Feather duvet lung

Abstract

A 43-year-old non-smoker was referred with a 3-month history of malaise, fatigue and breathlessness. Blood avian precipitins were strongly positive. Lung function testing confirmed a restrictive pattern with impaired gas transfer. A ‘ground glass’ mosaic pattern was seen on CT imaging, suggestive of hypersensitivity pneumonitis. Although he had no pet birds, on closer questioning he had recently acquired a duvet and pillows containing feathers. His symptoms, chest radiograph and lung function tests improved after removal of all feather bedding, and he was also started on oral corticosteroid therapy. Our case reinforces the importance of taking a meticulous exposure history and asking about domestic bedding in patients with unexplained breathlessness. Prompt recognition and cessation of antigen exposure may prevent the development of irreversible lung fibrosis.

Background

Feather duvet lung (FDL), is an immunologically mediated form of hypersensitivity pneumonitis (HP), also sometimes called extrinsic allergic alveolitis. FDL is caused by inhalation of organic dust from duck or goose feathers found in duvets and pillows. Antigen inhalation triggers an immunological cascade, resulting in lung parenchymal inflammation. Repeated exposure may result in irreversible lung fibrosis. Healthcare professionals are typically taught to ask patients with respiratory symptoms whether they have pets at home, such as birds, but in the authors’ experience, history taking does not usually extend to asking about feather exposure in duvets and pillows. This is an important omission since the use of feather, rather than synthetic, bedding is common. During the last half century, feathers stuffed linens have increased massively in popularity in the UK. In the first 4 months of 2015, 7.6 million duvets were sold in the UK according to market research institute Growth from Knowledge.¹

Symptoms are non-specific, ranging from systemic malaise and influenza like symptoms, through to acute breathlessness (4–8 hours following feather antigen exposure).² It is therefore entirely probable that cases of FDL are missed, or at best, diagnosed late.

Case presentation

In November 2016, a 43-year-old man presented to his general practitioner (GP) with a 3-month history of malaise, fatigue and breathlessness. These symptoms were initially attributed to a lower respiratory tract infection. He had no other respiratory symptoms. His symptoms improved initially, but later that month recurred, such that he had to take 14 days off work. He was a non-smoker, and normally well, apart from occasional sciatica and tinnitus. His GP arranged initial blood tests which were all normal (full blood count, renal function, liver function and C reactive protein).

In December 2016, he described worsening breathlessness. A chest radiograph (CXR) was reported as ‘normal’ (figure 1). By now he was describing breathlessness walking between rooms at home. His GP referred him for an urgent respiratory clinic review and also phoned for advice. During the phone discussion, one of the authors (OJD) reviewed the patient’s CXR and disagreed with the original report. OJD phoned the patient for more clinical information and noted that the patient sounded alarmingly tachypnoeic on answering the phone. His history was reviewed and the patient described living in a warm dry house with his wife. They had a loft which he rarely entered. They had an en-suite bathroom, and despite an extractor fan, he described a small amount of mould above the shower and window. They had a cat and a dog, but no birds. They had recently acquired a feather duvet and feather pillows, having formerly had synthetic bedding. His hobbies included playing music as part of a band (guitar, saxophone) and his work was office-based with no obvious occupational exposures. His symptoms did not improve when on holiday. He had no relevant foreign travel history or drug history, apart from occasional paracetamol use.

Figure 1.

Chest radiograph reported as ‘normal’ noting diffuse ground glass shadowing in all zones.

Investigations

Blood tests

The following blood tests were normal/negative (full blood count including eosinophils, full biochemistry screen, C reactive protein, immunoglobulins, HIV, autoantibodies, total IgE, antineutrophil cytoplasmic antibody, rheumatoid factor, micropolyspora faeni IgG, A spergillus IgG/IgE).

Avian precipitins were highly abnormal (budgie 80.6 mg/L, pigeon 46.3 mg/L and parrot 67.8 mg/L), normal defined in our lab as <25 mg/L.

Imaging

Our patient’s CXR report (figure 1) was initially reported as normal (although we disagreed).

He subsequently had a CT pulmonary angiogram with high-resolution reconstruction (to exclude pulmonary thromboembolic as well as interstitial lung disease) (figures 2–4), reported as showing a ground glass, mosaic pattern in both lungs, with borderline enlarged hilar nodes, presumed reactive. No pulmonary emboli were seen. The radiologist suggested possible HP.

Figure 2.

CT scan showing mosaic pattern apical axial view.

Figure 3.

CT scan showing mosaic pattern middle zones axial view.

Figure 4.

CT scan mediastinal axial slice with prominent reactive borderline enlarged mediastinal and hilar nodes.

Pulmonary function tests

His initial clinic spirometry (visit 1) was restrictive in pattern, with a forced expiratory volume within 1 s (FEV₁) of 71% and forced vital capacity (FVC) of 64% predicted (figure 5). Gas transfer was impaired (visit 2), diffusion capacity for carbon monoxide (DL_CO) 48% and transfer coefficient for carbon monoxide (K_CO) 65% predicted. Resting oxygen saturation was 96% with desaturation to 89% during a 6-min walk test. By visit 2, 19 days later, spirometry had improved (FEV₁ 88%, FVC 86%).

Figure 5.

Pulmonary function (% predicted) over time.

Differential diagnosis

Based on our patient’s initial history of fatigue, malaise and breathlessness together with his CXR, we considered interstitial lung disease as the most likely diagnosis, notably feather-induced HP, but also sarcoidosis and rarer forms of interstitial lung disease. The positive avian precipitin results supported the diagnosis of HP.

Other differential diagnosis included other inflammatory lung diseases such as cryptogenic organising pneumonia, eosinophilic pneumonia and pulmonary vasculitis. However, the CT scan images were not typical. Blood results excluded vasculitis and the serum eosinophil count were low, making eosinophilic pneumonia less likely. Pulmonary embolic disease was also considered but excluded following a CT pulmonary angiogram. Atypical infection such as pneumocystis jiroveci was considered given the presence of ground glass shadowing with a mosaic pattern in both lungs, but there was no acute phase response to support this.

Treatment

At the time of our initial (telephone) contact and prior to more detailed clinical assessment including CT imaging, we advised our patient to remove feather bedding from his bedroom. This was based on his history and CXR alone. We also advised him to get his bathroom mould treated and check there were no nesting birds in his loft or chimney. Given his lung function was significantly impaired we opted to treat him empirically with oral corticosteroids: prednisolone 40 mg once daily for 1 month, reducing every 2 weeks (30, 20, 15 mg) until reaching a maintenance dose of 10 mg once daily. We started omeprazole for gastroprotection and arranged a baseline bone mineral density scan (in case he was going to need prolonged corticosteroid therapy).

Outcome and follow-up

His symptoms improved rapidly within the first month, even before starting oral corticosteroids. By 6 months, he felt completely well. This clinical improvement was mirrored by serial lung function tests (figure 5) and CXRs.

Discussion

HP is an immunologically mediated form of hypersensitivity reaction, caused by repeated inhalation of and sensitisation to finely dispersed antigens. It is a respiratory syndrome, involving the lung parenchyma and specifically the alveoli, terminal bronchioles and alveolar interstitium, due to a delayed allergic reaction.³

Bird fancier’s lung (BFL) is the most common type of HP with an estimated prevalence in pigeon breeders of 6%–20% in exposed individuals, and for budgerigar fanciers 0.5%–7.5%.⁴ FDL is a rare subgroup of BFL, caused by inhalation of organic dust from duck or goose feathers in duvets or pillows.⁵ The prevalence of feather duvet related HP is difficult to determine, given the disease is often unrecognised or misdiagnosed.⁴

The disease progression in HP can be categorised into acute, subacute and chronic. Following the exposure to provoking antigen, the initial dominant reaction seen in acute HP is immune complex mediated, which is a type III hypersensitivity reaction.⁶ Type IV hypersensitivity reaction, which is a delayed hypersensitivity reaction, develops due to continual exposure of the offending antigen and progresses into subacute or chronic forms of HP.⁶ Chemokines and proinflammatory cytokines that are by-products of the hypersensitivity reaction, subsequently mediate a sustained CD8 cytotoxic T-cell response, resulting in ongoing macrophage activation, granuloma formation and fibrosis.⁶ Studies have suggested a genetic link, with major histocompatibility complex haplotypes increasing an individual’s susceptibility to developing HP.⁷

The onset of symptoms following exposure to new feather duvets or pillows is widely variable, ranging from 3 weeks to 5 years.² Dyspnoea is common and patients can also experience other symptoms such as night sweats, dry cough, weight loss and fever.² Clinical findings include tachypnoea, hypoxia, end-inspiratory ‘squeaks’ and fine lung crackles.⁸ The best diagnostic clue is the correlation of symptoms with environmental exposure, given there are no highly specific symptoms or signs.

Blood tests can be helpful, particularly the detection of antigen-specific IgG antibodies against duck or goose feathers. However, a positive test result may simply mean exposure to an antigen, and not actual disease.⁶ Koschel et al demonstrated that specific IgG antibodies against goose feathers are significantly higher in patients with FDL (93.90±52.73 mg/L) than that in patient with BFL (57.57±39.85 mg/L).⁹ Antibodies against duck feathers are elevated in FDL and BFL as well, but the difference between both groups was not significant.⁹

Pulmonary function tests typically demonstrate impaired gas exchange and, in more severe disease, restrictive spirometry.² High-resolution CT is extremely helpful, but appearances vary depending on the stage of the disease.⁶ In the acute phase, ‘ground glass’ shadowing can be seen. This depends on when the scan was taken in relation to the dust exposure.^{6 10} Subacute HP is more classically associated with centrilobular ground glass or nodular opacities with air-trapping, and may show mild fibrosis in the mid to upper portion of the lung lobes.¹¹ Emphysematous and fibrotic changes including honeycombing are seen in chronic HP and are not surprisingly associated with a poorer outcome. It can be confused with idiopathic pulmonary fibrosis.¹²

Bronchoscopy with bronchoalveolar lavage (BAL) can be performed if there is doubt about the diagnosis. Bronchoscopy and BAL were not performed in our case as the clinical diagnosis was felt to be reasonably secure. Typically, BAL in patients with HP demonstrates lymphocytosis, with a low CD4:CD8 ratio.¹³ However, this finding is not specific to HP and can be seen in other conditions. Hence, it is regarded as supportive, rather than diagnostic information.⁶

Given its heterogeneous and non-specific presentation, HP is often challenging to diagnose. The key is taking a meticulous history.³ For the clinician, it is nonetheless satisfying to treat, since in most cases of HP it can be treated by ceasing exposure to the offending antigen. In our patient, we elected to treat with a brief course of oral corticosteroid because of the severity of his symptoms with impaired lung physiology. It is likely that he would have recovered (perhaps less quickly) simply by avoiding feather bedding.

The use of steroids in treating HP is debatable as there were no changes in both lung function and gas transfer observed in children with HP.¹⁴ However, in adults with acute phase of farmer’s lung-related HP, the improvement of pulmonary function was more rapid in corticosteroid-treated group comparing to placebo group.¹⁵

Patient’s perspective.

Hypersensitivity pneumonitis has had a great effect on my life at the time. I started getting dizzy spells on exertion. There was a rapid decline in my health and the lack of a diagnosis after four appointments at the GP surgery was extremely distressing at the time. Two months after the onset of the symptoms, I was unable to stand or walk for more than a few minutes at a time without feeling like I was going to pass out. Going upstairs to bed was a 30 min activity as I could only manage two stairs at a time and then needed to sit and rest. I was signed off work and spent most of the time asleep (day and night).

I am extremely grateful to my local GP for immediately referring my case to OJD who quickly diagnosed me with hypersensitivity pneumonitis. I understand that it is an allergic reaction in my lungs to something breathed in. This reaction has caused my lungs to have reduced efficiency at oxygenating my blood, causing extreme light-headedness.

The steroids which were prescribed after diagnosis by OJD had a transformative effect within 2 days. At the same time, having assumed that a possible cause of the allergy was feather bedding, I replaced them with hypoallergenic bedding. The course of steroids continued ultimately for 12 months, with a gradual reduction in dose over time. I have thankfully been able to stop them completely. My oxygen saturation level nowadays is regularly 97%–98% which I understand to be normal for someone my age, and I have not had any dizzy turns since recovering. It doesn’t affect me at all now and my life is pretty much as it was before.

Learning points.

• The absence of bird exposure at home does not exclude the possibility of bird fancier’s lung disease.

• Healthcare professionals should always ask about whether there is any exposure to feather bedding.

• Accurate diagnosis requires the integration of a meticulous history with relevant clinical data (radiology, physiology and sometimes cytology/pathology).

• Early recognition of avian antigen exposure and removal from this may prevent the development of progressive and potentially irreversible lung fibrosis.