Abstract
A 25-year-old man, who was taking treatment for his poorly controlled asthma, presented with symptoms of cough with expectoration, gradually progressive shortness of breath, fever on and off and diffuse wheeze for 2 years. Chest X-ray revealed hyperinflation of lung field with dense opacification at right upper lobe. High-resolution CT chest showed bilateral patchy consolidation, central bronchiectasis and high-attenuation mucus (HAM) impaction. His blood absolute eosinophil count, total serum IgE level, Aspergillus fumigatus specific IgE and IgG level were 1910, 16760 kU/L, 59.8 kU/L and 147.41 kU/L, respectively. Diagnosis of allergic broncho pulmonary aspergillosis (ABPA) was established according to International Society for Human and Animal Mycology society guidelines. He was started on systemic steroids and doing well after 6 months of follow-up. Our case illustrates HAM, which is a rare but typical radiological feature of ABPA.
Keywords: respiratory medicine, asthma, immunology
Background
Allergic broncho pulmonary aspergillosis (ABPA) is an airway hypersensitivity disorder to the fungus Aspergillus fumigatus and related species. It leads to chronic airway inflammation and damage. Prevalence of ABPA among patients with asthma and cystic fibrosis is approximately 1%–2% and 2%–15%, respectively.1 Patients present with exacerbations of asthma, productive cough with brownish-black mucus expectoration, haemoptysis, fever, malaise and weight loss.1 The characteristic radiological finding in ABPA is high-attenuation mucus (HAM).
Case Presentation
A 25-year-old man presented with symptoms of cough with expectoration, gradually progressive shortness of breath and fever on and off for 2 years. He lost 6 kg weight over the last 2 years. He was taking treatment for asthma (formoterol and budesonide combination inhaler) for last 3 years but had four episodes of exacerbation in between, for which he had to be admitted in the hospital. He had no history of chills, recent travel, haemoptysis and cigarette smoking. He had normal bowel function, no history of abdominal pain, no history of any major illness other than asthma in the past. He was started on antitubercular treatment on radiological basis twice despite negative sputum acid fast bacillus and nucleic acid amplification test without any improvement. On presentation at our hospital, his heart rate and blood pressure were of 84/min and 130/70, respectively. He had mildly increased respiratory rate of 18/min but saturation (sP02) at room air was 98%. On physical examination, he had diffuse wheeze all over the chest. Other systemic examinations were normal.
Investigations
Chest X-ray revealed hyperinflation of lung field with dense opacification at right upper lobe and some nodular opacification over left lung (figure 1). High-resolution CT (HRCT) chest showed bilateral patchy consolidation, central bronchiectasis and mucus impaction. Along with low attenuated mucus impaction, there were areas of highly attenuated mucus, which was visually denser than the paraspinal skeletal muscle (figures 2 and 3). He was hence investigated for ABPA. Absolute eosinophil count was 1910. Total serum IgE was 16 760 kU/L. A. fumigatus specific IgE and IgG level were 59.8 kU/L and 147.41 kU/L, respectively. Diagnosis of ABPA was established according to International Society for Human and Animal Mycology society guidelines.2
Figure 1.
Chest X-ray revealed hyperinflation with dense opacification at right upper lobe (arrow) and some nodular opacification over left lung.
Figure 2.
High-resolution CT chest showing small area of high-attenuation mucus on right side.
Figure 3.
High-resolution CT chest at a lower level showing extensive bilateral patchy consolidation and mucus impaction. Along with low attenuated mucus impaction, there were areas of highly attenuated mucus (pointed with red arrow) which was visually denser than the paraspinal skeletal muscle.
Treatment
Oral prednisolone at a dose of 0.5 mg/kg was started. Formoterol and budesonide combination inhaler was continued.
Outcome and follow-up
He is currently doing well after 6 months of follow-up.
Discussion
HRCT is the investigation of choice to show bronchiectasis and HAM in ABPA. Bronchial mucous plugging is frequently seen in HRCT, which is usually low attenuation or hypodense. Rarely bronchial mucous plugging may be high-attenuated on CT. HAM impaction is considered to be present if density of mucus plugs is more than that of paraspinal skeletal muscles. Goyal et al first proposed HAM as a distinct finding in ABPA in 1992.3
The exact etiopathogenesis of HAM impaction is unclear. It is probably due to desiccated mucus or the presence of calcium and metals like iron and manganese in the mucus.4 Differential diagnosis of HAM can be aspiration of radiopaque material or alveolar haemmorhage.5
In one study of 155 patients of ABPA, 29 patients (18.7%) were identified to have HAM impaction. In this study HAM was associated with initial serological severity and frequent relapses but it did not influence complete remission.4 In another study out of 100 patients of ABPA, 47 patients had mucus impaction and 28 of them had HAM.6 In this study when compared with non-HAM category, HAM category patients showed higher values of all the serological tests.
So, significance of HAM is multipronged. (i) It is an interesting radiological finding which clinches the diagnosis in proper clinical setting. (ii) It has prognostic relevance in ABPA both in terms of serological association and frequency of relapse.
Exact reason why HAM is associated with poorer outcome is not known. Proposed reasons are: (i) the mucus in HAM is more impacted and more inspissated; (ii) ABPA with HAM may represent a subgroup of patients of ABPA, who have more severe inflammation, which may also have some genetic basis.4
Current treatment of ABPA is systemic steroid. Antifungal triazoles are second line therapy.7
Learning points.
In proper clinical setting, presence of high-attenuation mucus (HAM) points towards diagnosis of allergic broncho pulmonary aspergillosis (ABPA).
It is associated with poor prognosis.
HAM is associated with serological severity in ABPA.
Presence of HAM is associated with frequent relapse.
Acknowledgments
We thank patient for inclusion in the study.
Footnotes
Twitter: @DrSoumitraGhos1
Contributors: RB, SG, ST: drafting the article, analysis and interpretation and revising its intellectual content. NH: drafting the article and manuscript preparation.
Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests: None declared.
Provenance and peer review: Not commissioned; externally peer reviewed.
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