© 2020 Southern Society for Clinical Investigation A Mexican 24-year-old male patient was referred to our hospital due to increased left retroauricular volume with skin fistulisation, resembling an infection by the uncommon worm Lagochilascaris minor. The patient was submitted to lateral skull base surgery. No adult worms or eggs were observed during light and scanning electron microscopy analysis, as well as by histopathologic examination of the small piece of removed tissue, only L3 stage larvae of Lagochilascaris spp. were identified. Polymerase chain reaction-sequencing assays were performed using primers for the mitochondrial 12S and the nuclear 18S rDNA gene. DNA of some L minor adults, previously identified, were used as control. The molecular analysis identified the worm as L minor. According to previous reports, lagochilascariasis is a complicated infection that requires an interdisciplinary management by different clinical specialists. This is the first time that 12S and 18S rDNA genes are reported as molecular markers for diagnosis of L minor.