A Case Report on a Challenge From Diagnosis to Treatment: Interstitial Lung Disease As the First Manifestation of Systemic Sclerosis Sine Scleroderma

Interstitial lung disease comprises a heterogeneous group of conditions that may progress to pulmonary fibrosis. Establishing an accurate etiology is critical, as it dictates specific immunomodulatory therapy and profoundly influences prognosis. Systemic sclerosis is a rare autoimmune condition frequently complicated by interstitial lung disease, either during its course or, less commonly, as its initial or sole manifestation. Diagnosing systemic sclerosis in the absence of typical scleroderma features can be particularly challenging. We present a rare case of pulmonary involvement as the initial manifestation of systemic sclerosis sine scleroderma. A man in his 70s presented to the Emergency Department due to gradually increasing dyspnea over the preceding two months. Upon admission, he was found to have hypoxemic respiratory failure. Thoracic computed tomography showed a fibrotic pulmonary pattern characterized by peripheral reticulation, honeycombing, and traction bronchiectasis. Bronchoscopy with bronchoalveolar lavage showed intense neutrophilic and mild eosinophilic alveolitis, along with increased alveolar macrophages. Initial clinical improvement was observed following treatment with corticosteroids and antibiotics, as infection could not be excluded. Following discharge and corticosteroid tapering, the patient's clinical condition worsened. Further immunological evaluation revealed positive antinuclear, anti-centromere, and RNA polymerase III antibodies. Pulmonary function tests demonstrated a mild restrictive pattern and a severely reduced diffusing capacity for carbon monoxide. In the absence of overt scleroderma or vasculopathy, a diagnosis of interstitial lung disease associated with systemic sclerosis sine scleroderma was established. Treatment with mycophenolate mofetil was initiated, and later combined with nintedanib, resulting in initial disease stabilization. Unfortunately, the patient succumbed to progressive and complicated pulmonary disease two years after initial presentation. This case underscores the importance of maintaining a high index of suspicion when evaluating patients with interstitial lung disease, even in the absence of cutaneous manifestations of systemic sclerosis.