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Achondrogenesis type 2(ACG2)

MedGen UID:
66315
Concept ID:
C0220685
Congenital Abnormality
Synonyms: ACG2; Achondrogenesis, Langer-Saldino type; ACHONDROGENESIS, TYPE IB; ACHONDROGENESIS, TYPE II; Chondrogenesis imperfecta; hypochondrogenesis; Langer-Saldino achondrogenesis
Modes of inheritance:
Autosomal dominant inheritance
MedGen UID:
141047
Concept ID:
C0443147
Intellectual Product
Autosomal dominant inheritance refers to genetic conditions that occur when a mutation is present in one copy of a given gene (i.e., the person is heterozygous).
SNOMED CT: Achondrogenesis, type II (254061001); Langer-Saldino dysplasia (254061001); Langer-Saldino achondrogenesis (254061001)
 
Gene: COL2A1
Cytogenetic location: 12q13.11
OMIM: 200610

Definition

Achondrogenesis type II is characterized by severe micromelic dwarfism with small chest and prominent abdomen, incomplete ossification of the vertebral bodies, and disorganization of the costochondral junction. This form is an autosomal dominant trait occurring mostly as new mutations. However, somatic and germline mosaicism have been reported (summary by Comstock et al., 2010). [from OMIM]

Additional description

From GHR
Hypochondrogenesis is a rare, severe disorder of bone growth. This condition is characterized by a small body, short limbs, and abnormal bone formation (ossification) in the spine and pelvis. Affected infants have short arms and legs, a small chest with short ribs, and underdeveloped lungs. Bones in the skull develop normally, but the bones of the spine (vertebrae) and pelvis do not harden (ossify) properly. The face appears flat and oval-shaped, with widely spaced eyes, a small chin, and, in some cases, an opening in the roof of the mouth called a cleft palate. Individuals with hypochondrogenesis have an enlarged abdomen and may have a condition called hydrops fetalis in which excess fluid builds up in the body before birth. As a result of these serious health problems, some affected fetuses do not survive to term. Infants born with hypochondrogenesis usually die at birth or shortly thereafter from respiratory failure. Babies who live past the newborn period are usually reclassified as having spondyloepiphyseal dysplasia congenita, a related but milder disorder that similarly affects bone development.  http://ghr.nlm.nih.gov/condition/hypochondrogenesis

Clinical features

Thickened nuchal skin fold
MedGen UID:
504456
Concept ID:
CN000442
Finding
A thickening of the skin thickness in the posterior aspect of the fetal neck. A nuchal fold measurement is obtained in a transverse section of the fetal head at the level of the cavum septum pellucidum and thalami, angled posteriorly to include the cerebellum. The measurement is taken from the outer edge of the occiput bone to the outer skin limit directly in the midline. A measurement 6 mm or more is considered significant between 18 and 24 weeks and a measurement of 5 mm or more is considered significant at 16 to 18 weeks (pmid:16100637).
Cystic hygroma
MedGen UID:
427823
Concept ID:
CN000444
Finding
A cystic lymphatic lesion of the `neck` (FMA:7155).
Frontal bossing
MedGen UID:
505049
Concept ID:
CN001816
Finding
Bilateral bulging of the lateral frontal bone prominences with relative sparing of the midline.
Short nose
MedGen UID:
505478
Concept ID:
CN002885
Finding
Distance from nasion to subnasale more than two standard deviations below the mean, or alternatively, an apparently decreased length from the nasal root to the nasal tip.
Short ribs
MedGen UID:
500894
Concept ID:
CN000727
Finding
Reduced rib length.
Narrow chest
MedGen UID:
504594
Concept ID:
CN000728
Finding
Reduced width of the chest from side to side, associated with a reduced distance from the sternal notch to the tip of the shoulder.
Horizontal ribs
MedGen UID:
504642
Concept ID:
CN000833
Finding
A horizontal (flat) conformation of the ribs, the long curved bones that form the rib cage and normally progressively oblique (slanted) from ribs 1 through 9, then less slanted through rib 12.
Postaxial hand polydactyly
MedGen UID:
427858
Concept ID:
CN001092
Finding
Supernumerary digits located at the ulnar side of the hand (that is, on the side with the fifth finger).
Abnormality of the foot
MedGen UID:
427893
Concept ID:
CN001600
Finding
An abnormality of the `skeleton of foot` (FMA:24222).
Frontal bossing
MedGen UID:
505049
Concept ID:
CN001816
Finding
Bilateral bulging of the lateral frontal bone prominences with relative sparing of the midline.
Skeletal dysplasia
MedGen UID:
505316
Concept ID:
CN002411
Finding
A general term describing features characterized by abnormal development of bones and connective tissues.
Micromelia
MedGen UID:
505428
Concept ID:
CN002699
Finding
The presence of abnormally small extremities.
Disproportionate short-trunk short stature
MedGen UID:
500958
Concept ID:
CN003177
Finding
A type of `disproportionate short stature` (HP:0003498) characterized by a short trunk but a average-sized limbs.
Abnormality of bone mineral density
MedGen UID:
428073
Concept ID:
CN003849
Finding
This term applies to all changes in bone mineral density which (depending on severity) can be seen on x-rays as a change in density and or structure of the bone. Changes may affect all bones of the organism, just certain bones or only parts of bones and include decreased mineralisation as may be seen in osteoporosis or increased mineralisation and or ossification as in osteopetrosis, exostoses or any kind of atopic calicfications of different origin and distribution. The overall amount of mineralization of the bone-organ can be measured as the amount of matter per cubic centimeter of bones, usually measured by densitometry of the lumbar spine or hip. The measurements are usually reported as g/cm3 or as a Z-score (the number of standard deviations above or below the mean for the patient's age and sex). Note that measurement with this method does not reflect local changes in other bones, and as such might not be correct with regard the hole bone-organ.
Broad long bones
MedGen UID:
446679
Concept ID:
CN004979
Finding
Increased cross-section (diameter) of the long bones. Note that widening may primarily affect specific regions of long bones (e.g., diaphysis or metaphysis), but this should be coded separately.
Thickened nuchal skin fold
MedGen UID:
504456
Concept ID:
CN000442
Finding
A thickening of the skin thickness in the posterior aspect of the fetal neck. A nuchal fold measurement is obtained in a transverse section of the fetal head at the level of the cavum septum pellucidum and thalami, angled posteriorly to include the cerebellum. The measurement is taken from the outer edge of the occiput bone to the outer skin limit directly in the midline. A measurement 6 mm or more is considered significant between 18 and 24 weeks and a measurement of 5 mm or more is considered significant at 16 to 18 weeks (pmid:16100637).
Polyhydramnios
MedGen UID:
504854
Concept ID:
CN001423
Finding
The presence of excess amniotic fluid in the uterus during pregnancy.
Hydrops fetalis
MedGen UID:
504951
Concept ID:
CN001623
Finding
The abnormal accumulation of fluid in two or more fetal compartments, including ascites, pleural effusion, pericardial effusion, and skin edema.
Abdominal distention
MedGen UID:
34
Concept ID:
C0000731
Finding
Swelling of the abdomen resulting from excessive food intake, malnutrition, liver disease, primary abdominal tumors, and tumors metastatic to the abdominal cavity.
Disproportionate short-trunk short stature
MedGen UID:
500958
Concept ID:
CN003177
Finding
A type of `disproportionate short stature` (HP:0003498) characterized by a short trunk but a average-sized limbs.
Disproportionate short-limb short stature
MedGen UID:
426028
Concept ID:
CN007806
Finding
A type of `disproportionate short stature` (HP:0003498) characterized by a short limbs but an average-sized trunk.
Malformation of the heart and great vessels
MedGen UID:
428300
Concept ID:
CN002327
Finding
Congenital malformation of the heart or great vessels (i.e., the large blood vesslesentering and leaving the heart: aorta, the pulmonary arteries and veins, and the superior and inferior vena cava).
Edema
MedGen UID:
504667
Concept ID:
CN000907
Finding
An abnormal accumulation of fluid beneath the skin, or in one or more cavities of the body.
Hydrops fetalis
MedGen UID:
504951
Concept ID:
CN001623
Finding
The abnormal accumulation of fluid in two or more fetal compartments, including ascites, pleural effusion, pericardial effusion, and skin edema.

Recent clinical studies

Etiology

Weisman PS, Kashireddy PV, Ernst LM
Pediatr Dev Pathol 2014 Jan-Feb;17(1):10-20. Epub 2013 Oct 21 doi: 10.2350/13-02-1305-OA.1. [Epub ahead of print] PMID: 24144387
Soothill PW, Vuthiwong C, Rees H
Prenat Diagn 1993 Jun;13(6):523-8. PMID: 8372079

Diagnosis

Weisman PS, Kashireddy PV, Ernst LM
Pediatr Dev Pathol 2014 Jan-Feb;17(1):10-20. Epub 2013 Oct 21 doi: 10.2350/13-02-1305-OA.1. [Epub ahead of print] PMID: 24144387
Soothill PW, Vuthiwong C, Rees H
Prenat Diagn 1993 Jun;13(6):523-8. PMID: 8372079
Moerman P, Fryns JP, Goddeeris P, Lauweryns JM
Arch Pathol Lab Med 1982 Nov;106(12):635-40. PMID: 6897172
Dorfman HD, Lorenzo J
Skeletal Radiol 1980;5(3):189-92. PMID: 6970987
Macpherson RI, Wood BP
Pediatr Radiol 1980 Jul;9(4):217-24. PMID: 6773018

Recent systematic reviews

Weisman PS, Kashireddy PV, Ernst LM
Pediatr Dev Pathol 2014 Jan-Feb;17(1):10-20. Epub 2013 Oct 21 doi: 10.2350/13-02-1305-OA.1. [Epub ahead of print] PMID: 24144387

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