Smoking-Associated Endotracheal Hair Growth: A Case Report on Tracheal Complications

Introduction

The tracheal surface is naturally coated with respiratory epithelium, containing columnar ciliated epithelial cells. Exposure to cigarette smoke increases the odds of epithelial alterations, such as squamous epithelial metaplasia [1]. While hair growth is not typically recognized as such an alteration, it has been explored in an animal model of tracheal reconstruction with auricular cartilage, in which hair growth and skin desquamation occurred 3 months after surgery, leading to secondary obliteration of the airway [2]. In human medicine, there is only one similar case reported, in which, after the patient coughed out a hair, with a latency of 12 to 16 years after restoration of a tracheotomy using a cutaneous transplant, endoscopic cryotherapy was performed, but hair-growth recurred 18 years later [3]. Another case of hair in the respiratory system concerns the bronchus but has a different etiology, in which a 27-year-old non-smoking patient had hemoptysis with hair in the sputum but no other accompanying symptoms. Further work-up revealed a mediastinal cystic teratoma with bronchial communication [4].

We present a case of successful endoscopic treatment of intratracheal hair growth in a smoking patient who previously received an autologous skin and cartilage graft from the ear for reconstruction of a tracheal defect caused by long-term tracheostomy.

Case Report

PATIENT INFORMATION:

The patient was a 52-year-old man with a body mass index of 30.2 kg/m². The first clinical presentation was at the age of 35 years. Primary symptoms were respiratory distress attacks at night, snoring, hoarseness, and chronic coughing, where once, he coughed out a hair 5 cm in length. The patient was smoking from the age of 20 to 50 years, with a cumulation of 31 pack years. The case history began at the age of 10 years with a near-drowning accident in the sea, which was followed by first aid maneuvers that accidently damaged the larynx. A tracheotomy was indicated, and a tracheostoma was established, which remained in place for a total of 3.5 years. Five days after closure, a re-tracheotomy was indicated, as a bacterial infection of the proximal trachea caused necrotizing tissue damage. Thus, the area was surgically reconstructed using an auricular cartilage and skin auto-transplantation.

Upon physical examination, the patient presented with an anteromedial scar from the tracheotomy, distal of the larynx, an externally visible tracheal structural deviation, and a hoarse voice. Imaging by computed tomography showed tracheal constriction and loss of wall thickness (Figure 1). Lung function testing indicated a combined obstructive and restrictive flow pattern, with a distinctly flattened inspiratory flow-volume curve, suggesting an extrathoracic stenosis. Additionally, there was pronounced hypoventilation at physical strain in cardio-pulmonary exercise testing, and an otherwise asymptomatic increase of C-reactive protein (3.2 mg/dL) and leucocyte count (13.4 G/L). Flexible bronchoscopy was challenging due to altered tracheal anatomy and revealed a 5-cm-long sub-laryngeal necrotizing ulcer. Additionally, there were signs of acute tracheal inflammation, formation of fibrinous plaques, and scab areas. Surprisingly, hair was growing in the graft area. Histological examination confirmed a lymphocytic tracheitis, with reactive-regenerative keratinized squamous epithelium and hair follicular units with mycotic and bacterial vegetations of Corynebacteria and Klebsiella oxytoca. Bronchoscopy images are provided in Figure 2.

Consequently, combined local bronchoscopic and systemic antimicrobial and anti-inflammatory treatment was established. Bronchoscopic therapy included endoscopic hair plucking by forceps, in which the larynx and trachea were supportively aligned manually from the outside. Permeability of the airway was restored by removing fibrin plaques and scab debris. Pharmacological therapy consisted of anti-inflammatory, empirical antimycotic, and antibiotic treatment with a prednisolone taper starting at 12.5 mg, 200 mg fluconazole, and 1g amoxicillin/clavulanic acid twice daily for 2 months, respectively.

Subsequent reassessment after 5 weeks showed significant improvement. In bronchoscopic re-inspection after 10 weeks, the trachea had recovered across the whole circumference, without residual signs of inflammation; pharmacologic therapy was therefore terminated. However, hair growth in the graft area persisted. In several follow-up bronchoscopy sessions, in about yearly intervals, triggered by the patient’s experience of tracheal irritation, 6 to 9 endotracheal hairs with a length up to 5 cm were repeatedly removed. Hair grew in a proximal direction, occasionally exceeding the vocal cords, reaching the oral cavity. In recent years, the proximal trachea was increasingly coated with fibrinous plaques and scab debris, and the bronchial system was obstructed with mucus, which was bronchoscopically resolved. Endoscopic cryoablation performed consequently could contain hair growth to a higher degree. Finally, an endoscopic argon plasma coagulation was performed, as the patient was 49 years old. In the following reassessment 1 year after coagulation, only 2 hairs had to be removed. A further coagulation of the graft area neutralized all hair follicles permanently up till then. In the latest follow-up 2 years after re-coagulation, the trachea appeared hairless but still showed structural damage and scars, with a new small superficial remnant scar of laser coagulation. Moreover, there was less scab debris, fibrin plaques, and obstructive mucus.

The repeated endoscopic treatment sessions were tolerated well by the patient, who experienced them as highly relieving. Spirometry results, as compared with the initial evaluations, also improved, especially concerning obstruction. Of interest, marked symptomatic and functional improvement was especially achieved after the patient’s smoking cessation. The case timeline is displayed in Figure 3.

Discussion

To the best of our knowledge, this is one of very few case reports of endotracheal hair growth specifically associated with auricular cartilage and cutaneous auto-transplantation. This case is unique in many aspects and could provide a possible therapeutic approach to similar cases. What we want to highlight is a possible association of smoking habits and the specific symptoms, which might be a potential underlying pathomechanism.

Several molecular pathways are simultaneously involved in hair follicle stimulation and hair growth, and some of these have also been shown to be locally induced in the respiratory epithelium as a response to chronic smoke exposure. Hair follicle stem cells are epithelial stem cells located in in the follicular bulge and have the potential to differentiate in various epithelial cell types [5]. In addition, reports suggest an increased accumulation of hair papilla cells in damaged or incised auricular cartilage [6]. Follicle morphogenesis comprises induction, organogenesis, and cytodifferentiation. An interplay of various molecular signal pathways mediates this process. The sonic hedgehog (Shh) and wingless/integrated (WNT)/β-catenin pathways are crucial for hair proliferation, development, and cycling and can induce epithelial metaplasia [7]. In detail, Shh onsets the growth and maturation of the dermal papilla, induces the hair anagen proliferation phase, mediates the differentiation of precursor cells, and is essential in the development in various functional follicle components [8]. Similarly, the WNT/ β-catenin pathway is pivotal in hair growth for stem cell activation, follicle differentiation, and anagen stabilization and is linked with tumor formation [8]. The epidermal growth factor is important in hair regrowth by stimulating the WNT/β-catenin pathway and activating the hair follicle [9]. In long-term smoke exposure, Shh and WNT pathways are activated in bronchial epithelial cells [10]. Additionally, WNT and β-catenin pathways are upregulated in smokers, correlate with the reduction of forced expiratory volume in the first second [11], and there is an enhanced activation of the epidermal growth factor receptor [12]. A constellation of all described mechanisms is shown in Figure 4. These findings may support our hypothesis that the smoking habits in the presented case may have induced and stimulated endotracheal hair growth. Of course, this assumption cannot be proven due to the rarity of such cases, but we assume that, in such cases, smoking cessation as a part of the therapeutic approach is certainly relevant. Of note, in the patient presented in this case, extra and intrathoracic airflow also improved significantly after the patient had stopped smoking.

Conclusions

Endotracheal hair growth is a rare complication of autologous tracheal cartilage and skin graft transplantation. This is the second case report referring to a similar condition and therapy strategy. In such cases, we recommend the targeted use of argon-plasma coagulation and anti-inflammatory and anti-microbial treatment, when indicated by bronchoscopic inspection, imaging, and laboratory parameters. Cigarette smoke has the ability to alter signaling pathways in respiratory epithelial cells that are simultaneously related to hair follicle proliferation. Therefore, smoking cessation is likely pivotal in such cases of patients receiving skin/cartilage grafts into the respiratory system.