What Is Thanatophoric Dysplasia?
Thanatophoric dysplasia is a severe form of dwarfism that affects the length of the arms and legs. Moreover, there are other abnormalities, such as an extra fold of skin on the limbs along with the short ribs and misproportion of the head and facial features.
This genetic skeletal abnormality is usually divided into two different types.
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Type 1- Shows symptoms like curved thigh bones and a flat spinal cord.
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Type 2- Shows symptoms such as straight thigh bones with the front and both sides of the skull extended abnormally, making it look abnormally large and odd-shaped.
As the disorder is very rare and only recorded in one in 50,000 cases, the prognosis of the syndrome is very poor, as most of the infants born with this condition die shortly after birth.
What Are the Causes of Thanatophoric Dysplasia?
The condition is primarily caused by a genetic mutation in infants. The gene responsible for the abnormality is essential for regulating the protein, which in turn is important for brain and bone development. The abnormality or mutation in the gene causes the overactivation of the gene, which leads to deformity and disturbance related to bone development. The over-activation of the genes is called a “gain-of-function” mutation.
The disorder is also known to be autosomal dominant, which means the gene is located on any chromosome except the sex chromosomes. The dominant genes are the ones that have only one copy of the mutated gene for an infant to have the disease.
What Are the Signs and Symptoms of Thanatophoric Dysplasia?
This genetic mutation affects multiple systems and causes the following symptoms:
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Dermatological or Skin:
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Acanthosis Nigricans: Acanthosis nigricans is a comparatively rare symptom associated with the syndrome, where the part of the neck shows hyperpigmented plaque formation.
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Facial:
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Depressed Nasal Bridge: It is the classic sign of the disorder where the child has a flat nose.
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Flat Face: It is one of the very distinctive and frequent symptoms associated with this disorder, in which the absence of concavity or convexity of the face gives it a flat appearance.
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Decreased Midface Size: The condition shows an underdeveloped face with increased concavity of the face, decreased nasolabial angle, or vertical shortening of the infraorbital and perihilar regions.
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Musculoskeletal:
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Abnormal Metaphysis: Metaphysis is the area where the epiphysis attaches to the diaphysis. This disorder shows the involvement of one or more metaphyses with the abnormality.
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Macrocephaly: The children with macrocephaly condition show an abnormally large occipitofrontal (head) circumference.
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Low Muscle Tone: The abnormally low muscle tone is also known as hypotonia. The muscles in the body have some partial passive movements, even in a state of relaxation. This gives resistance to the passive stretching of the muscles. In the condition of hypotonia, the muscles of the body lose their resistance to passive stretching.
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Cloverleaf Skull: Children with the disorder occasionally show this symptom. The symptoms have multiple fused sutures (joints) of the skull bones during the developmental phase causing the trilobar (appearance of having three lobes) skull shape.
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Altered Sacroiliac Joint: The sacroiliac joint is the attachment between the spine and the hip bone. The disorder represents the abnormality of the bone.
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Kyphosis: Kyphosis is the condition that shows the increased front-to-back curve of the upper spine.
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Hyperflexible Joints: It is a condition caused by increased flexibility and mobility of muscles and ligaments of the body.
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Hip Dysplasia: The disorder is associated with abnormally overgrown congenital cell formation seen in the hip area.
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Growth and Development:
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Very Short Limbs: Children with this condition show abnormally short limbs.
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Narrow Chest: The physical examination of the newborn shows reduced distance from the sternal notch to the tip of the shoulder. An abnormally narrow chest is another classic sign of the disorder.
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Underdeveloped Lungs: This is the most frequent condition associated with the syndrome. It is also known as pulmonary hypoplasia, where the development of the lung is inhibited by the condition.
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Deafness: Children with thanatophoric dysplasia are often seen with this disability due to decreased magnitude of sensory perception of sound.
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Brachydactyly: It is the condition where the digits appear distinctively short.
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Bulging Eyes: With this syndrome, the eyes seem to be abnormally protruded in appearance.
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Prenatal Growth Deficiency: The mutation of the genes hinder the embryonic development of the fetus that shows abnormal signs and symptoms of the disease or syndrome.
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Kidney Abnormalities: It is a rare condition associated with the syndrome. However, the abnormality of the kidneys can create a new set of complications in children.
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Cardiovascular:
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Respiratory Insufficiency: The structural abnormality of the heart and the vessels leads to cardiovascular malformation in children that creates respiratory insufficiency.
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Neurological or Brain:
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Hydrocephalus: Hydrocephalus is the complication associated with the disorder, where there is over-accumulation of the fluid seen in the ventricles of the brain. Although it is the occasional symptom seen in children, the condition can cause many complications related to it. For instance, the condition can cause an extra buildup of pressure inside the brain, causing damage to brain activity.
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How to Diagnose Thanatophoric Dysplasia?
There are several ways to diagnose the condition, such as:
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Prenatal Ultrasonography: Usually, if the mother is regularly going with ultrasonography during the second and third trimester, most of the fatal conditions related to the fetus can be revealed. Sometimes, some of the disorders are slightly difficult to diagnose because of their prevalence. Ultrasonography can diagnose the symptoms of the disorder, such as macrocephaly, cloverleaf-shaped skull, ossification of the spine and skull, and abnormally narrow chest cavity.
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Postnatal Examination: As thanatophoric dysplasia represents many easily recognizable symptoms, the postnatal physical examination can be very useful in diagnosing the condition.
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Radiographs: The radiographs show very distinctive abnormalities associated with the syndrome. For instance, the syndrome shows an abnormally narrow thorax, and the ribs appear wide and cupped. The lumbar spine appears flat with vertebral bodies. Above all, the most distinctive feature the radiograph shows is the oddly short phalanges (finger bones), metacarpals (tubular bones between wrist and forelimb), and metatarsals (forefoot bones).
How to Treat Thanatophoric Dysplasia?
Due to its severity and involvement in the bony structure of infants, there is no particular cure for this condition. However, the symptoms and signs can be managed with regular follow-up visits. To commence with, pediatricians usually do not suggest vaginal birth in the prenatally diagnosed condition. Also, the very frequent fatal complication newborns are born with is respiratory insufficiency.
Owing to this life-threatening condition, newborns do not live for long. Newborns with the same complication immediately require respiratory support. Additionally, pediatricians can recommend drug therapy, such as antiepileptic drugs, and surgical treatment, such as the placement of shunts to drain excess fluid from the brain.
In the end, due to multi-organ involvement and the severity and progress of the disease, the pediatrician regularly recommends the parents come for follow-up visits.
Conclusion:
Thanatophoric dysplasia is a congenital disorder that is very difficult to manage emotionally for parents and physically for newborns. As the syndrome has a very poor prognosis, the condition requires a great deal of constant medical care. As thanatophoric dysplasia represents myriad and multifaceted fatal symptoms, pediatricians usually suggest terminating the pregnancy if it is diagnosed earlier. On the other hand, in newborns, clinical procedures, diet management, and physical and occupational therapy can help to manage the symptoms.
