“…subcutaneous emphysema) constitute very rare acute respiratory events in CTDs and may occur simultaneously or in isolation. They have been described in the literature in a variety of case reports concerning each one of the major seven CTDs, and very scarcely do they represent spontaneous events or events at initial presentation of the disease [154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169]. Most of the times, they are secondary to a preexisting chronic lung disease such as ILD with subpleural cystic-honeycombing lesions, especially in RA, scleroderma, DM-PM, and mixed connective tissue disease; the presence of peripheral necrobiotic lung nodules in RA, cystic lung disease or lower respiratory tract infections in SLE and Sjögren's syndrome, and fibrobullous disease of the lungs in ankylosing spondylitis further increases the risk of their development and aggravates their outcome.…”