What is an abnormal rib cage at birth called?

Abnormal Rib Cage at Birth: Terminology and Clinical Context

The specific terminology for an abnormal rib cage at birth depends on the underlying condition, but common terms include "thoracic dystrophy," "narrow thorax," "small thoracic cage," or specific syndrome names like "asphyxiating thoracic dystrophy" (Jeune syndrome).

Specific Terminology Based on Clinical Presentation

Rachitic Changes

• "Rachitic rosary" refers to prominent knobs of bone at the costochondral joints in patients with rickets, also known as beading of the ribs, creating the appearance of large beads under the skin of the rib cage 1.
• "Harrison's groove" is a horizontal groove along the lower border of the thorax corresponding to the costal insertion of the diaphragm, appearing in rickets due to defective mineralization where the diaphragm pulls the softened bone inward 1.

Skeletal Dysplasias

• "Abnormal chest or ribs" is the general descriptive term used when skeletal dysplasias are detected prenatally, often accompanied by shortened or bowed limbs and undermineralized skull 1.
• "Short rib syndrome" or "short rib-polydactyly syndrome" describes conditions with very short ribs and narrow thorax, often fatal due to respiratory compromise 2, 3.
• "Asphyxiating thoracic dystrophy" (Jeune syndrome) presents with a small and narrow thoracic cage with short broad ribs and abnormal costal cartilages 4.

Normal Developmental Anatomy at Birth

Physiological Rib Cage Configuration

• At birth, the ribs extend almost at right angles from the vertebral column, making the rib cage more circular than in adults and lacking mechanical efficiency 1.
• The ribs are already elevated at birth, which is why rib cage motion contributes little to tidal volume in infants 1.
• Progressive mineralization of the ribs occurs concurrently with the infant assuming upright posture, with rib cage contribution to breathing reaching adult-like values between 1 and 2 years of age 1.

Pathological Conditions

Congenital Rib Anomalies

• Congenital rib anomalies occur most commonly on the concavity of thoracic or thoracolumbar congenital scoliosis, particularly with unilateral failure of vertebral segmentation 5.
• These anomalies are classified as simple or complex and occur in approximately 19% of patients with congenital spinal deformities 5.

Clinical Significance in Skeletal Dysplasias

• The rib cage perimeter to thoracic circumference ratio can be abnormal in fetuses with skeletal dysplasias, particularly decreased in short rib-polydactyly syndrome 2.
• Detection typically occurs at 18-20 weeks of gestation during routine fetal anomaly screening, though earlier detection with distinctive skeletal features suggests more severe phenotypes 1.

Important Clinical Caveats

• The term used should reflect the specific underlying pathology rather than just describing the appearance, as this guides prognosis and management 1.
• Respiratory compromise is the primary concern with thoracic cage abnormalities at birth, as chest expansion impairment can lead to alveolar hypoventilation and respiratory failure 4.
• Genetic testing and expert consultation are essential when skeletal dysplasia is suspected, as interpretation requires correlation with clinical findings 1.