Extensive "stalagmite" epi-iridic juvenile xanthogranuloma simulating diffuse melanoma in a 16-year-old girl

A 16-year-old girl noted worsening redness and photophobia of the right eye that had previously been treated unsuccessfully with sequential courses of topical antibiotics and topical corticosteroids. Clinical examination revealed diffuse flakelike thickening of the iris surface, pupillary margin, and anterior chamber angle, suggesting diffuse iris melanoma. Anterior segment optical coherence tomography depicted the mass as an epi-iridic deposit with "stalagmite" surface appearance. Fine-needle aspiration biopsy confirmed an atypical histiocytic proliferative disorder consistent with juvenile xanthogranuloma. Aggressive topical corticosteroid treatment was started. There were no systemic findings. Following therapy, the lesion resolved completely.