Unilateral tuberculous conjunctivitis with tarsal necrosis.

irritation, often in association with dry eyes, cicatrizing diseases, and inflammation. In this patient, cicatricial keratoconjunctivitis, ie, ocular pemphigoid, drug-induced pseudopemphigoid, StevensJohnson syndrome, or chemical burns, was not observed. Moreover, the signs and symptoms did not suggest evidence of other types of chronic keratoconjunctivitis, such as superior limbic keratitis, graftvs-host disease, or atopic keratoconjunctivitis. Systemic vitamin A deficiency is also known to cause squamous metaplasia of the ocular surface, characterized by a Bitôt spot: a superficial, foamy, gray triangular area on the bulbar conjunctiva that appears in the palpebral aperture. This spot consists of keratinized epithelium, inflammatory cells, debris, and Corynebacterium xerosis. Results of conjunctival histologic and impression cytologic analysis suggested that the lesion was a Bitôt spot; however, systemic vitamin A deficiency was ruled out by the laboratory examination. We also suspected that this patient might have local squamous metaplasia at the limbus or nocturnal lagophthalmos with chronic exposure. However, none of this could be proven. Systemiczincdeficiencycanlead to xerosis of the skin. On laboratory examination, it was revealed that this patient had mild zinc deficiency. He was treated with oral zinc supplementation.Zinc isnecessary in traceamounts in thebody,andhence, in the diet. It forms an essential part of many enzymes and plays an important role in protein synthesis and cell division. Zinc deficiency is associated with growth retardation, alopecia, impaired spermatogenesis, impaired wound healing, and hyperkeratosis of the skin. Although the association of zinc with squamous metaplasia of the ocular surface has not been reported yet, zinc deficiency might be a contributory cause of the lesion in this patient. We performed surgical excision of the lesion. The patient responded well to the excision and zinc supplementation, and there has been no recurrence to date. The precise cause of the limbal squamous metaplasia in this patient remains unclear.