151 Clinical Course | Crouzon AN INTRODUCTION Crouzon syndrome accompanied by acanthosis nigricans, a specific skin disorder of hyperkeratosis and hyperpigmentation, represents a clinically and genetically rare entity distinct from the classic Crouzon syndrome and is caused by the mutation c.1172C>A (p.Ala391Glu) in the fibroblast growth factor receptor 3 gene (FGFR3; Figure 1).1 The skin disorder typically occurs later in life. Figure 1. Photograph of mother and son both with a confirmed c.1172C>A (p.Ala391Glu) mutation in the FGFR3 gene. The combination of Crouzon syndrome with acanthosis nigricans (CAN) was first described by Suslak et al. and Reddy et al. in 1985.2, 3 In 1995 Meyers et al. reported the first observation of an FGFR3 transmembrane domain mutation, Ala391Glu, in three unrelated families with CAN.1 An overview of 33 published cases of CAN revealed that 39.4% (13/33 cases) presented with choanal atresia at birth, 45.5% (15/33 cases) developed hydrocephalus, and 24.2% (8/33 cases) developed Chiari malformation. In 15.2% (5/33 cases), intellectual impairment and speech delay were present.4 According to Arnaud-López, CAN patients are clinically more severely affected than Crouzon patients without the skin disorder, whereas mental development in CAN patients seems to be preserved.4 9
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