Cutaneous Manifestations not Considered Diagnostic Criteria for Neurofibromatosis Type 1. A Case-Control Study

The diagnosis of Neurofibromatosis type 1 (NF1) is usually delayed in children without a family history. We aimed to define the prevalence and characteristics of prevalent skin manifestations in NF1 compared to the general population, which continue to be excluded from the diagnostic criteria for NF1.

Case-control study, matched by age groups, in which 108 patients with a diagnosis of NF1 and 137 healthy controls were included.

The prevalence of nevus anemicus (NA) (p<0.001) and juvenile xanthogranulomas (JXG) (p<0.001) was significantly higher in the population affected by NF1 than in the control population. A specificity of 99.27% [confidence interval (CI): 95.4-99.96%] and a positive predictive value (PPV) of 98.80% [92.54-99.94%] were estimated for NA and a specificity of 99.27% [95.4-99.96%] and a PPV of 92.86% [64.17-99.63%] for JXG in the diagnosis of NF1 in children who present 6 or more Café-au-lait macules. Statistically significant differences were also evidenced in the distribution by phototypes (p 0.025) and in relation to generalized itching with no other cause (p<0.001).

NA and JXG are relevant clinical findings for the diagnosis of NF1, especially during the first years of life. We consider that its inclusion among the diagnostic criteria of the disease should be evaluated.