Nearly completely reversible brain abnormalities in a patient with incontinentia pigmenti

The Forgotten Phacomatoses: A Neuroimaging Review of Rare Neurocutaneous Disorders

Phakomatoses, or neurocutaneous syndromes, are a heterogeneous group of rare genetic disorders that predominantly affect structures arising from the embryonic ectoderm, namely the skin, eye globe, retina, tooth enamel, and central nervous system. Other organs are also involved in some syndromes, mainly cardiovascular, pulmonary, renal, and musculoskeletal systems. Currently, more than sixty distinct entities belonging to this category have been described in the literature. Common phakomatoses include conditions like Neurofibromatosis and Tuberous sclerosis. Several review papers have focused on various aspects of these common conditions, including clinical presentation, genetic and molecular basis, and neuroimaging features. In this review, we focus on rare neurocutaneous syndromes: Melanophakomatoses (Ie, Neurocutaneous Melanosis, and Incontinentia Pigmenti), Vascular Phakomatoses (Ie, Ataxia Telangiectasia and PHACE Syndrome), and other conditions such as Cowden Syndrome, Basal Nevus Syndrome, Schwannomatosis, Progressive Facial Hemiatrophy, Gomez-Lopez-Hernandez Syndrome, Wyburn-Mason Syndrome, CHILD Syndrome, and Proteus Syndrome. We also review the neuroradiologic manifestations of these conditions as a guide for neurologists and neuroradiologists in their daily practice.

The Rare Neurocutaneous Disorders: Update on Clinical, Molecular, and Neuroimaging Features

Phakomatoses, also known as neurocutaneous disorders, comprise a vast number of entities that predominantly affect structures originated from the ectoderm such as the central nervous system and the skin, but also the mesoderm, particularly the vascular system. Extensive literature exists about the most common phakomatoses, namely neurofibromatosis, tuberous sclerosis, von Hippel-Lindau and Sturge-Weber syndrome. However, recent developments in the understanding of the molecular underpinnings of less common phakomatoses have sparked interest in these disorders. In this article, we review the clinical features, current pathogenesis, and modern neuroimaging findings of melanophakomatoses, vascular phakomatoses, and other rare neurocutaneous syndromes that may also include tissue overgrowth or neoplastic predisposition.

Cerebral Arteriopathy in a Newborn With Incontinentia Pigmenti

BACKGROUND

Incontinentia pigmenti is a rare X-linked neurocutaneous disorder that can present in the neonatal period with seizures and encephalopathy. Brain magnetic resonance imaging and magnetic resonance angiography may reveal cerebral infarction and arteriopathy.

PATIENT DESCRIPTION

We describe a neonate with the typical rash of incontinentia pigmenti along with seizures and brain magnetic resonance imaging abnormalities.

RESULTS

Brain magnetic resonance imaging, magnetic resonance angiography, and magnetic resonance spectroscopy at age one week revealed chronic and acute brain injury, arteriopathy of the small and medium-sized cerebral vessels, and elevation of a lactate metabolite peak. By age six months, her magnetic resonance angiogram had normalized. At age 2.5 years, she has well-controlled complex partial seizures, global developmental delay, and residual hemiplegia.

CONCLUSION

Despite extensive cerebral arteriopathy in association with incontinentia pigmenti, this girl had a relatively stable early clinical course, steady developmental progress over time, and seizures that have been well controlled. Later brain imaging revealed resolution of the arteriopathy.

Neurocutaneous syndromes

Neurocutaneous syndromes (or phakomatoses) are a diverse group of congenital disorders that encompass abnormalities of neuroectodermal and, sometimes, mesodermal development, hence commonly involving the skin, eye, and central nervous system. These are often inherited conditions and typically present in early childhood or adolescence. Some of the abnormalities and clinical symptoms may, however, be progressive, and there is an increased risk of neoplastic formation in many of the syndromes. As a group, neurocutaneous syndromes are characterized by distinctive cutaneous stigmata and neurologic symptomology, the latter often representing the most devastating and debilitating features of these diseases. Many of these syndromes are markedly heterogeneous in nature as they affect many organ systems. Given the incurable nature of these conditions and the broad spectrum of pathologies they comprise, treatments vary on a case-by-case basis and tend to be palliative rather than curative. With the advances in molecular genetics, however, greater understanding of biologic functions of the gene products and the correlative phenotypic expression is being attained, and this knowledge may guide future therapeutic developments. This chapter focuses on the cutaneous and neurologic pathology with emphasis on neuroimaging of selective neurocutaneous syndromes, including tuberous sclerosis, Sturge-Weber syndrome, Klippel-Trenaunay syndrome, ataxia-telangiectasia, and incontinentia pigmenti.

Incontinentia pigmenti

Incontinentia pigmenti is a rare genodermatosis in which the skin involvement occurs in all patients. Additionally, other ectodermal tissues may be affected, such as the central nervous system, eyes, hair, nails and teeth. The disease has a X-linked dominant inheritance pattern and is usually lethal to male fetuses. The dermatological findings occur in four successive phases, following the lines of Blaschko: First phase - vesicles on an erythematous base; second phase - verrucous hyperkeratotic lesions; third phase - hyperchromic spots and fourth phase - hypochromic atrophic lesions.

Incontinentia pigmenti and hypomelanosis of Ito

Incontinentia pigmenti (IP) is a rare X-linked dominant neurocutaneous disorder affecting ectodermal tissue: skin, eyes, central nervous system, hair, nails, and teeth. It is usually lethal for males in utero. The involved gene is NEMO, an essential component of the nuclear factor-kappa B (NF-κB) signaling pathway. Skin lesions are highly diagnostic, occurring in neonates, with a particular distribution on Blaschko lines. The severity of the disease is related to ocular and neurological impairment. The hallmark of ocular IP is retinal vasculopathy including peripheral retinal vascular nonperfusion, macular infarction and neovascularization, and preretinal neovascularization. CNS involvement consists of seizures, mental retardation, hemiparesis, spasticity, microcephaly, cerebellar ataxia, and coma. It often occurs in neonates. Some patients have persistent pharmacoresistant seizures throughout life. MRI findings consist essentially in: white-matter lesions; scattered cortical neuronal necrosis; multiple cerebral infarctions; cerebral atrophy, hypoplasia of the corpus callosum, encephalomalacia and neuronal heterotopia. A predominant role of vascular occlusive phenomena in small vessels is highly suspected. In fact several intricate mechanisms could be discussed: vascular, inflammatory, developmental mechanisms. Their role and predictive factors of IP CNS involvement in neonatal IP need to be better understood to identify effective innovative therapies. Hypomelanosis of Ito can occur in the neonate, infancy, or childhood, be isolated or diffuse, often following the Blaschko lines, and can fade in childhood or adulthood. It is due to reduced melanin in the epidermis. Eye, central nervous (mental retardation, epilepsy, language disabilities, motor system dysfunction, psychiatric symptoms including autism - with frequent cortical malformations including hemimegalencephaly and white matter involvement), and musculoskeletal systems can also be affected. Mosaicism with various chromosomal rearrangements has been reported.