Introduction:
In 2001, Valérie Cormier-Daire et al. described a new skeletal dysplasia disorder (the abnormal organization of cells in the tissues or inside the organ) that showed immense resemblance to a life-threatening condition called Achondrogenesis. This novel condition seemed to have distinct radiographic and histomorphologic features distinguishing it from other skeletal dysplasia disorders. This condition was named Baby Rattle pelvis dysplasia based on the radiographic findings of the reported patient's hipbone resembling a baby rattle appearance. This article will discuss Baby rattle pelvic dysplasia condition in detail.
What Is Baby Rattle Pelvic Dysplasia?
Baby rattle pelvic dysplasia is a deadly skeletal dysplasia condition. This condition was newly described with distinguishable radiographic and histomorphologic features differentiating them from others. It is believed to be a genetic condition critically affecting the cartilage and bone development in the unborn fetus. The typical features of the condition are the bifid humerus (skeletal abnormality with the tubular bone of the arm), lack of ossification (the process of bone formation) in the vertebral column, and the unique baby rattles resemblance of the hip morphology.
What is Achondrogenesis?
Achondrogenesis is a lethal skeletal dysplasia referring to a group of disorders characterized by extreme shortening of the upper and lower limbs, developmental deformities of the ribcage and vertebra, and various skeletal disorders. It is a genetic condition inherited in both autosomal dominant and autosomal recessive patterns. There are three types of Achondrogenesis based on the genetic abnormalities of the patient namely Achondrogenesis type 1A, Achondrogenesis type 1B, and Achondrogenesis type 2. They are usually diagnosed during pregnancy through prenatal examination by ultrasound (a method of investigation that uses high-intensity sound waves to produce pictures of internal structures).
What Are the Clinical Manifestations of Baby Rattle Pelvic Dysplasia?
The signs and symptoms of Baby rattle pelvic dysplasia can be noted during pregnancy through ultrasound examination. The clinical manifestations of the Baby rattle pelvic dysplasia mentioned below are based on the case reported on a 28-year-old woman of 32 weeks gestation.
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Polyhydramnios: A condition characterized by excessive accumulation of amniotic fluid around the baby in the uterus during pregnancy.
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Dwarfism: A condition with a severe decrease in the individual's stature. Shortened upper and lower extremities compared to the trunk of the baby.
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Cerebro-Ventriculomegaly: A condition in which there is an enlargement of the brain's ventricles (communicating network of cavities that are filled with cerebrospinal fluid) due to the excess accumulation of cerebrospinal fluid (the colorless body fluid found circulating in and around brain and spinal cord).
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Micromelia: Severely shortened and imperfectly developed extremities.
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Enlarged Fontanelles: Enlarged frontal bones.
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Pronounced Midface: The affected child had a noticeable midfacial region.
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Pulmonary Hypoplasia: A condition characterized by improper development of lungs during birth.
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Mild Hydrocephalus: Build-up of fluid in the cavities of the brain.
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Excess fluid buildup in the skin, around the heart, and the baby's lungs.
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Shorter neck.
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Protuberant abdomen.
What Are the Radiological Features of Baby Rattle Pelvic Dysplasia?
The radiographic features of this condition mentioned below are based on the case report.
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The density of the bone present in the skull was normal.
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There is a lack of ossification in the cervical, thoracic, and lumbar vertebrae regions.
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Complete lack of ossification in pedicles and spinous process (a bony process that projects posteriorly from the vertebral body) in the regions of sacral vertebrae.
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Bell-shaped chest region with a fractured and wavy ribcage.
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Elongated collarbone.
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The widening was noted in the metaphyseal (neck portion) regions of the limbs' long bones.
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Shorter diaphyseal regions (central portion) with thick cortex.
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Bifid distal ends of the long bones (bifid humerus).
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Shorter digits were noted with the abnormal shape of the tarsal bones (cluster of short seven bones).
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Baby rattle appearance: Abnormally tall and broad ilium bone (the most significant part of the hipbone). The acetabular roof, the main weight-bearing area of the hip joint, was seen to be underdeveloped. And there was the complete absence of the greater sciatic notch (indentation of the ilium bone). This abnormality in the hip bone gave rise to the appearance of baby rattle-like morphology.
What Are the Histomorphologic Features of Baby Rattle Pelvic Dysplasia?
The histomorphologic features of chondro-osseous morphology were shown to be abnormal and unique in the cases of Baby rattle pelvic dysplasia.
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The thighbone and ribcage morphologic features showed regions of normal-appearing cartilage along with mesenchymal areas (undifferentiated cells). The areas of cartilage showed acellular region with irregular cellular distribution.
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Areas adjacent to the cartilaginous area showed enormous, irregular collections of undifferentiated mesenchymal cells with prominent blood vessels.
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Whereas the cartilaginous area showed no evidence of blood vessels.
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There is a lack of endochondral ossification (an essential process of bone formation when the cartilage is replaced with bone).
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Evidence of abnormal ossification of mesenchymal areas is seen. This, in turn, results in hypercellular bone formation.
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A zone of undifferentiated mesenchymal cells was noted between the cartilage and the hypercellular bone formed by endochondral ossification.
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Resorption of mesenchymal bone cells by the osteoclasts was noted.
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Histomorphologic features of metaphyseal bones showed poor organization of collagen with irregular calcification.
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These unique chondro-osseous morphology features of Baby rattle pelvic dysplasia distinguished them from Achondrogenesis.
How Is Baby Rattle Pelvic Dysplasia Treated?
As of now, there is no cure for Baby rattle pelvic dysplasia. Babies with this condition are stillborn or die shortly after birth. Valérie Cormier-Daire et al. reported that the pregnancy was ceased by Pitocin-induced vaginal delivery (injection of a hormone called oxytocin to promote uterine contraction).
Conclusion:
Baby rattle pelvic dysplasia is a lethal skeletal disorder with unique radiologic and histomorphologic features. The clinical manifestations of this condition are shown to be very similar to the condition called achondrogenesis. Achondrogenesis is a rare skeletal condition characterized by developmental defects of the bone and the cartilage of the developing baby. One of the life-threatening symptoms seen in both conditions is pulmonary hypoplasia which puts the baby's life in danger. The prognosis of this condition is very low. Still, more research and studies on other Baby rattle pelvic dysplasia case reports are needed to get better knowledge on this condition and its mode of inheritance.
