Resulting bilateral clefts that run through lip and upper jaw between lateral incisors and the canine teeth

Question 4

Cleft palate

Answer 4

From incomplete or absent fusion of palatal shelves
- Usually multifactorial

Some chromosomal syndromes (trisomy 13) are characterized by high incidence of clefts
- Can be linked to chemical teratogen

Question 5

Holoprosencephaly

Answer 5

Broad spectrum of defects all based on defective formation of the forebrain and structures whose normal formation depends on influences from the forebrain

Present in up to 1/250 of all embryos and 1/10,000 live births

Arises in early pregnancy when forebrain is taking shape, and the brain defects usually involve archencephalic structures (olfactory system)

Question 6

Hypodontia

Answer 6

Congenital absence of teeth can be isolated or associated with certain genetic syndromes

Missing or malformed teeth, missing/sparse hair, absent/dysfunctional exocrine glands

Question 7

Hyperdontia

Answer 7

Excess number of teeth
- Isolated/associated with several genetic syndromes

Gain of function mutation –> supernumerary teeth and mandibular prognathism

Question 8

Microdontia

Answer 8

Small teeth (usually maxillary permanent lateral incisors

Question 9

Dentinogenesis imperfecta

Answer 9

Abnormalities of dentin –> appear blue-gray or amber brown; are opalescent

Question 10

Amelogenesis imperfecta

Answer 10

Group of clinically and genetically heterogeneous disorders that affect development of enamel

Result in abnormalities of the amount, composition, structure of enamel

Question 11

Heterotopic gastric mucosa

Answer 11

Heterotopic mucosa secretes hydrochloric acid, ulcers can form in unexpected locations

Question 12

Pyloric stenosis

Answer 12

Hypertrophy of the circular layer of smooth muscle that surrounds the pyloric end of the stomach

Causes a narrowing of the pyloric opening and impedes the passage of food

Question 13

Meckel’s diverticulum

Answer 13

blind pouch a few centimeters long located on the

antimesenteric border of the ileum about 50cm cranial from the ileocecal junction

Question 14

Volvulus

Answer 14

intestine rotates about vitelline artery and causes a condition known as volvulus

• can lead to strangulation of the bowel

Question 15

Vitelline fistula and duct cyst

Answer 15

persistent vitelline duct

constitutes a direct connection between the intestinal lumen and the outside of the body via the umbilicus.

Question 16

Hirschsprung’s disease

Answer 16

• aganglionic megacolon

manifested by great dilation of certain segments of the colon, is the absence of parasympathetic ganglia in the affected walls of the colon

Question 17

Imperforate anus

Answer 17

spectrum of anal defects that can range from a simple membrane covering the anal opening (persistence of the cloacal membrane) to atresia of various lengths of the anal canal, rectum, or both.

• missing anal opening

Question 18

Hindgut fistula

Answer 18

anal atresia is accompanied by a fistula linking the patent portion of the hindgut to another structure in the region of the original urogenital sinus region

Common types of fistulas connect the hindgut with the vagina, the urethra, or the bladder, and others may lead to the surface in the perineal area

Question 19

Failure of sternal fusion.

Answer 19

quantitatively minor defect in closure of throacic wall

Question 20

Tracheal or pulmonary agenesis.

Answer 20

Rare malformations that are incompatible with life

Tracheal agenesis: caused by defective septation between esophagus and the respiratory diverticulum

Pulmonary agenesis: primary consequence of mutation of FGF-10, likely that same malformation can result from null mutations or other key molecules involved in early branching morphogenesis of the lung buds

Question 21

Respiratory Distress Syndrome

Answer 21

Manifested in infants born prematurely
Characterized by labored breathing

Lungs underinflated and alveoli partially filled with proteinaceous fluid that forms a membrane over the respiratory surfaces
- Related to insufficiencies in formation of surfactant by type II alveolar cells

Question 22

congenital cysts in lung

Answer 22

Form in lung or other parts of respiratory tract
- Range from large single cysts to numerous small cysts located throughout the parenchyma of the lung

Associated with polycystic kidneys

Numerous cysts cause respiratory cysts

Question 23

Ectopia cordis.

Answer 23

Growth of two sides of thoracic wall severely defective

- Heart can form outside the thoracic cavity

Question 24

Diaphragmatic hernias.

Answer 24

Incomplete fusion of one or more of the components of the diaphragm can lead to open connection between abdominal and thoracic cavities

Question 25

Renal Agenesis

Answer 25

- unilateral or bilateral absence of any trace of kidney tissue - faulty inductive interaction between ureteric bud and metanephrogenic mesenchyme

Question 26

Potter Sequence

Answer 26

- in infants born with bilateral renal agenesis - flattened nose, wide interpupillary space, receding chin, tapering fingers, low-set ears, hip dislocation, pulmonary hypoplasia

Question 27

Renal Hypoplasia

Answer 27

one or both kidneys will be substantially smaller than normal even though degree of function may be retained

Question 28

Horshoe Kidney

Answer 28

kidneys are fused at their inferior poles

Question 29

Polycystic Kidney Disease

Answer 29

presence of hundreds of thousands of cysts of different sizes within the parenchyma of the kidney

Question 30

Exstrophy of the bladder

Answer 30

urinary bladder opens broadly onto abdominal wall

Question 31

Interatrial Septal Defects

Answer 31

- severe anatomical -- -- defect in interatrial septum result in persisting shunt between two atria most common: excessive resorption of tissue around foramen secundum or hypoplastic growth of septum secundum

Question 32

Interventricular Septal Defects

Answer 32

- most common congenital cardiac defect in infants, most defects close spontaneously before children are 10 yrs old - lesions associated with left-right acanotic shunting of blood flow

Question 33

Aortic and Pulmonary Stenosis

Answer 33

- septation of outflow tract by truncoconal ridges is asymmetrical, either aorta or pulmonary artery is abnormally narrowed - most severe: lumen of vessel essentially obliterated

Question 34

Tetralogy of Fallout

Answer 34

- lesion | - asymmetrical fusion of truncoconal ridges and malalignmnet of aortic/pulmonary valves

Question 35

Coarctation of Aorta

Answer 35

- common, nonlethal malformation of vascular system - either abrupt narrowing of descending aorta caudal to entrance of ductus arteriosus OR preductal coarctation (upstream from ductus)