Abstract Background Down syndrome (DS) or Trisomy 21 is the most common chromosomal disease and is characterized by possible heart defects, cognitive impairment and visual disorders. Case presentation We describe for the first time a 17-year-old Caucasian girl suffering from Down syndrome associated with vernal keratoconjunctivitis (VKC), a rare disorder of the anterior segment of the eye, characterized by intense photophobia, redness, watering eyes and itching due to an inflammatory-allergic reaction of the cornea and conjunctiva. On slit-lamp examination, the girl showed conjunctival hyperemia, papillary hypertrophy, giant papillae and corneal leukoma in right eye as a result of a previous corneal ulcer. A successful topical immunosuppressant therapy with cyclosporin 1% was started. Conclusion So far, to our knowledge, this is the first description of VKC in a patient with DS. Finding an inflammatory-allergic disease such as VKC in DS is unusual but it must be taken into account because keratoconus, one of the most frequent eye pathologies in DS, can be secondary to an unrecognized VKC.