Congenital Giant Juvenile Xanthogranuloma, Let It Be.

Description Juvenile xanthogranuloma (JXG) is a rare type of non-Langerhans cell histiocytosis. JXGs are benign and have a self-limiting course generally lasting 6 months to 3 years, with some reported durations longer than 6 years. We present a rarer congenital giant variant, defined as lesions with a diameter larger than 2 cm. It is uncertain if the natural history of giant xanthogranulomas is similar to the usual JXG. We followed a 5-month-old patient with a 3.5 cm in diameter, histopathologically-confirmed, congenital, giant JXG located on the right side of her upper back. The patient was seen every 6 months for 2.5 years. At 1 year of age, the lesion had decreased in size, lightened in color, and was less firm. At 1.5 years old, the lesion had flattened. By 3 years old, the lesion had resolved but left a hyperpigmented patch with a scar at the punch biopsy site. Our case represents a congenital giant JXG that was biopsied to confirm the diagnosis and then monitored until resolution. This case supports the clinical course of giant JXG not being affected by the larger lesion size and that aggressive treatments or procedures are not warranted.