Jeune syndrome, also known as asphyxiating thoracic dystrophy, is an inherited disorder of bone growth.
In some rare cases, retinal dystrophy may accompany respiratory manifestations causing a gradually deteriorating vision.
The commonest complication of Jeune syndrome is acute renal failure requiring either regular dialysis or transplant for survival. The ARF is usually due to bilateral microcystic renal disease which is an associated complication of Jeune syndrome, progressing to tubular atrophy and finally renal failure. Nephronopthisis may also occur.
Heart defects are rare but may occur, significantly increasing the mortality rate.
Liver and Pancreas
Retinal pigment degeneration and retinal dystrophy may occur leading to loss of vision.
The work up for Jeune syndrome entails the following main procedures:
A thorough and carefully conducted ultrasound antenatally may sometimes be enough to confirm diagnosis.
A complete physical examination may reveal a narrow, elongated, bell shaped chest and short arms and legs with a wineglass shaped pelvis. The infant may exhibit visible signs of respiratory distress like rapid, shallow and laborous breathing along with peripheral and central cyanosis.
Diagnosis is made based on imaging and radiological findings. Molecular testing confirms the disease. Ruling out thoracolaryngiopelvic dysplasia, Ellis-Van Creveld syndrome and Sensenbrenner syndrome is important.
Initially the infant has a narrow chest with a small ribcage and short limbs. The abnormally narrow chest restricts proper breathing which causes respiratory distress, peripheral cyanosis, dyspnea and tachypnea. Bones are short and weak with metaphyseal changes.
Jeune syndrome is a potentially lethal condition in which affected infants seldom reach their teens. If the syndrome is accompanied by its associated complications, commonly renal defects, the infant may not survive for more than a few months.
A number of genes have been implicated in the etiology of Jeune syndrome. One common factor of all mutated genes predisposing to this disease is the relation to cilia   . Based on the type of gene mutated, three subtypes are known:
This relatively uncommon subtype is caused by mutation in a gene of chromosome number 15, locus 15q13. The exact gene has not been pinpointed yet. However, it is considered that the gene involved is related with protein synthesis involved in the structure and/or functioning of cilia.
This is the commonest subtype, having a mutation in the intraflagellar transport 80 homolog (IFT80) gene on locus 3q25.33. IFT80 belongs to a family of genes called intraflagellar transport homologs. They serve to provide instructions about the synthesis of proteins required for the development of cilia. The transport of structures within the cilia and flagella is called the intraflagellar transport and is necessary for the normal functioning of these cellular projections. The protein synthesized under the instructions of this gene is called the IFT80 protein which is part of a much larger structure called IFT complex B. This complex plays a vital role in the movement and transfer of substances from the base to tip and vice versa within the cilia via intraflagellar transport. A mutation in the IFT80 gene thus produces a defective intraflagellar transport system which leads to non functional cilia (hence ATD is categorized as a primary ciliopathy). Three types of mutations are known to alter the IFT80 gene, two of which are point mutations while the third is a deletion of one amino acid.
Another subtype of Jeune syndrome occurs due to a mutation in the protein encoding dynein cytoplasmic 2, heavy chain 1 (DYNC2H1) located on locus 11q. This gene is also known by several other names such as ATD3, DHC2, DHC1b, DYH1b, hdhc11, SRPS2B, etc. This gene is involved in the synthesis of a large sized dynein protein, necessary for the smooth functioning of the intraflagellar transport due to its involvement in retrograde transport within the cilia. A mutation in DYNC2H1 results in defective working of the intraflagellar transport leading to immotile or nonfunctional cilia. The common type of mutation involved in the altered functioning of DYNC2H1 is splicing mutation.
Some other genes are also suspected in relation to Jeune syndrome. These include WDR19 (4p14) and TTC21B (2q24.3).
Jeune syndrome is an extremely rare genetic disease having an incidence of 1:100,000-130,000 live births in the United States. Exact prevalence is unknown but an annual incidence is estimated to be 1-5 cases among 500,000 births.
Jeune syndrome does not have any prevalence in a particular race.
Age of onset is neonatal. The disease can be be diagnosed in the antenatal period as well as postnatally.
It does not have any association with sex type.
The pattern of inheritance is autosomal recessive. As a result of mutations in the genes encoding the proteins involved in intraflagellar transport, the cilia developed are partially or completely immotile and/or nonfunctional. These abnormal cilia occur on many different cell surfaces but the exact mechanism by which the ciliopathy leads to bone disorders and respiratory symptoms is heretofore unknown. Several other systemic manifestations like retinal dystrophy, pancreatic cysts and liver fibrosis occur in rare cases but their direct or indirect association with the ciliopathy is also not clear.
Once the mutation is established, the bone growth is stunted. Both upper and lower limbs have abnormally short bones but the most serious manifestation of this syndrome is apparent in the thoracic cavity. All 12 pairs of ribs plus their respective costal cartilages are present but are extremely small in length, exhibiting short-rib dysplasia. The thoracic cavity itself is very narrow and sometimes elongated. The small chest restricts the normal growth of lungs and the bronchial tree causing pulmonary hypoplasia. Expansion of lungs is limited so breathing is difficult and laborous. The infant usually breaths in short, rapid, shallow inhales and exhales, showing visible discomfort.
Breathing problems vary in severity. In about 60-70% of cases the affected infant usually dies of respiratory failure. In some cases the affected children reach adolescence while in some very rare cases reach adulthood with only symptoms of mild breathing disorder like occasional dyspnea and tachypnea. The abdominal cavity, head and neck are usually normal.
Jeune syndrome is a rare ciliopathy which causes a bone growth disorder. Also known as asphyxiating thoracic dystrophy (ATD), this syndrome presents with characteristic findings like short-ribs dysplasia, abnormally narrow thorax, short limbs and other skeletal abnormalities. The resultant congenital dwarfism is clearly apparent in infancy. Major symptoms include a small, narrow chest with restrictive respiratory movements and incomplete lung growth. Hands and legs are short with stubby fingers, sometimes having more than five digits. The acetabula have a characteristic 'trident' appearance and metaphyseal changes are evident.
First described by Jeune in 1955 on a pair of siblings having congenital dwarfism with narrow chests, this syndrome has been studied in detail and a set of classical findings has been discovered helping in its diagnosis . Other names of this disease include chondroectodermal dysplasia like syndrome and infantile thoracic dystrophy.
It is of three main types depending upon the type of gene mutated. All types are inherited from parents to offsprings if both parents have one copy of the mutated gene.
Signs and symptoms
It can be easily prevented with proper counselling and support
It does not have a cure. Treatment is symptomatic.
Jeune syndrome is a genetic disease caused by mutations. The resultant effects include several manifestations which mostly lead to death of the child in 60-70% cases. The disease presents at birth and persists for life and is incurable. However, the disease is easily preventable by genetic counselling and guidance.
Jeune syndrome is a very rare but potentially lethal congenital anomaly caused by mutations in IFT80 genes, among others. It is a ciliopathy causing bone defects, pulmonary hypoplasia and renal defects.