Diagnostic delay of NF1 in hemifacial hypertrophy due to plexiform neurofibromas

Benign tumors of the peripheral nerve sheath, termed neurofibromas, are the hallmark feature of neurofibromatosis type 1 (NF1). These tumors can result in hypertrophy of a limb or another anatomic region. Hemifacial hypertrophy due to an underlying neurofibroma is a typical manifestation of NF1 in young children although the overall frequency of facial involvement is low. We retrospectively studied all patients, which were referred to our outpatient clinic because of hemihypertrophy or swelling of the face for initially unknown reason with a final diagnosis of NF1. A total number of six patients were identified. Clinical and radiological characteristics of these patients were analyzed. In all patients, diagnosis of NF1 could be established based on the typical clinical criteria. However, despite other typical NF1-associated features (e.g. multiple café-au-lait spots) diagnosis of a plexiform neurofibroma as underlying cause for the hemifacial hypertrophy was significantly delayed in all patients. MRI scans were misinterpreted in all of the cases as lymphangioma because plexiform neurofibromas can resemble mesenchymal tumors or lymphangiomas. NF1 has to be considered in the differential diagnosis of hemifacial hypertrophy. A thorough clinical examination of affected patients should focus on typical disease-defining features. Early diagnosis of NF1 can prevent unnecessary treatment at least in some patients.