What causes the finger in glove (gloved finger) sign in the lungs on chest radiography or CT?
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Answer:
Mucoid impaction in dilated bronchi causes the finger in glove sign: branching, tubular, finger-like opacities radiating from the hilum on chest radiography or CT [1]. The sign localises the mucus, not the cause. On non-contrast CT, mucus that looks denser than the paraspinal muscles is pathognomonic of allergic bronchopulmonary aspergillosis [3].
Why is it called so?
The impacted bronchi branch outwards from the hilum like the splayed fingers of a surgical glove, the hilum standing in for the hand [1].
Pathophysiology
Mucus accumulates inside a bronchus whose lumen is already widened, either congenitally or because chronic inflammation and obstruction have dilated it. Because the mucus distends the airway rather than coating it, the opacity takes the calibre of that bronchus and follows its branching, which is why it points back to the hilum. Clearance then fails in the plugged segment and inflammation perpetuates the dilatation, so the opacity persists rather than clearing [1]. In congenital bronchial atresia the segment beyond the plug stays hyperinflated instead of collapsing [7].
Alternative names: Finger-in-glove sign, gloved finger sign, toothpaste shadow, bronchocele (for the mucus-filled bronchus itself)
Other associated named signs: Signet ring sign (dilated bronchus beside its artery), tram-track sign (bronchiectasis in the horizontal plane), air bronchogram (the aerated, not impacted, bronchus)
What does the attenuation of the mucus tell you?
This is the observation that changes the report. On non-contrast CT, mucus that looks visually denser than the paraspinal muscles is high-attenuation mucus (HAM), and the 2024 ISHAM working group classes it as pathognomonic of allergic bronchopulmonary aspergillosis (ABPA): sensitivity is only 35 percent, but specificity is 100 percent, and its presence confirms ABPA even when the remaining criteria are not met [3]. Among 155 patients with ABPA, 29 (18.7 percent) had HAM, and on multivariate analysis it independently predicted relapse (odds ratio 3.61, 95 percent CI 1.23 to 10.61) without influencing whether complete remission was achieved [2]. If you would rather measure than compare, a threshold of 70 HU or more agrees substantially with the paraspinal muscle comparison (kappa 0.72) [4].
What causes a finger in glove opacity?
Distribution, mucus attenuation and the patient decide between these; the sign itself does not.
| Cause | Typical distribution | What separates it |
|---|---|---|
| Allergic bronchopulmonary aspergillosis | Central and upper-lobe, often bilateral, with bronchiectasis proximal to the plugs | High-attenuation mucus, underlying asthma or cystic fibrosis, total IgE 500 IU/mL or more [2,3] |
| Congenital bronchial atresia | One segment, usually an upper lobe | Mucus-filled bronchocele with a hyperinflated segment beyond it, in an asymptomatic patient [7] |
| Obstructing endobronchial lesion (bronchogenic carcinoma, carcinoid, hamartoma, metastasis) | One segment or lobe, distal to the lesion | A visible endobronchial mass or bronchial cut-off. This is the referral for bronchoscopy [1] |
| Cystic fibrosis | Diffuse, upper-lobe predominant | Known diagnosis with widespread bronchiectasis. ABPA complicates 8.9 percent (95 percent CI 7.4 to 10.7) of cystic fibrosis [6] |
| Broncholithiasis or foreign body aspiration | One segment, often dependent | Calcified peribronchial node or aspirated material sitting at the cut-off [1] |
Current ABPA criteria and classification
ABPA is the diagnosis worth confirming or excluding, and its criteria were revised in 2024 [3].
| Component | Requirement |
|---|---|
| Predisposing condition | Asthma, cystic fibrosis, chronic obstructive lung disease or bronchiectasis, or else a compatible clinico-radiological presentation. The second option is new in 2024 and lets ABPA be diagnosed without a predisposing disease |
| Essential, both required | Aspergillus fumigatus specific IgE 0.35 kUA/L or more, and serum total IgE 500 IU/mL or more |
| Other components, any two | Positive IgG against A. fumigatus; blood eosinophils 500 cells per microlitre or more, historical counts accepted; thin-section CT consistent with ABPA (bronchiectasis, mucus plugging, high-attenuation mucus) or fleeting opacities on the chest radiograph |
The same revision expanded the radiologic classification from four classes to five, adding mucus plugging that is not hyperattenuating [3].
| Class | Imaging |
|---|---|
| ABPA-S (serologic) | No bronchiectasis and no mucus plugging |
| ABPA-B | Bronchiectasis without mucus plugging |
| ABPA-MP, new in 2024 | Mucus plugging that is not hyperattenuating, with or without bronchiectasis |
| ABPA-HAM | High-attenuation mucus. Retained as an independent, pathognomonic class |
| ABPA-CPF | Two or more of fibrosis, fibro-cavitary lesions, fungal ball, pleural thickening |
What to do when you see it
- Name the segment, and compare the mucus against the paraspinal muscles. That one comparison can confirm ABPA by itself [3].
- Trace the opacity back to the hilum and look for a bronchial cut-off or an endobronchial mass [1].
- If the segment beyond the plug is hyperinflated in a well patient, consider congenital bronchial atresia rather than biopsy [7].
- Suggest total IgE and Aspergillus fumigatus specific IgE. ABPA was found in 12.9 percent (95 percent CI 7.9 to 18.9) of patients attending specialist asthma clinics [5].
- Do not report plugging as incidental. Among 4363 patients with chronic obstructive pulmonary disease followed for a median 9.5 years, mortality was 34.0, 46.7 and 54.1 percent with mucus plugs in 0, 1 to 2, and 3 or more segments (adjusted hazard ratio 1.24, 95 percent CI 1.10 to 1.41 for 3 or more) [8]. In asthma, plugs in 4 or more segments occurred in 67 percent of patients with an FEV1 below 60 percent predicted, against 6 percent of those above 80 percent [9].
Frequently asked questions
What does the finger in glove sign mean?
It means mucus is impacted inside dilated bronchi, producing branching tubular opacities that radiate from the hilum and take the calibre of the airways they fill [1]. It is a statement about the airway, not about a disease, and the cause is decided by the distribution of the plugs and the attenuation of the mucus.
Is the finger in glove sign always ABPA?
No. ABPA is the commonest cause in a patient with asthma, but a solitary finger in glove in an adult without asthma should be treated as an obstructing endobronchial lesion until bronchoscopy says otherwise [1].
What is high-attenuation mucus?
High-attenuation mucus is mucus that appears visually denser than the paraspinal muscles on non-contrast CT, or measures 70 HU or more [3,4]. The 2024 ISHAM working group treats it as pathognomonic of ABPA, with 35 percent sensitivity and 100 percent specificity, so it confirms the diagnosis even if the serologic criteria are not met [3].
Can you see the finger in glove sign on a chest X-ray?
Yes. It was described on the chest radiograph as branching tubular opacities radiating from the hilum, and that remains the classic appearance [1]. CT adds what the radiograph cannot: the calibre and branching of the individual plugged bronchi, the state of the airway beyond them, and the attenuation of the mucus, which is the feature that separates ABPA from every other cause [1,3].
References
- Martinez S, Heyneman LE, McAdams HP, Rossi SE, Restrepo CS, Eraso A. Mucoid impactions: finger-in-glove sign and other CT and radiographic features. Radiographics. 2008;28(5):1369-1382.
- Agarwal R, Gupta D, Aggarwal AN, Saxena AK, Chakrabarti A, Jindal SK. Clinical significance of hyperattenuating mucoid impaction in allergic bronchopulmonary aspergillosis: an analysis of 155 patients. Chest. 2007;132(4):1183-1190.
- Agarwal R, Sehgal IS, Muthu V, Denning DW, Chakrabarti A, Soundappan K, et al. Revised ISHAM-ABPA working group clinical practice guidelines for diagnosing, classifying and treating allergic bronchopulmonary aspergillosis/mycoses. Eur Respir J. 2024;63(4).
- Hattori S, Oguma T, Ishiguro T, Suzuki J, Fukunaga K, Shimoda T, et al. High attenuation mucus in bronchi with allergic bronchopulmonary mycosis. Mycoses. 2024;67(2):e13705.
- Agarwal R, Aggarwal AN, Gupta D, Jindal SK. Aspergillus hypersensitivity and allergic bronchopulmonary aspergillosis in patients with bronchial asthma: systematic review and meta-analysis. Int J Tuberc Lung Dis. 2009;13(8):936-944.
- Maturu VN, Agarwal R. Prevalence of Aspergillus sensitization and allergic bronchopulmonary aspergillosis in cystic fibrosis: systematic review and meta-analysis. Clin Exp Allergy. 2015;45(12):1765-1778.
- Jederlinic PJ, Sicilian LS, Baigelman W, Gaensler EA. Congenital bronchial atresia. A report of 4 cases and a review of the literature. Medicine (Baltimore). 1987;66(1):73-83.
- Diaz AA, Orejas JL, Grumley S, Nath HP, Wang W, Dolliver WR, et al. Airway-occluding mucus plugs and mortality in patients with chronic obstructive pulmonary disease. JAMA. 2023;329(21):1832-1839.
- Dunican EM, Elicker BM, Gierada DS, Nagle SK, Schiebler ML, Newell JD, et al. Mucus plugs in patients with asthma linked to eosinophilia and airflow obstruction. J Clin Invest. 2018;128(3):997-1009.
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