Letter

Juvenile xanthogranulomas are highly prevalent but transient in young children with neurofibromatosis type 1

El diagnóstico de la neurofibromatosis tipo 1 (NF1) habitualmente se demora en niños sin antecedentes familiares. Nuestro objetivo fue definir la prevalencia y características de las manifestaciones cutáneas prevalentes en la NF1, en comparación con la población general, que siguen siendo excluidas de los criterios diagnósticos para NF1.

Estudio de casos y controles, pareado por grupos de edad, en el que se incluyó a 108 pacientes diagnosticados de NF1 y 137 controles sanos.

La prevalencia de nevus anemicus (NA) (p < 0,001) y xantogranuloma juvenil (XJ) (p < 0,001) fue significativamente superior en la población afectada de NF1, en comparación con el grupo control. Se estimaron una especificidad del 99,27% (intervalo de confianza: 95,4-99,96%) y un valor predictivo positivo (VPP) del 98,80% (92,54-99,94%) para NA, y una especificidad del 99,27% (95,4-99,96%) y VPP del 92,86% (64,17-99,63%) para XJ en el diagnóstico de NF1 en niños que presentan 6 o más manchas café con leche. También se evidenciaron diferencias estadísticamente significativas en la distribución por fototipos (p = 0,025) y con el generalizado sin otra causa conocida (p <,001).

Los NA y los XJ son hallazgos clínicos relevantes para el diagnóstico de NF1, especialmente durante los primeros años de vida. Consideramos que debería evaluarse su inclusión en los criterios diagnósticos de la enfermedad.

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<.001) and juvenile xanthogranulomas (JXG) (P<.001) was significantly higher in the population affected by NF1 than in the control population. A specificity of 99.27% (confidence interval): 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=.025) and in relation to generalized itching with no other cause (P<.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.

By incorporating major developments in genetics, ophthalmology, dermatology, and neuroimaging, to revise the diagnostic criteria for neurofibromatosis type 1 (NF1) and to establish diagnostic criteria for Legius syndrome (LGSS).

We used a multistep process, beginning with a Delphi method involving global experts and subsequently involving non-NF experts, patients, and foundations/patient advocacy groups.

We reached consensus on the minimal clinical and genetic criteria for diagnosing and differentiating NF1 and LGSS, which have phenotypic overlap in young patients with pigmentary findings. Criteria for the mosaic forms of these conditions are also recommended.

The revised criteria for NF1 incorporate new clinical features and genetic testing, whereas the criteria for LGSS were created to differentiate the two conditions. It is likely that continued refinement of these new criteria will be necessary as investigators (1) study the diagnostic properties of the revised criteria, (2) reconsider criteria not included in this process, and (3) identify new clinical and other features of these conditions. For this reason, we propose an initiative to update periodically the diagnostic criteria for NF1 and LGSS.

Neurofibromatosis type 1 (NF-1) predisposes individuals to the development of benign and malignant tumors. The association of NF-1, juvenile xanthogranuloma (JXG), and juvenile myelomonocytic leukemia has been described in the literature. It is unclear whether JXG alone constitute a risk factor for leukemia or other malignancies in children with NF-1.

To determine if there is an association between NF-1, JXG, and malignancy.

We conducted a retrospective case-control study comparing children with NF-1 and malignancy (cases) with sex- and age-matched children with NF-1 without malignancy (controls).

We identified 739 patients with NF-1 over a 20-year period, 14 of whom also had a diagnosis of malignancy. These cases include 9 (64%) boys and 5 (36%) girls. JXG were found in 4/14 (28.5%) cases and 6/29 (21%) controls (odds ratio 1.5, 95% confidence interval 0.35-6.6, P = .56).

Retrospective design, small number of cases, and inconsistent documentation of clinical findings, including age at disappearance of JXG.

Juvenile xanthogranulomas do not appear to confer an increased risk for malignancy in children with NF-1.