What is the most likely diagnosis for a 63-year-old woman with CREST syndrome and bilateral basal crackles?

The most likely diagnosis for a 63-year-old woman with CREST syndrome and bilateral basal crackles is interstitial lung disease. CREST syndrome, which is a limited form of systemic sclerosis (scleroderma), is often associated with various pulmonary complications, particularly interstitial lung disease. This condition encompasses a group of disorders that cause progressive scarring of lung tissue, leading to impaired gas exchange and respiratory symptoms.

Bilateral crackles, particularly when they are heard at the bases of the lungs, are characteristic of interstitial lung diseases where the lung parenchyma becomes fibrotic, causing a stiff lung that is harder to ventilate. In the context of CREST syndrome, many patients develop pulmonary fibrosis, which is a specific form of interstitial lung disease.

While other conditions such as cryptogenic organising pneumonia and tuberculosis could present with respiratory symptoms and crackles, their association with CREST syndrome is not as strong. Progressive massive fibrosis is more commonly linked to significant exposure to coal dust or silica and is not a direct consequence of CREST syndrome. Thus, interstitial lung disease is the most likely and relevant diagnosis given the patient’s systemic condition and pulmonary findings.