Type I neurofibromatosis: a geno-oculo-dermatologic update

Insights into Novel Choroidal and Retinal Clinical Signs in Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a rare inherited neurocutaneous disorder with a major impact on the skin, nervous system and eyes. The ocular diagnostic hallmarks of this disease include iris Lisch nodules, ocular and eyelid neurofibromas, eyelid café-au-lait spots and optic pathway gliomas (OPGs). In the last years, new manifestations have been identified in the ocular district in NF1 including choroidal abnormalities (CAs), hyperpigmented spots (HSs) and retinal vascular abnormalities (RVAs). Recent advances in multi-modality imaging in ophthalmology have allowed for the improved characterization of these clinical signs. Accordingly, CAs, easily detectable as bright patchy nodules on near-infrared imaging, have recently been added to the revised diagnostic criteria for NF1 due to their high specificity and sensitivity. Furthermore, subclinical alterations of the visual pathways, regardless of the presence of OPGs, have been recently described in NF1, with a primary role of neurofibromin in the myelination process. In this paper, we reviewed the latest progress in the understanding of choroidal and retinal abnormalities in NF1 patients. The clinical significance of the recently revised diagnostic criteria for NF1 is discussed along with new updates in molecular diagnosis. New insights into NF1-related neuro-ophthalmic manifestations are also provided based on electrophysiological and optical coherence tomography (OCT) studies.

Neurofibromatosis: an update of ophthalmic characteristics and applications of optical coherence tomography

Neurofibromatosis (NF) is a multisystem disorder and tumor predisposition syndrome caused by genetic mutation on chromosome 17-17q11.2 in NF type 1 (NF1), and on chromosome 22-22q12.2 in NF type 2. The disorder is characterized by considerable heterogeneity of clinical expression. NF1 is the form with the most characteristic ocular manifestations. Lisch nodules of the iris are among the well-known diagnostic criteria for the disease. Glaucoma and associated globe enlargement have been described in a significant proportion of patients with NF1 and orbital–facial involvement. Optic nerve glioma may cause strabismus and proptosis, and palpebral neurofibroma may reach considerable size and occasionally show malignant transformation. Near infrared reflectance has greatly contributed to enhancing our knowledge on choroidal alterations in NF1. Indeed, some authors have proposed to include these among the diagnostic criteria. Optical coherence tomography has given new insight on retinal alterations and is a noninvasive tool in the management of optic nerve gliomas in children. Ocular manifestations in NF type 2 can range from early-onset cataracts in up to 80% of cases to optic nerve hamartomas and combined pigment epithelial and retinal hamartomas.

Pigmentary disorders of the eyes and skin

Oculocutaneous albinism, Menkes syndrome, tuberous sclerosis, neurofibromatosis type 1, dyskeratosis congenita, lentiginosis profusa syndrome, incontinentia pigmenti, and Waardenburg syndrome all are genodermatoses that have well established gene mutations affecting multiple biological pathways, including melanin synthesis, copper transport, cellular proliferation, telomerase function, apoptosis, and melanocyte biology. Onchocerciasis results from a systemic inflammatory response to a nematode infection. Hypomelanosis of Ito is caused by chromosomal mosaicism, which underlies its phenotypic heterogeneity. Incomplete migration of melanocytes to the epidermis and other organs is the underlying feature of nevus of Ota. Vogt-Koyangi-Harada and vitiligo have an autoimmune etiology; the former is associated with considerable multiorgan involvement, while the latter is predominantly skin-limited.

Cutaneous and ocular manifestations of neurocutaneous syndromes

Neurocutaneous syndromes are a heterogeneous group of congenital and hereditary disorders with manifestations in the skin and the nervous system, usually together with ocular features that represent diagnostic clues and potential sources of morbidity. Dermatologists and ophthalmologists often need to work together in identifying and managing patients with these conditions; herein, we focus on classic and under-recognized neurocutaneous syndromes. We begin with autosomal dominant genodermatoses characterized by hamartomas and tumors in the skin, eyes, and central nervous system: neurofibromatosis type 1, tuberous sclerosis complex, and PTEN hamartoma-tumor syndrome. This is followed by a discussion of two mosaic disorders, Sturge-Weber syndrome and neurocutaneous melanocytosis. In addition to providing an update on clinical presentations and evaluation of patients with these conditions, we review recent insights into their pathogenesis, drawing attention to relationships among the diseases on a molecular level and implications regarding treatment. We also highlight the major features of other neurocutaneous syndromes that have ocular findings plus pigmentary, vascular, hyperkeratotic, adnexal, connective tissue, photosensitive, and inflammatory manifestations in the skin.

Ophthalmic manifestations of systemic diseases--part 1: phakomatoses, hematologic malignancies, metastases, and histiocytosis

The orbit can be secondarily involved in various systemic conditions. The ophthalmic involvement is often the first clue to the presence of an underlying systemic condition. The ophthalmic involvement in systemic diseases can be either ocular or extraocular. The extent of involvement can be well delineated by imaging modalities like computed tomography and magnetic resonance imaging. In the first part of the article, we provide an overview of systemic diseases affecting the orbit, briefly discuss the modalities for orbital imaging, and discuss the imaging appearances of ophthalmic involvement in (1) phakomatoses, (2) hematologic malignancies, (3) metastases, and (4) histiocytosis. At the end of the 2-part article, we discuss a pattern-based approach and differential diagnosis of orbital lesions in systemic diseases.

Increased prevalence of ametropia in children with neurofibromatosis type 1 disease

Neurofibromatosis type 1 disease is an autosomal dominant disorder associated with numerous ophthalmic and systemic manifestations. Organic causes of visual loss include optic pathway gliomas, orbital plexiform neurofibroma, and glaucoma. In this study, the authors analyzed the prevalence of ametropia as a cause for visual loss in children with neurofibromatosis type 1 disease younger than age 12 years compared to matched controls. Only children with normal neuroimaging were evaluated. Myopia, hyperopia, astigmatism, and anisometropia were all more common in children with neurofibromatosis type 1 disease; however, statistically significant differences were observed in mild myopia and astigmatism alone. A higher need for optical correction was found in children with neurofibromatosis type 1 disease (33.3% vs 17.1% of controls, P = .049). In conclusion, children with neurofibromatosis type 1 disease have a higher prevalence of ametropia, especially mild myopia and astigmatism, often requiring optical correction. Routine refraction screening is recommended for limiting preventable visual loss.

Anisometropia in children with neurofibromatosis type 1 and unilateral optic nerve glioma

BACKGROUND

Optic nerve glioma (ONG) occurs in 5% to 25% of individuals with neurofibromatosis type 1 (NF1). Recently an association between this lesion and unilateral myopia was reported in a series of 4 pediatric patients. The purpose of this study was to determine whether unilateral ONG is associated with an increased prevalence of anisometropia.

METHODS

The medical records of children <16 years of age with NF1 disease and unilateral ONG or normal neuroimaging examined at Tel-Aviv Medical Center between April 2008 and July 2013 were retrospectively reviewed to determine the prevalence of anisometropia and anisoastigmatism.

RESULTS

A total of 75 children with NF1 disease were included. Of these, 25 (11 boys) had a unilateral ONG (mean age, 7.2 years; range, 2-16 years) and 50 (29 boys) had normal neuroimaging (mean age, 8.3 years; range, 1-15 years). The mean refraction (spherical equivalent) of eyes with ONG did not differ significantly from that of the contralateral eyes (0.74 ± 1.41 D vs 0.71 ± 1.19 D; P = 0.935; 95% CI, -0.710 to 0.770); moreover, there was a high correlation between the refraction of eyes with ONG and contralateral eyes (r = 0.946, P < 0.001). The prevalence of anisometropia in children with ONG and in NF1 children with no orbital pathology did not differ significantly (8% vs 16%; P = 0.480), and the prevalence of anisoastigmatism was also similar in both groups (4% vs 14%, P = 0.255).

CONCLUSIONS

ONG in children with NF1 is not associated with increased prevalence of anisometropia.

Whole-genome copy number variation analysis in anophthalmia and microphthalmia

Anophthalmia/microphthalmia (A/M) represent severe developmental ocular malformations. Currently, mutations in known genes explain less than 40% of A/M cases. We performed whole-genome copy number variation analysis in 60 patients affected with isolated or syndromic A/M. Pathogenic deletions of 3q26 (SOX2) were identified in four independent patients with syndromic microphthalmia. Other variants of interest included regions with a known role in human disease (likely pathogenic) as well as novel rearrangements (uncertain significance). A 2.2-Mb duplication of 3q29 in a patient with non-syndromic anophthalmia and an 877-kb duplication of 11p13 (PAX6) and a 1.4-Mb deletion of 17q11.2 (NF1) in two independent probands with syndromic microphthalmia and other ocular defects were identified; while ocular anomalies have been previously associated with 3q29 duplications, PAX6 duplications, and NF1 mutations in some cases, the ocular phenotypes observed here are more severe than previously reported. Three novel regions of possible interest included a 2q14.2 duplication which cosegregated with microphthalmia/microcornea and congenital cataracts in one family, and 2q21 and 15q26 duplications in two additional cases; each of these regions contains genes that are active during vertebrate ocular development. Overall, this study identified causative copy number mutations and regions with a possible role in ocular disease in 17% of A/M cases.