Context : HD 50138 presents the B [ e ] phenomenon , but its nature is not clear yet .
This star is known to present spectral variations , which have been associated with outbursts and shell phases .

Aims : We analyze the line profile variability of HD 50138 and its possible origin , which provide possible hints to its evolutionary stage , so far said to be close to the end of ( or slightly beyond ) the main sequence .

Methods : New high-resolution spectra of HD 50138 obtained with the HERMES spectrograph over several nights ( five of them consecutively ) were analyzed , allowing us to confirm short-term line profile variability .

Results : Our new data show short-term variations in the photospheric lines .
On the other hand , purely circumstellar lines ( such as [ O i ] lines ) do not show such rapid variability .
The rotational velocity of HD 50138 , \varv _ { rot } = 90.3 \pm 4.3 km s ^ { -1 } , and the rotation period , P = 3.64 \pm 1.16 d , were derived from the He i \lambda 4026 photospheric line .
Based on the moment method , we confirm that the origin of this short-term line profile variability is not stellar spots , and it may be caused by pulsations .
In addition , we show that macroturbulence may affect the profiles of photospheric lines , as is seen for B supergiants .

Conclusions : The location of HD 50138 at the end of ( or slightly beyond ) the main sequence , the newly detected presence of line profile variability resembling pulsating stars , and macroturbulence make this star a fascinating object .