Congenital cutaneous neurofibromas in neurofibromatosis type 1: Clinicopathological features in early infancy

Clinical and Sonographic Classification of Neurofibromas in Children with Neurofibromatosis Type 1 - A Cluster Analysis

PURPOSE

 High-frequency ultrasound allows the accurate identification of neurofibromas in neurofibromatosis type 1 (NF1). This study aimed to analyze the ultrasound features of neurofibromas in children with NF1, to establish a classification based on the clinical and sonographic patterns of the different types of neurofibromas, and to evaluate the interobserver correlation coefficient (κ) of this classification.

MATERIALS AND METHODS

 In this prospective, single referral center observational study, clinical and ultrasound findings of neurofibromas in children diagnosed with NF 1 were analyzed. To identify the ultrasound patterns, a cluster analysis allowing the inclusion of both clinical and ultrasound data was designed. The κ coefficient was calculated using 9 external evaluators.

RESULTS

 265 ultrasound scans were performed on a total of 242 neurofibromas from 108 children diagnosed with NF1. Cluster analysis allowed the identification of 9 patterns (Snedecor's F, P < 0.001) classified as "classic" cutaneous neurofibroma, blue-red neurofibroma, pseudoatrophic neurofibroma, nodular subcutaneous neurofibroma, diffuse subcutaneous neurofibroma, congenital cutaneous neurofibroma, congenital plexiform neurofibroma, congenital diffuse and plexiform neurofibroma, and subfascial neurofibroma. The κ coefficient of the interobserver ratings was 0.82.

CONCLUSION

 Patterns identified in the cluster analysis allow neurofibromas to be classified with a very high interobserver correlation.

Neurofibromatosis Type 1: Diagnostic Timelines in Children

BACKGROUND AND OBJECTIVES

The neurofibromatosis 1 (NF1) diagnosis is challenging in young children without a family history of NF1. The aims of this study were to estimate diagnostic delays in children without a family history of NF1 and to examine the effects of using café au lait macules and skin fold freckling as a single diagnostic criterion.

PATIENTS AND METHODS

Retrospective, descriptive, observational study of all patients diagnosed with NF1 before the age of 18 years who were seen at our hospital. The medical records of those included were reviewed to identify the date on which the diagnostic criteria of NF1 were objectified. The patients were categorized into 2 groups: those with a known parental history of NF1 and those without. Café au lait macules and skin fold freckling were assessed as a single diagnostic criterion, and genetic evidence was considered to confirm highly suspicious cases.

RESULTS

We studied 108 patients younger than the age of 18 years with a diagnosis of NF1. Mean (SD) age at diagnosis was 3.94 (±3.8) years for the overall group, 1 year for patients with a parental history of NF1, and 4 years and 8 months for those without. Diagnosis was therefore delayed by 3 years and 8 months in patients without a family history.

CONCLUSION

Skin lesions were the first clinical manifestation of NF1 in most patients. We believe that the National Institutes of Health's diagnostic criteria for NF1 should be updated to aid diagnosis in young children.

[Translated article] Neurofibromatosis Type 1: Diagnostic Timelines in Children

BACKGROUND AND OBJECTIVES

Diagnosis of neurofibromatosis 1 (NF1) diagnosis is challenging in young children without a family history of NF1. The aims of this study were to estimate diagnostic delays in children without a family history of NF1 and to examine the effects of considering café-au-lait macules and skinfold freckling as a single diagnostic criterion.

PATIENTS AND METHODS

Retrospective, descriptive, observational study of all patients diagnosed with NF1 before the age of 18 years who were seen at our hospital. The medical records of those included were reviewed to identify the date on which the diagnostic criteria of NF1 were objectified. The patients were categorized into 2 groups: those with a known parental history of NF1 and those without. Café-au-lait macules and skinfold freckling were assessed as a single diagnostic criterion, and genetic evidence was considered to confirm highly suspicious cases.

RESULTS

We studied 108 patients younger than the age of 18 years with a diagnosis of NF1. Mean (SD) age at diagnosis was 3.94 (±3.8) years for the overall group, 1 year for patients with a parental history of NF1, and 4 years and 8 months for those without. Diagnosis was therefore delayed by 3 years and 8 months in patients without a family history.

CONCLUSION

Skin lesions were the first clinical manifestation of NF1 in most patients. We believe that the National Institutes of Health's diagnostic criteria for NF1 should be updated to aid diagnosis in young children.

New-onset cutaneous nodule arising from hypertrichotic brownish patch in a 6-year-old girl

A 6-year-old girl presented with an enlarging asymptomatic nodule within a hyperpigmented hypertrichotic patch on her left thigh. Histopathological examination revealed tumour cells with round to fusiform nuclei in a fine fibrillary collagenous stroma, along with increased cellularity. Most of the tumour cells were positive for S-100 and negative for HMB-45 and Melan-A.

Das NF1-Mikrodeletions-Syndrom: Die frühzeitige genetische Diagnose erleichtert den Umgang mit einer klinisch definierten Erkrankung

Neurofibromatose Typ-1 (NF1) ist ein Genodermatose, die häufig in der Dermatologie behandelt wird. Bei vielen Patienten mit NF1 wird die Diagnose aufgrund klinischer Merkmale erstellt wie Café-au-Lait-Flecken, Freckling und plexiformen Neurofibromen, die schon während der frühen Kindheit auftreten können. Später im Leben sind oft kutane Neurofibrome weitere wichtige diagnostische Merkmale. Die NF1 ist durch ausgeprägte klinische Variabilität und eine breite Heterogenität der NF1-Genmutationen charakterisiert, was Genotyp/Phänotyp-Korrelationen erschwert. Wichtige Ausnahmen sind NF1-Mikrodeletionen, die bei 5-11 % aller NF1-Patienten auftreten. Patienten mit NF1-Mikrodeletionen zeigen häufig spezifische Merkmale wie Gesichtsdysmorphien und sind von großer Statur. Zudem sind früh auftretende kutane und subkutane Neurofibrome, schwere Entwicklungsverzögerungen in multiplen Bereichen sowie kognitive Einschränkungen pathognomonisch für das NF1-Mikrodeletions-Syndrom. Darüber hinaus sind NF1-Mikrodeletionen mit einem Risiko für maligne periphere Nervenscheidentumoren assoziiert, das etwa zweifach höher ist als bei intragenischen NF1-Mutationen. Die schweren klinischen Manifestationen bei Patienten mit NF1-Mikrodeletionen machen eine frühe multidisziplinäre klinische Betreuung und häufige Tumor-Überwachung der Patienten notwendig. Wenn bei einem Patienten Red-Flag-Symptome für das NF1-Mikrodeletions-Syndrom auftreten, ist eine frühzeitige genetische Untersuchung notwendig, um eine NF1-Mikrodeletion zu bestätigen oder auszuschließen.

The NF1 microdeletion syndrome: early genetic diagnosis facilitates the management of a clinically defined disease

Neurofibromatosis type-1 (NF1) is a genodermatosis frequently encountered in general dermatology. In many patients, the diagnosis of NF1 is made clinically based on the presence of café-au-lait macules and skinfold freckling, as well as plexiform neurofibromas detectable during early childhood. Later in life, cutaneous neurofibromas often represent important diagnostic features. NF1 is characterized by extreme clinical variability and a broad heterogeneity of NF1 gene mutations which impede genotype/phenotype correlations. Notable exceptions are NF1 microdeletions observed in 5-11 % of all NF1 patients. Patients with NF1 microdeletions frequently exhibit facial dysmorphic features and a tall stature as rather specific clinical signs. Furthermore, cutaneous and subcutaneous neurofibromas present at an early age, severe global developmental delay and cognitive disability are pathognomonic for the "NF1 microdeletion syndrome". Importantly, NF1 microdeletions are associated with an approximately twofold higher risk for malignant peripheral nerve sheath tumors than intragenic NF1 gene mutations. The severe clinical manifestations of patients with NF1 microdeletions require early multidisciplinary clinical care and frequent tumor surveillance. Therefore, when red flag features for the "NF1 microdeletion syndrome" are present in a patient, genetic testing is necessary to confirm or exclude an NF1 microdeletion.

Challenges in the diagnosis of neurofibromatosis type 1 (NF1) in young children facilitated by means of revised diagnostic criteria including genetic testing for pathogenic NF1 gene variants

Neurofibromatosis type 1 (NF1) is the most frequent disorder associated with multiple café-au-lait macules (CALM) which may either be present at birth or appear during the first year of life. Other NF1-associated features such as skin-fold freckling and Lisch nodules occur later during childhood whereas dermal neurofibromas are rare in young children and usually only arise during early adulthood. The NIH clinical diagnostic criteria for NF1, established in 1988, include the most common NF1-associated features. Since many of these features are age-dependent, arriving at a definitive diagnosis of NF1 by employing these criteria may not be possible in infancy if CALM are the only clinical feature evident. Indeed, approximately 46% of patients who are diagnosed with NF1 later in life do not meet the NIH diagnostic criteria by the age of 1 year. Further, the 1988 diagnostic criteria for NF1 are not specific enough to distinguish NF1 from other related disorders such as Legius syndrome. In this review, we outline the challenges faced in diagnosing NF1 in young children, and evaluate the utility of the recently revised (2021) diagnostic criteria for NF1, which include the presence of pathogenic variants in the NF1 gene and choroidal anomalies, for achieving an early and accurate diagnosis.