Elevated head circumference-to-height ratio is an early and frequent feature in children with neurofibromatosis type 1

Neurofibromatosis Type 1: Pediatric Aspects and Review of Genotype-Phenotype Correlations

Neurofibromatosis type 1 (NF1) is an autosomal dominant condition, with a birth incidence of approximately 1:2000-3000, caused by germline pathogenic variants in NF1, a tumor suppressor gene encoding neurofibromin, a negative regulator of the RAS/MAPK pathway. This explains why NF1 is included in the group of RASopathies and shares several clinical features with Noonan syndrome. Here, we describe the main clinical characteristics and complications associated with NF1, particularly those occurring in pediatric age. NF1 has complete penetrance and shows wide inter- and intrafamilial phenotypic variability and age-dependent appearance of manifestations. Clinical presentation and history of NF1 are multisystemic and highly unpredictable, especially in the first years of life when penetrance is still incomplete. In this scenario of extreme phenotypic variability, some genotype-phenotype associations need to be taken into consideration, as they strongly impact on genetic counseling and prognostication of the disease. We provide a synthetic review, based on the most recent literature data, of all known genotype-phenotype correlations from a genetic and clinical perspective. Molecular diagnosis is fundamental for the confirmation of doubtful clinical diagnoses, especially in the light of recently revised diagnostic criteria, and for the early identification of genotypes, albeit few, that correlate with specific phenotypes.

Head circumference and anthropometric changes and their relation to plexiform and skin neurofibromas in sporadic and familial neurofibromatosis 1 Brazilian adults: a cross-sectional study

BACKGROUND

Neurofibromatosis 1 (NF1) is a common autosomal dominant syndrome with complete penetrance and highly variable expressivity. The cutaneous neurofibroma (Cnf) and plexiform neurofibroma (Pnf), café-au-lait spots, and freckle-like lesions are common in NF1, but many other manifestations can occur. We aimed to evaluate head circumference, height, weight, body mass index (BMI), head circumference-to-height ratio (HCHR) and waist-hip ratio (WHR) in adult NF1 Brazilian individuals versus a paired control group and investigate their correlation with the presence of clinically visible Pnfs, and number of "skin neurofibromas" (Snf), which include both cutaneous and subcutaneous neurofibromas.

METHODS

A case-control study was conducted with 168 individuals, 84 with NF1 and 84 without NF1, paired by sex and age. Head circumference and anthropometric measurements, Snf quantification, evaluation of clinically visible Pnf and familial inheritance were accessed.

RESULTS

Prevalence of macrocephaly was significantly higher in NF1 women. Height and weight were significantly lower in both males and females with NF1. HCHR was higher in the NF1 group than in the control group for both sexes. BMI was significantly lower in men with NF1. Waist and hip circumferences were significantly reduced in NF compared with the controls, but the mean WHR was significantly lower only in NF1 women. No correlation was found between the Snf and head circumference and anthropometric measurements, sex or family history. The presence and larger size of clinically visible plexiform neurofibromas were associated with normal stature (p = 0.037 and p = 0.003, respectively).

CONCLUSIONS

NF1 individuals have increased prevalence of macrocephaly, short stature, low BMI, and reduced abdominal fat. There is no relation between head circumference and anthropometric data with family history, or neurofibromas.

Neurological manifestations of neurofibromatosis type 1: our experience

INTRODUCTION

Neurofibromatosis type 1 (NF1) is a progressive multisystem disorder following an autosomal dominant inheritance pattern that presents with multiple neurological manifestations.

METHODS

We reviewed medical histories of patients with NF1 followed up at our hospital's paediatric neurology department from May 1990 to 31 December 2018. We collected data on neurological symptoms.

RESULTS

A total of 128 patients with NF1 were identified. Mean age (SD) at NF1 diagnosis was 4.43 (3.38) years (range, 0.5-14.5 years). There was a slight female predominance (53.1%). Macrocephaly (head circumference over 2 SDs above average for age) was present in 37.5% of cases. Attention-deficit/hyperactivity disorder was recorded in 28.9% of patients (37): combined type in 20 patients, predominantly inattentive in 15, and predominantly impulsive/hyperactive in 2. Other manifestations included headache (18.6%), cognitive impairment (7.8%), motor deficit (6.2%), and epilepsy (4.68%). Brain MRI was performed in 85 patients, revealing T2-weighted hyperintensities in the basal ganglia and/or cerebellum in 60 patients (70.5%), Chiari malformation type 1 in 4 cases, and arachnoid cysts in 3. Optic nerve gliomas were identified by MRI in 22 patients (25.8%). Other MRI findings included plexiform neurofibromas (9.3%) and central nervous system gliomas (3.1%).

CONCLUSIONS

The neurological manifestations identified in our sample are consistent with those reported in the literature. Effective transfer strategies from paediatric neurology departments and subsequent clinical follow-up by adult neurology departments are needed to prevent loss to follow-up in adulthood.

Towards a Rational and Efficient Diagnostic Approach in Children Referred for Growth Failure to the General Paediatrician

Based on a recent Dutch national guideline, we propose a structured stepwise diagnostic approach for children with growth failure (short stature and/or growth faltering), aiming at high sensitivity for pathologic causes at acceptable specificity. The first step is a detailed clinical assessment, aiming at obtaining relevant clinical clues from the medical history (including family history), physical examination (emphasising head circumference, body proportions and dysmorphic features) and assessment of the growth curve. The second step consists of screening: a radiograph of the hand and wrist (for bone age and assessment of anatomical abnormalities suggestive for a skeletal dysplasia) and laboratory tests aiming at detecting disorders that can present as isolated short stature (anaemia, growth hormone deficiency, hypothyroidism, coeliac disease, renal failure, metabolic bone diseases, renal tubular acidosis, inflammatory bowel disease, Turner syndrome [TS]). We advise molecular array analysis rather than conventional karyotyping for short girls because this detects not only TS but also copy number variants and uniparental isodisomy, increasing diagnostic yield at a lower cost. Third, in case of diagnostic clues for primary growth disorders, further specific testing for candidate genes or a hypothesis-free approach is indicated; suspicion of a secondary growth disorder warrants adequate further targeted testing.

Neurofibromatosis type 1 of the child increases birth weight

Neurofibromatosis type 1 (NF1) is associated with reduced adult height, but there are no cohort studies on birth size. This retrospective study includes a cohort of 1,410 persons with NF1 and a matched comparison cohort from the general population. Figures for birth size were retrieved from the administrative registers of Finland, and the data were converted to standard deviation scores (SDS), defined as standard deviation difference to the reference population. The birth weight among infants with NF1 was higher than among infants without the disorder (adjusted mean difference [95% confidence interval]: 0.53 SDS [0.19–0.87]), as was the head circumference at birth (0.58 SDS [0.26–0.90]). The birth length of the NF1 infants did not differ significantly from the comparison cohort. The birth weight in the group consisting of NF1 and non‐NF1 infants of NF1 mothers was lower than among infants of mothers in the comparison cohort (−0.28 SDS [−0.51 to −0.06]), as was the birth length (−0.22 SDS [−0.45 to 0.00]). In conclusion, the birth weight and head circumference of persons with NF1 are significantly higher than those of persons without the disorder. NF1 of the mother reduces birth weight and birth length of the infant.

Macrocephaly Is Not a Predictor of Optic Pathway Glioma Development or Treatment in Neurofibromatosis Type 1

Neurofibromatosis type 1 is a common neurogenetic disorder characterized by significant clinical variability. As such, numerous studies have focused on identifying clinical, radiographic, or molecular biomarkers that predict the occurrence or progression of specific clinical features in individuals with neurofibromatosis type 1. One of these clinical biomarkers, macrocephaly, has been proposed as a prognostic factor for optic pathway glioma development. In the current study, the authors demonstrate that macrocephaly is not associated with the development of these brain tumors or the need to institute treatment for clinical progression. These findings suggest that macrocephaly is not a robust biomarker of optic pathway glioma formation or progression in children with neurofibromatosis type 1.

Endocrine implications of neurofibromatosis 1 in childhood

In 1882, von Recklinghausen described a group of patients with multiple tumors arising from the 'endoneurium' of peripheral nerves, and called them 'neurofibromas'. The term von Recklinghausen disease was used up to the end of the 20th century, when the gene of neurofibromatosis (NF1) was cloned on chromosome 17q11.2. The gene product is a cytoplasmic protein termed neurofibromin, regulating proliferation and maturation of both glial and neuronal progenitors during embryogenesis. Loss of neurofibromin function determines the hyperactivation of the proto-oncogene RAS, leading to an increased risk of tumor formation, predominantly affecting the skin, bone and the nervous system. NF1 is clinically and genetically distinct from neurofibromatosis type 2, characterized by bilateral vestibular schwannomas and other nervous system tumors. An increased incidence of central precocious puberty, diencephalic syndrome, GH deficiency and GH hypersecretion has been described in NF1 children. These conditions are commonly complications of optic pathway gliomas (OPG) involving the hypothalamic and sellar region. Nevertheless, these endocrine disorders have been observed also in children without evidence of OPG at magnetic resonance imaging. Clinical and laboratory follow-up is crucial in all children with NF1, particularly in those with an OPG, aiming at the early identification of signs suggestive of secondary endocrine alterations.

Diagnostic accuracy of referral criteria for head circumference to detect hydrocephalus in the first year of life

BACKGROUND

Increased head circumference is often the first and main sign leading to the diagnosis of hydrocephalus. Our aim is to investigate the diagnostic accuracy of referral criteria for head circumference to detect hydrocephalus in the first year of life.

METHODS

A reference group with longitudinal head circumference data (n = 1938) was obtained from the Social Medical Survey of Children Attending Child Health Clinics study. The case group comprised infants with hydrocephalus treated in a tertiary pediatric hospital who had not already been detected during pregnancy (n = 125). Head circumference data were available for 43 patients. Head circumference data were standardized according to gestational age-specific references.

RESULTS

Sensitivity and specificity of a very large head circumference (>2.5 standard deviations on the growth chart) were, respectively, 72.1% (95% confidence interval [CI]: 56.3-84.7) and 97.1% (95% CI:96.2-97.8). These figures were, respectively, 74.4% (95% CI: 58.8-86.5) and 93.0% (95% CI:91.8-94.1) for a large head circumference (>2.0 standard deviation), and 76.7% (95% CI:61.4-88.2) and 96.5% (95% CI:95.6-97.3) for a very large head circumference and/or a very large (>2.5 standard deviation) progressive growth of head circumference.

CONCLUSIONS

A very large head circumference and/or a very large progressive growth of head circumference shows the best diagnostic accuracy to detect hydrocephalus at an early stage. Gestational age-specific growth charts are recommended. Further improvements may be possible by taking into account parental head circumference.

Anthropometric characteristics and comorbidities in Japanese patients with neurofibromatosis type 1: a single institutional case-control study

Neurofibromatosis type 1 (NF1) is a well-known genetic disorder characterized by café-au-lait spots and neurofibromas, but many other clinical characteristics and associated comorbidities also have been reported. This study aimed to characterize NF1 further by investigating its association with anthropometric characteristics and other diseases. We performed a case-control study of 227 NF1 patients (101 male, 126 female) and a randomly selected age- and sex-matched control group of 681 non-NF1 patients (303 male, 378 female) who visited our institution in Japan. We examined adult (≥20 years) height and body mass index (BMI), and, in the total sample, allergic diseases (bronchial asthma [BA], atopic dermatitis [AD] and allergic rhinitis) and other respiratory cardiovascular and psychiatric disorders. In adults, the mean BMI was lower in the NF1 group than in the control group, and was significantly statistically different among men (P = 0.0238). In the whole sample, the prevalences of BA (P = 0.0184), AD (P = 0.0144) and valvular heart disease (P = 0.0166) were significantly greater in the NF1 group than in the control group. To date, no similar research on the BMI or the prevalence of allergic disease in NF1 patients has been reported. Our results suggest that NF1 patients tend to have lower BMI and may have alterations in specific metabolic pathways and altered allergic immunity.

Is there a relationship between executive functions and academic success in children with neurofibromatosis type 1?

The present study aimed to compare the executive function (EF) of children with neurofibromatosis type 1 (NF1) to those of typically developing children and to investigate whether those abilities could predict the child's academic success in terms of academic skills and enablers. Twenty-nine children with NF1 and 27 age-and-gender-matched controls (aged 8-16 years) were examined with two tests to measure EF in an ecologically valid manner: the Behavioural Assessment of the Dysexecutive Syndrome in Children (BADS-C) and the parent questionnaire for the Behavior Rating Inventory of Executive Function (BRIEF). In order to evaluate academic success we used the Academic Competence Evaluation Scales (ACES). The performance of the NF1 group was significantly lower on the Water and Key search subtest of the BADS-C and on four scales of the BRIEF: initiate; working memory; plan/organise and organisation of materials. Significant correlations and predictive models via regression analysis were generated for: BADS-C, BRIEF and ACES scores. Based on these findings, children with NF1 have executive dysfunction that partially accounts for their difficulties in academic achievements.