Gaining an Understanding of Phlyctenular Keratoconjunctivitis
BY WILLIAM L. MILLER, OD, PHD, FAAO
Phlyctenular keratoconjunctivitis (phlyctenulosis) is an uncommon, type-IV (delayed) hypersensitivity to an antigen that initiates an inflammatory process resulting in conjunctival or corneal nodules (phlyctenules). Although in Greek the word means blister, phlyctenules aren't reminiscent of typical blisters that occur elsewhere on the body. The nodules are instead characterized histopathologically as a conglomeration of lymphocytes, histocytes and plasma cells.
What's Behind Phlyctenulosis?
Most of the time, phlyctenulosis is unilateral, typically occurring in the first two decades of a person's life. Implicated causes for this hypersensitivity reaction include tuberculosis, Staphylococcal aureus, Candida albican, parasites and Chlamydia (more common in young patients who have a recurrent history of phlyctenulosis).
S. aureus causes most cases of phlyctenulosis in the industrialized world, but consider tuberculosis in selected populations that have positive tuberculin skin tests and in patients who travel to developing countries. If a hint of suspicion exists, then refer the patient for a tuberculin skin test and/or chest x-ray.
Recognizing Signs & Symptoms
Typical symptoms found in patients with phlyctenulosis are not unlike those found in other anterior segment anomalies and may include: tearing, foreign body sensation, photophobia, burning and itching, all of which tend to be on the mild to moderate side. If the phlyctenulosis has affected the cornea, expect the symptoms to be more severe.
Signs include an acutely appearing raised, amorphous, pinkish gray nodule(s) typically 1mm to 2mm in diameter. Nodules can occur on the conjunctival (bulbar and limbal) and corneal surface, more commonly appearing near the limbus. After a few days the nodule(s) tends to decrease in size and a central ulcer forms, following a typical pattern of elevation, infiltration and ulceration.
Make a Positive ID
It's important to differentiate phlyctenulosis from other anomalies that may have similar appearances such as Salzmann's corneal degeneration (non-migratory, non-inflamed), Horner-Trantas dots in vernal conjunctivitis (itchiness and discharge), nodular episcleritis (episcleral vessel dilatation) and an inflamed pinguecula (3 o'clock to 9 o'clock positioning). You can distinguish most of these with a careful case history and evidence of nodule migration or movement or other presenting signs (as noted in the preceding paragraphs). The presence of a "wandering" phlyctenule may prove troublesome; it may transit across the cornea, ultimately resting in the visual axis and reducing visual acuity.
Treating the Hypersensitivity
The nodules typically resolve in about two weeks -- depending on the severity of the initial presentation. Base treatment on the suspected causative agent. Typical treatments may include the use of topical steroids or antibiotic-steroid combinations.
If the cornea is involved and symptoms are severe, then have the patient instill prednisolone acetate 1% (Pred Forte, Allergan) topically q.4.h. A course of oral antibiotics, either tetracycline 250mg or doxycycline 100mg may be indicated in severe cases if the suspected antigen vector is Staphylococcal (don't use either antibiotic in children).
Fully explain side effects to adult patients undergoing this regimen. Institute an aggressive oral therapy only in cases of severe Staphylococcal lid infections or after conservative therapy is unsuccessful or lacking.
Dr. Miller is on the faculty at the University of Houston College of Optometry. He is a member of the American Optometric Association and serves on its Journal Review Board. You can reach him at firstname.lastname@example.org.