PIEZO2 Compound Heterozygous Mutations Inducing Tracheobronchomalacia: A Case Study and Mechanistic Exploration
Tracheobronchomalacia (TBM) is a congenital or acquired disorder characterized by abnormal cartilage development in the trachea and bronchi, leading to excessive airway collapse during exhalation. Defined by a cross-sectional reduction of ≥50%, TBM severity is categorized as mild (50%–75% reduction), moderate (75%–90%), or severe (>90%). Etiologies range from primary genetic defects to secondary factors such as infections, cardiovascular anomalies, or connective tissue disorders. This case study highlights a rare neonatal presentation of severe TBM linked to compound heterozygous mutations in the PIEZO2 gene, elucidating the molecular mechanisms underlying cartilage maldevelopment and clinical management challenges.
Case Presentation
A 20-day-old female neonate, born preterm at 36 weeks and 6 days gestation, was admitted to the neonatal intensive care unit (NICU) with dyspnea, cyanosis, and oxygen saturation of 85%. Initial assessments revealed a history of neonatal pneumonia and sepsis, alongside physical findings of bilateral coarse breath sounds, talipes equinovarus (clubfoot), reduced muscle tone, and diminished primitive reflexes. Cardiac and abdominal examinations were unremarkable.
Imaging studies provided critical insights:
- Computed tomography (CT) identified fractures in the 6th–10th left ribs, interstitial lung changes, and pleural thickening.
- Magnetic resonance imaging (MRI) detected ischemic lesions in periventricular white matter.
- Echocardiography ruled out vascular anomalies compressing airways.
Bronchoscopy revealed dynamic airway collapse: the epiglottis curled during inspiration, while the trachea and left bronchus showed >50% obstruction during expiration (Figure 1A–C). Additionally, the basal segment of the right lower lobe bronchus exhibited partial obstruction. These findings confirmed severe TBM, prompting genetic investigation.
Genetic Analysis
Whole-exome sequencing (WES) using the Illumina NovaSeq 6000 platform identified two pathogenic PIEZO2 mutations:
- c.6049C>G (paternally inherited), predicted to damage protein function (Mutation Taster score: 0.944).
- c.3754C>T (maternally inherited), classified as disease-causing (Mutation Taster score: 1.0).
These compound heterozygous variants disrupt the PIEZO2 mechanosensitive ion channel, essential for chondrocyte responses to mechanical stress. The loss-of-function mutations impair calcium influx, critical for cartilage maturation and structural integrity, aligning with the patient’s tracheobronchial instability.
Pathophysiological Mechanisms
PIEZO2, a mechanosensitive cation channel, regulates chondrocyte proliferation, differentiation, and extracellular matrix homeostasis by transducing mechanical stimuli into electrochemical signals. In healthy cartilage, mechanical loading activates PIEZO2, triggering calcium-dependent pathways that sustain tissue strength. Mutations compromising this pathway lead to defective cartilage remodeling, as seen in this case.
The identified variants (c.6049C>G and c.3754C>T) likely disrupt channel gating or pore formation, rendering chondrocytes unresponsive to physiological strain. This mechanoinsensitivity results in inadequate tracheobronchial support, predisposing to dynamic collapse during respiration. The rib fractures and ischemic brain lesions observed may also reflect systemic connective tissue vulnerability due to impaired mechanotransduction.
Clinical Management and Follow-Up
At seven months, tracheostomy was performed to bypass the malacic airway segments, significantly alleviating respiratory distress. Postoperative care included biannual hospitalizations for antibiotic therapy targeting recurrent pulmonary infections, evidenced by persistent consolidations on follow-up CT scans (Figure 1D–F). Despite these challenges, the patient exhibited catch-up growth in physical and motor development, underscoring the reversibility of developmental delays with targeted interventions.
Discussion
This case illustrates the expanding role of genetic testing in diagnosing TBM, particularly when structural anomalies coexist with syndromic features. While acquired TBM often resolves with growth, congenital forms associated with genetic mutations necessitate lifelong management. The compound PIEZO2 mutations here represent a novel etiology, broadening the genetic spectrum of connective tissue disorders.
PIEZO2’s role in cartilage biology is underscored by its expression in developing tracheobronchial rings, where it mediates chondrocyte adaptation to mechanical forces. Murine models show that Piezo2 knockout impairs tracheal cartilage formation, corroborating this patient’s phenotype. Furthermore, PIEZO2 variants are linked to arthrogryposis and proprioceptive deficits, suggesting pleiotropic effects beyond the airways.
Clinically, early tracheostomy in severe TBM mitigates hypoxic insults and facilitates developmental progress. However, recurrent infections in this patient highlight the need for vigilant surveillance, as malacic airways compromise mucociliary clearance, predisposing to pneumonia.
Conclusion
This report establishes PIEZO2 mutations as a causative factor in congenital TBM, emphasizing the importance of genetic screening in unexplained airway malformations. Mechanistically, PIEZO2 dysfunction disrupts chondrocyte mechanotransduction, leading to tracheobronchial instability. Multidisciplinary management—integrating surgery, infection control, and developmental support—is critical for optimizing outcomes. Future studies should explore therapeutic strategies to modulate PIEZO2 activity, potentially mitigating cartilage defects in affected individuals.
doi.org/10.1097/CM9.0000000000001500
Was this helpful?
0 / 0