Idiopathic pulmonary fibrosis misdiagnosed as sputum-negative pulmonary tuberculosis.

Idiopathic pulmonary fibrosis (IPF), also known as cryptogenic fibrosing alveolitis, is one of a spectrum of idiopathic interstitial pneumonia. IPF is an increasingly common condition which poses many diagnostic and therapeutic challenges leading to misdiagnosis and mismanagement. We presented a 55-year-old male textile trader who was initially managed as sputum-negative pulmonary tuberculosis before histology report. He presented to our clinic with Breathlessness and cough of 3 years and 2.5 years, respectively. He had commenced anti-tuberculosis two months before presentation without significant relief. General Physical examination and vital signs were essentially normal. SPO2 was 96% on room air. Chest Examination revealed end-inspiratory bi-basal velcro-like crackles. Other systemic examinations were normal. Radiological examination by way of chest X- ray and chest CT showed features suggestive of IPF. The patient also had open Lung biopsy for histology and spirometry which demonstrated restrictive ventilatory function pattern. A diagnosis of Interstitial lung disease probably Idiopathic Pulmonary Fibrosis was entertained. He was commenced on Tab prednisolone, Tab Rabeprazole, with minimal improvement. IPF have often been misdiagnosed and treated as pulmonary tuberculosis with unfavorable outcome.

Introduction

Idiopathic pulmonary fibrosis (IPF) is a form of interstitial lung disease with obscured etiology and the most common primary interstitial pneumonia.[1] IPF is a lung parenchyma disorder with little or no extrapulmonary manifestation.[1]

The index case report is that of an adult diagnosed with IPF, who was initially treated for pulmonary tuberculosis without therapeutic response. Furthermore, this case has brought to fore diagnostic and therapeutic challenges of IPF and the need for proper evaluation.

Case Report

This is a case report of a 55-year-old male textile trader who presented with complaints of breathlessness and dry cough of 3 and 2.5 years, respectively. The patient commenced antituberculosis two months before presentation, with no significant symptomatic relief. General physical examination was unremarkable. Vital signs were stable with SPO2 of 96% on room air. Significant chest examination finding was end-inspiratory bi-basal Velcro-like crackles. Other systemic examinations were essentially normal.

The patient's chest X-ray report showed streaky and patchy opacities mainly in the lower zone bilaterally [Figure 1]. Furthermore, the patient had a chest computed tomography (CT), report of which revealed extensive tiny nodular opacities of soft-tissue density involving the entire lung fields [Figure 2]. Lung function test showed a restrictive pattern with forced expiratory volume in 1 s (FEV1) (% predicted), forced vital capacity (FVC) (% predicted), and FEV1/FVC (% predicted) of 2.63 (3.21), 2.64 (3.92), and 99.77 (79.11), respectively.

Figure 1

Anterior-posterior chest X-ray with bilateral lower zone opacities

Figure 2

Axial chest computed tomography slide showing peripheral ground glass appearance with honeycombing

Following the radiological evaluation, tissue diagnosis was pursued with lung biopsy histology report showing moderate infiltration of the lung parenchyma by lymphocyte with associated patchy interstitial fibrosis and adjacent areas of normal lung tissue [Figure 3a and b].

Figure 3

(a) Inflammatory cell foci and adjacent normal lung parenchyma. (b) High magnification showing foci of inflammatory cell with adjacent normal lung parenchyma

After the complete evaluation, a diagnosis of interstitial lung disease, probably IPF, was entertained. He was commenced on tablet prednisolone 1 mg/kg daily, tablet rabeprazole 40 mg 12 hourly, and bone support with minimal improvement.

Discussion

Clinical evaluation of the index case has re-emphasized the challenges that come with the diagnosis of IPF, especially in developing countries.[2] A case series in Nigeria revealed 28.9% of 45 patients with diffuse radiological pulmonary infiltrate had cryptogenic fibrosing alveolitis, some of which were mismanaged as tuberculosis.[3] There are also reported cases of IPF, some of which were initially managed as cases of smear-negative pulmonary tuberculosis.[24]

The International Consensus Statement on IPF of 2000 and the American Thoracic Society/European Respiratory Society Consensus Classification of 2002 has established criteria for the diagnosis of IPF, which was met in the index case.[1] However, IPF is a clinical entity that can mimic other causes of pulmonary fibrosis and undistinguishable on the historical basis alone.[23] This diagnostic dilemma played out in the index case when it was misdiagnosed and treated as a case of pulmonary tuberculosis.

IPF typically reveals lower zone involvement with subpleural septal thickening, peripheral interstitial densities with variegation, traction bronchiectasis, honeycombing with minimal ground glass appearance on the chest CT.[1] Usual interstitial pneumonia is the typical histological finding.

Treatment of patients with IPF has been challenging and disappointing. Immunosuppressants and antifibrotic agents have been the mainstay of pharmacological treatment, all of which have produced mixed clinical results.[15] Lung transplant offers a veritable option to obtain a cure of IPF but not readily available.

Conclusion

IPF is associated with diagnostic and therapeutic challenges that have led to the misdiagnosis, improper treatment, and poor outcome. IPF cases have frequently treated as pulmonary tuberculosis.

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Conflicts of interest

There are no conflicts of interest.