A 43-year-old man of Middle Eastern descent had a 1-week history of blurred vision in the right eye. He and several siblings had a history of recurrent oral thrush but no diagnosed immunodeficiency. He had no history of intravenous drug abuse or recent symptoms of oral thrush. On examination, vision in the affected eye was 20/200. A 1.5-mm focal white retinal infiltrate was seen along the superior-temporal arcade with neurosensory macular detachment. He was treated with a varying regimen of sulfadiazine, daraprim, leucovorin calcium, clindamycin hydrochloride, and prednisone in the ensuing 7 weeks (Figure 1A). Results of rapid plasma reagin, fluorescent treponemal antibody absorption, human immunodeficiency virus enzyme-linked immunosorbent assay, blood cultures, and Bartonella and anti-Toxoplasma IgG and IgM titers were either within the normal range or negative. Five weeks after the patient's initial visit, his visual acuity decreased and the retinal lesion was nearly twice its original size (Figure 1B). The prednisone dosage was increased but the lesion continued to enlarge (Figure 1C). Vitrectomy performed 7 weeks after his initial visit revealed yeasts and pseudohyphae on Gram staining. At the conclusion of surgery, 50 μg of voriconazole in 0.1 mL of sterile water was injected intravitreously. Cultures grew Candida albicans sensitive to voriconazole and fluconazole. Oral voriconazole at a dosage of 200 to 300 mg by mouth twice a day and later oral fluconazole at a dosage of 800 mg by mouth daily failed to slow progression. Treatment with intravitreous voriconazole at a dose of 100 μg in 0.1 mL of sterile water was started, but the lesion progressed despite 6 more injections every 3 to 4 days during the next month. A second pars plana vitrectomy with excision of the entire white lesion in the macula was followed by endolaser and gas-fluid exchange. Cultures yielded Candida albicans still sensitive to voriconazole and fluconazole. Urine and blood culture results were negative. Postoperatively, the patient was treated with intravenous fluconazole and micafungin. Further studies were performed, including transesophageal echocardiography, lymphocyte subset analysis, thyroid stimulation hormone level, serum cortisol level, and lumbar puncture with cerebral spinal fluid analysis and culture, all of which had unremarkable results. The patient was not anergic to a Candida skin test; lymphocyte transformation to Candida antigen and neutrophil function test results were normal. One month later, a new retinal infiltrate was seen in the midperiphery, followed by a second focus the next week. The patient received a series of 16 injections of intravitreous voriconazole every 1 to 3 days with alternating doses of 100 μg and 200 μg in 0.1 mL of sterile water. Four satellite lesions developed, followed by a partial retinal detachment, lens capsular opacification, and anterior chamber inflammation. The left eye remained healthy. The affected eye was enucleated and examined histologically in its entirety. The specimen revealed persistent growth of yeasts in the cortical vitreous (Figure 2). Extensive testing of immune function disclosed a severe deficiency of MBL (6 ng/mL; reference range, ≥100 ng/mL]).