Cutaneous leishmaniasis is an endemic protozoan infection in Sardinia, one of the major islands of the Mediterranean Basin. The main causative strain in this country is Leishmania infantum, which rarely involves mucocutaneous areas, but has the potential to cause visceral leishmaniasis. An atypical leishmaniasis involving the inferior lip of a 57-year-old female with Down's syndrome was observed at the Dermatology Department of Cagliari (italy). The diagnosis was mainly based upon histopathological examination, revealing intra- and extra-cellular leishmania amastigotes. The leishmania infantum zymodeme MON-111 was identified by isoenzymatic characterization. Laboratory investigations revealed a normal complete blood count and biochemistry profile, except for an inverted CD4/CD8 ratio. Treatment with meglumine antimoniate 60 mg/kg/day (Glucantime®) intramuscularly for 15 days, followed by intralesional administration 1 ml weekly for 4 weeks led to complete recovery. No relapses were observed at 6-month follow-up. The unusual localization is likely to be a reflection of the uncommon site of inoculation of the protozoa, transmitted by bites from flying vectors. Nevertheless, the presence of Down's syndrome in our patient may have contributed to the atypical presentation by traumatic exacerbation of the lesion, due to repeated auto-induced microtraumas of the inferior lip accompanied by subclinical immunodeficiency. In fact, the specific immune response to Leishmania infection depends on a host-cell-mediated immune response, reported as defective in Down's syndrome patients. Differential diagnosis and early detection of the infection are necessary in order to start effective treatment and prevent more serious complications.