Long-term home parenteral nutrition is associated with increased risk of line infection and subsequent sepsis. Line infections involving rapidly growing mycobacteria are almost exclusively found in immunocompromised patients. The authors report a case of opportunistic line-sepsis caused by Mycobacterium mucogenicum in a home parenteral nutritional patient with overt immunocompromise. Following a prolonged clinical course and molecular sequencing this infection was eventually diagnosed. The importance of awareness of rapidly growing mycobacteria as a causative agent of line infection in both immunocompromised and immunocompetent patients, the need for immediate removal of the line in such diagnosed infections, and the use of molecular techniques to identify atypical pathogens are emphasised. [ABSTRACT FROM AUTHOR]