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    Achondrogenesis (Hypochondrogenesis)

    Achondrogenesis type I[1]

    Achondrogenesis describes a rare group of lethal skeletal dysplasias. Currently, 3 variants have been defined: type 1A (Houston-Harris), type 1B (Parenti-Fraccaro), and type 2 (Langer-Saldino).

    This disorder is related to the following process: congenital.


    In patients with achondrogenesis, prenatal history may include any of the following: Breech presentation, hydrops and polyhydraminos [8].

    Presentation for achondrogenesis type I

    • There is lethal neonatal dwarfism with a mean birth weight of 1200 g.
    • Head is disproportionately large, the skull is soft, the forehead is sloping, the facial plane is convex, there is a flat nasal bridge and a host of other craniofacial defects.
    • The neck is extremely short.
    • There is lung hypoplasia and short and barrel-shaped thorax.
    • There is ventricular septal defect, patent ductus arteriosus and atrial septal defect.
    • The abdomen is protuberant.
    • Micromelia (extremely short limbs is noted) and it is shorter than what is seen in type II achondrogenesis. The appendages are flipper like as well.

    Presentation for achondrogenesis type II

    • There is lethal neonathal dwarfism but the mean birth weight is 2100 g.
    • Craniofacial features include a large a head, very large forehead, flat facial plane, flat nasal bridge, small nose with a severely anteverted nostrils, there is normal philtrium in most cases as well as micrognathia. 
    • The neck is extremely short.
    • There is lung hypoplasia, bell shaped cage and a short and flared thorax.
    • Limbs are short.

    Entire body system
    • Because of the defect, GMAP-210 is not able to move the proteins, and they remain in the endoplasmic reticulum, which swells up.[]
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  • neurologic
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  • respiratoric
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  • musculoskeletal
    • Figure 2: Post mortem baby gram showing delayed ossification of sacral bones, short trunk, macrocephaly and extremely short long bones.[]
    • Additional sonographic findings include: micrognathia macrocephaly frontal bossing flat face anteverted nares long philtrum narrow fetal thorax lung aplasia / hypoplasia rib fractures may be present in type 1A Other ancillary sonographic features that[]
    Trunk Shortness
    • Macroscopical synopsis large head short trunk severe micromelia no ossification of vertebra, ischial and pubic bones severe micromelic dwarfism cleft palate cystic hygroma barrel-shaped chest short trunk short ribs horizontal ribs normal clavicles distended[]
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  • Workup

    The molecular studies for achondrogenesis are performed on EDTA-anticoaagulated blood for DNA analysis [9].

    With mutation analysis of the DDST gene, the following is identified: point mutations, deletions leading to premature stop codons, substitutions and deletions of amino acids within transmembrane domains, presumed mutations lying outside the coding region but causing low mRNA levels and substitutions of amino acids in intracellular or extracellular domains.

    Radiological features often vary and no single feature is obligatory. It is not always possible to differentiate between type 1A and type 1B on radiographs. The degree is ossification is dependent of age and caution is needed radiograph comparisons at different stages of gestation.

    Bone and cartilage tissues should be obtained for use in histological and biochemical studies.


    There is presently no treatment for the underlying disorder and so medical care is supportive [10].


    The outcome is often very negative. Majority of infants diagnosed with achondrogenesis are either stillborn or die shortly after birth due to the breathing problems that come with an abnormally small chest [7].


    • Researchers have described at least three forms of achondrogenesis, designated as Achondrogenesis type 1A, achondrogenesis type 1B and achondrogenesis type 2.[]
    • […] produce achondrogenesis type II/hypochondrogenesis. ( 10797431 ) Koerkkoe J....Prockop D.J. 2000 20 Achondrogenesis type II (Langer-Saldino achondrogenesis): a case report. ( 11069003 ) Lee H.S....Chi J.G. 2000 21 A case of achondrogenesis type II associated[]
    • What is Developmental Bone Birth Defect (Achondrogenesis) Statistics on Developmental Bone Birth Defect (Achondrogenesis) Risk Factors for Developmental Bone Birth Defect (Achondrogenesis) Progression of Developmental Bone Birth Defect (Achondrogenesis[]
    • Achondrogenesis Type 1B Achondrogenesis type 1B is similar to achondrogenesis type 1A, and can be differentiated on a genetic test.[]
    • Prevalence and incidence statistics for Achondrogenesis: See also prevalence and incidence page for Achondrogenesis Prevalance of Achondrogenesis: 1 per 40,000 - 60,000 people are affected by achondrogenesis type 2 and hypochondrogenesis, Genetics Home[]
    Achondrogenesis Type 2
    • Home List of Disease Achondrogenesis type 2 Disease Name : Achondrogenesis type 2 Alternate Names : null Virus Name : will be updated soon Treatment : will be updated soon Description : Infants with achondrogenesis, type 2 have short arms and legs, a[]
    • Achondrogenesis type 2 is considered an autosomal dominant disorder.[]
    • Achondrogenesis, type 2 is a subtype of collagenopathy, types II and XI.[]
    • Achondrogenesis type 2 is one of several skeletal disorders that result from mutations in the COL2A1 gene.[]
    • Researchers have described at least three forms of achondrogenesis, designated as Achondrogenesis type 1A, achondrogenesis type 1B and achondrogenesis type 2.[]
    • Redundant soft tissues with subcutaneous edema ( hydrops ).[]
    • There was a large cystic hygroma measuring 5.4 4.7 2.7 cm, with marked generalised soft tissue edema.[]
    • Langer-Saldino). ( 8375887 ) Reddeppa T....Divekar D.S. 1993 42 Collagen type II in Langer-Saldino achondrogenesis: absence of major abnormalities in a less severe case. ( 1515761 ) BAotge B....MA1ller P.K. 1992 43 Transvaginal ultrasound recognition of nuchal edema[]
    • There was evidence of cystic hygroma and hydrops fetalis (extensive skin edema and mild plural effusion).[]
    • Lack of vertebral ossification is important as a means of differentiating achondrogenesis, of either type I or type II, from other lethal dysplasias with similar features,including short rib-polydactyly syndromes and thanatophoric dysplasia.[]
    • […] morphologic, biochemical and molecular analysis of a case of achondrogenesis type II resulting from substitution for a glycine residue (Gly691-- Arg) in the type II collagen trimer. ( 7757081 ) Mortier G.R....Cohn D.H. 1995 30 Achondrogenesis type II with polydactyly[]
    Respiratory Failure
    • As a result of their serious health problems, infants with achondrogenesis are usually born prematurely, are stillborn, or die shortly after birth from respiratory failure.[]
    • As a result of their serious health problems, infants with achondrogenesis are usually born prematurely , are stillborn , or die shortly after birth from respiratory failure.[]
    • As a result of serious health problems, infants with achondrogenesis usually die before birth, are stillborn, or die soon after birth from respiratory failure.[]
    • The health problems associated with these conditions are life-threatening and most affected infants die before birth, are stillborn or die shortly after birth of respiratory failure.[]
    Skeletal Dysplasia
    • Forms and Documents Test Details Genes: COL2A1, SLC26A2, TRIP11 Clinical Utility: Diagnosis in a patient based on clinical or radiographic findings suggestive of a skeletal dysplasia Diagnosis for known familial pathogenic variant(s) Distinguish between[]
    • Achondrogenesis is a severe skeletal dysplasia that is invariably lethal before or after birth.[]
    • Fetal skeletal dysplasias, sonographic indices associated with adverse outcomes.[]
    • The ultrasound findings of lethal skeletal dysplasia, with severe under‐ossification of the vertebral bodies and normal hands, are diagnostic for this condition.[]
    • This is also very common with a child that's diagnosed with Skeletal Dysplasia.[]
    • References 107 Examination of the Fetus and Placenta 126 References 148 xiii 151 The Baby with Malformations 165 Causes of Perinatal Death 178 Maternal and Environmental Factors Associated with Perinatal Death 184 Pathological Findings in Macerated Stillbirths[]
    • Infants born with achondrogenesis have severe health problems thus they are born prematurely or as stillbirth .[]
    • Increased incidence of prematurity and stillbirth.[]
    • Mortality/Morbidity: Achondrogenesis type I results in stillbirth more frequently than type II.[]
    • Compared with type I, achondrogenesis type II is characterized by fewer stillbirths, longer survival, longer gestation period, less severe micromelia, a very peculiar crescent-shaped inner and inferior margins of the iliac bones, and characteristic craniofacial[]
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  • Etiology

    The disorder is an inherited one which means it is passed down through families. Some of them are recessive meaning that both parents carry the defective gene and in such a situation, the chance of the subsequent child to be affected by the condition is about 25% [4].

    To differentiate them, type 1a is autosomal recessive disorder with a chromosomal locus that is unknown. Type 1b is an autosomal recessive disorder which arises from mutations of the diastrophic dysplasia sulfate transporter gene found at 5q32-q33. Type 2 achondrogenesis on the other hand, is an autosomal dominant type 2 collagenopathy which arises from mutations in the COL2A1 gene. It is located at 12q13.1-q13.3.


    Types 1 and 2 lethal achondrogenesis are both rare. The respective frequencies are not known but the overall frequency has been placed at 1 per 40,000 births [2].

    With achondrogenesis type 1, the number of still births is higher than achondrogenesis type II. For babies who have achondrogenesis type 1 the gestation period is shorter and they survive for a shorter period than those who have type II. Their limbs are also much shorter and this buttresses the point that type 1 achondrogenesis is the more severe form.

    There is no racial predilection with achondrogenesis and males and females are affected equally. All cases of achondrogenesis are detected at birth and so there is no age difference.

    Sex distribution
    Age distribution


    In patients with achondrogenesis type 1B, a series of mutations in the DDST gene has been identified. Achondrogenesis type 1B is associated with the homozygosity and heterozygosity for these mutations. The mutation leads to structural mutations in the transmembrane domains and premature stop codons.
    Diastrophic dysplasia with less severe phenotypes or type II atelosteogenesis arises when regulatory mutation is caused by extracellular loops, low messenger RNA (mRNA levels) or cytoplasmic tail mutations. The skin fibroblasts and chondrocytes from patients with the type 1B are not able to incorporate exogenous sulfate when cultured [5].

    Type 2 achondrogenesis and other collagenopathies like spondyloepiphyseal dysplasias and hypochondrogensis are caused by different mutations in the gene which encodes type II collagen (COL2A1). Type 2 has a single base change serine is replaced by glycine within the procollagen gene of the alpha 1(II) chain. This brings about a disruption in the triple helix formation thereby leading to a paucity of type II collagen in the matrix of the cartilage. Apart from skeletal abnormalities, severe pulmonary hypoplasia which is believed to be related directly to the underlying pathology in the expression of collagen, is linked with achondrogenesis [6].

    The Whitely and Gorlin prototype 4 (type II achondrogenesis/hypochondrogenesis show immmunohistolgic findings which show an evident abnormal intracellular accumulation of type II collagen within vacuolar structures of chondrocytes. This suggests the presence of poorly secreted and abnormal collagen. The observed phenotype is as a result of the molecular defects of type II collagen and new dominant mutations.


    This condition can only be prevented with the help of accurate genetic counseling. For the genetic counseling to be effective however, the types of achondrogenesis in both parents must be properly established [11].


    Achondrogensis is a collection of a number of disorders which are the severest forms of congenital chondrodysplasia. The major characteristics of the conditions are skeletal deformities usually depicted by shortened limbs and a generally small body. Infants born with achondrogenesis have severe health problems thus they are born prematurely or as stillbirth. Of the number that survives past the birth stage, majority die of respiratory problems. Some of the infants however, have gone on to live longer with the aid of intensive medical care [1].

    According to research, there are three forms of achondrogenesis. They are: achondrogeneis type 1A, achondrogenesis type 1B and achondrogenesis type 2. The various types are differentiated by the signs and symptoms, pattern of inheritance and genetic cause. There is possibility of the existence of other types of achondrogenesis but these have not been characterized as their cause has not been documented.

    Type 1A of achondrogenesis is caused when there is a defect in the microtubules of the Golgi apparatus. A nonsense mutation in the thyroid hormone receptor interactor 11 gene (Trip11), which encodes the Golgi microtubule-associated protein 210 (GMAP-210), showed defects that are similar to this disease in mice [3].

    Human patients with achondrogenesis type 1A also had a loss of function mutations in GMAP-210 when their DNA was sequenced. GMAP-210 is responsible for the movement of proteins from the endoplasmic reticulum to the Golgi apparatus but with this defect, it is unable to do so and therefore the proteins remain in endoplasmic reticulum causing it to become swollen. With the loss of the Golgi apparatus, the functions of certain cells are affected but the cells affecting the formation of bones and cartilages are the most affected.

    A similar mutation in SLC26A2 (responsible for the encoding of a sulfate transporter) is what causes achondrogenesis type 1B.

    Patient Information

    This condition is often diagnosed at birth even when the child is stillbirth. This is where medical care comes in. As a parent of such a child however, you need to bear in mind that the chances of the child surviving beyond early infancy is very low. Therefore, effort must be put into ensuring that you are ready for whatever happens next by enrolling into a support group. Most importantly, your focus should be on ensuring that there is no repetition by going for genetic counseling and constant medical checks before and immediately after conception is confirmed.


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    3. Lethal skeletal dysplasia in mice and humans lacking the GolginGMAP-210, Patrick Smits, N Engl J Med, 362:206, Jan. 21, 2010
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    7. Spranger J, Winterpacht A, Zabel B. The type II collagenopathies: a spectrum of chondrodysplasias. Eur J Pediatr. Feb 1994;153(2):56-65.
    8. Freisinger P, Bonaventure J, Stoess H, Pontz BF, Emmrich P, Nerlich A. Type II collagenopathies: are there additional family members?. Am J Med Genet. May 3 1996;63(1):137-43
    9. Stillbirth Collaborative Research Network Writing Group. Association between stillbirth and risk factors known at pregnancy confirmation. JAMA 2011; 306:2469.
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    11. Hall JG. Review and hypotheses: somatic mosaicism: observations related to clinical genetics. Am J Hum Genet. Oct 1988;43(4):355-63

    • A case of lethal congenital dwarfism with accelerated skeletal maturation - S Blomstrand, I Claësson, J Säve-Söderbergh - Pediatric radiology, 1985 - Springer
    • Achondrogenesis type II (Langer–Saldino) in association with jugular lymphatic obstruction sequence - KD Wenstrom, RA Williamson, WW Hoover - Prenatal , 1989 - Wiley Online Library
    • A genetic approach to the diagnosis of skeletal dysplasia - S Unger - Clinical orthopaedics and related research, 2002 -
    • A severe autosomal recessive acromesomelic dysplasia, the Hunter-Thompson type, and comparison with the Grebe type - LO Langer, J Cervenka, M Camargo - Human genetics, 1989 - Springer
    • A Case of Recurrent Craniopharyngioma - G Gayen, NC Mahapatra - 30th WB State PEDICON 2011, 2011 -

    Media References

    1. Achondrogenesis type I, CC BY 2.0