Severe neuroimaging anomalies are usually associated with random X inactivation in leucocytes circulating DNA in X-linked dominant Incontinentia Pigmenti

An efficient molecular genetic testing strategy for incontinentia pigmenti based on single-tube long fragment read sequencing

Incontinentia pigmenti (IP) is a rare X-linked dominant neuroectodermal dysplasia that primarily affects females. The only known causative gene is IKBKG, and the most common genetic cause is the recurrent IKBKG△4-10 deletion resulting from recombination between two MER67B repeats. Detection of variants in IKBKG is challenging due to the presence of a highly homologous non-pathogenic pseudogene IKBKGP1. In this study, we successfully identified four pathogenic variants in four IP patients using a strategy based on single-tube long fragment read (stLFR) sequencing with a specialized analysis pipeline. Three frameshift variants (c.519-3_519dupCAGG, c.1167dupC, and c.700dupT) were identified and subsequently validated by Sanger sequencing. Notably, c.519-3_519dupCAGG was found in both IKBKG and IKBKGP1, whereas the other two variants were only detected in the functional gene. The IKBKG△4-10 deletion was identified and confirmed in one patient. These results demonstrate that the proposed strategy can identify potential pathogenic variants and distinguish whether they are derived from IKBKG or its pseudogene. Thus, this strategy can be an efficient genetic testing method for IKBKG. By providing a comprehensive understanding of the whole genome, it may also enable the exploration of other genes potentially associated with IP. Furthermore, the strategy may also provide insights into other diseases with detection challenges due to pseudogenes.

The Impact of the IKBKG Gene on the Appearance of the Corpus Callosum Abnormalities in Incontinentia Pigmenti

Incontinentia pigmenti (IP) is a rare skin disease combined with anomalies of the teeth, eyes, and central nervous system (CNS). Mutations of the IKBKG gene are responsible for IP. Among the most frequent CNS abnormalities found in IP using magnetic resonance imaging (MRI) are corpus callosum (CC) abnormalities. The aim of the study was to determine the presence of CC abnormalities, their relationship with the IKBKG mutations, and the possible presence of mutations of other genes. A group of seven IP patients was examined. Analyses of the IKBKG gene and the X-chromosome inactivation pattern were performed, as well as MRI and whole exome sequencing (WES) with the focus on the genes relevant for neurodegeneration. WES analysis showed IKBKG mutation in all examined patients. A patient who had a mutation of a gene other than IKBKG was excluded from further study. Four of the seven patients had clinically diagnosed CNS anomalies; two out of four had MRI-diagnosed CC anomalies. The simultaneous presence of IKBKG mutation and CC abnormalities and the absence of other mutations indicate that IKBKG may be the cause of CC abnormalities and should be included in the list of genes responsible for CC abnormalities.

Uncovering incontinentia pigmenti: From DNA sequence to pathophysiology

Incontinentia pigmenti (IP) is an X-linked dominant genodermatosis. The disease is known to be caused by recurrent deletion of exons 4-10 of the Inhibitor Of Nuclear Factor Kappa B Kinase Regulatory Subunit Gamma (IKBKG) gene located at the Xq28 chromosomal region, which encodes for NEMO/IKKgamma, a regulatory protein involved in the nuclear factor kappa B (NF-κB) signaling pathway. NF-κB plays a prominent role in the modulation of cellular proliferation, apoptosis, and inflammation. IKBKG mutation that results in a loss-of-function or dysregulated NF-κB pathway contributes to the pathophysiology of IP. Aside from typical skin characteristics such as blistering rash and wart-like skin growth presented in IP patients, other clinical manifestations like central nervous system (CNS) and ocular anomalies have also been detected. To date, the clinical genotype-phenotype correlation remains unclear due to its highly variable phenotypic expressivity. Thus, genetic findings remain an essential tool in diagnosing IP, and understanding its genetic profile allows a greater possibility for personalized treatment. IP is slowly and gradually gaining attention in research, but there is much that remains to be understood. This review highlights the progress that has been made in IP including the different types of mutations detected in various populations, current diagnostic strategies, IKBKG pathophysiology, genotype-phenotype correlation, and treatment strategies, which provide insights into understanding this rare mendelian disorder.

Challenges in Rare Diseases Diagnostics: Incontinentia Pigmenti with Heterozygous GBA Mutation

Rare diseases represent a diagnostic challenge due to their number, variety of clinical phenomena, and possibility of a simultaneous presence of two or more diseases. An illustration of this challenge is an occurrence of a late diagnosis of a proband initially diagnosed with West syndrome, later revealed to be caused by Incontinentia pigmenti (IP). Furthermore, 20 years later, it was discovered that the proband was also a carrier of a heterozygous GBA gene mutation. The methods used in diagnostics were as follows: IKBKG gene analysis, the X-chromosome inactivation assay, analyses of the genes relevant for neurodegeneration, WES analysis, analysis of biochemical parameters typical for Gaucher disease (GD), and autoantibodies including IFN-α2a and IFN-ω. To avoid overlooking IP and other possible rare disease diagnoses, carefully searching for dermatological signs in these conditions is recommended. It is important that the diagnostic criteria are based on quality and extensive data from multiple studies of each rare disease. Establishing precise diagnostic criteria for as many rare diseases as possible and establishing a publicly accessible database of rare diseases with a search possibility according to phenotypic abnormalities and genetic mutations would greatly facilitate and speed up the establishment of an accurate diagnosis.

Multidisciplinary consensus recommendations from a European network for the diagnosis and practical management of patients with incontinentia pigmenti

BACKGROUND

Incontinentia pigmenti (IP) is a rare multisystemic X-linked dominant genetic disorder characterized by highly diagnostic skin lesions. The disease can be misdiagnosed in infants, and complications affecting the eyes and/or the brain can be severe. Our objective was to highlight the urgency of an appropriate diagnosis and management strategy, as soon as the first symptoms appear, and the need for a well-codified monitoring strategy for each child.

METHODS

An in-depth literature review using a large number of databases was conducted. The selection criteria for articles were literature review articles on the disease, case series and retrospective studies based on the disease, clinical studies (randomized or not) on treatment, articles discussing patient care and management (treatment, diagnosis, care pathways), and recommendations. The research period was from 2000 until 2018. A group of multidisciplinary experts in IP management was involved, issued from different healthcare providers of the European Network for Rare Skin Diseases (ERN-Skin). The final recommendations have been submitted to two patient representative associations and to a general practitioner and a neonatal specialist prior to their finalization.

RESULTS AND CONCLUSION

The diagnosis of IP must be promptly performed to detect potential extracutaneous manifestations, thus allowing the timely implementation of specific therapeutic and monitoring strategies. Eye involvement can be a therapeutic urgency, and central nervous system (CNS) involvement requires a very rigorous long-term follow-up. Assessments and patient support should take into account the possible co-occurrence of various symptoms (including motor, visual and cognitive symptoms).

Importance of extracutaneous organ involvement in determining the clinical severity and prognosis of incontinentia pigmenti caused by mutations in the IKBKG gene

Incontinentia pigmenti (IP) is a rare X-linked skin disease caused by mutations in the IKBKG gene, which is required for activation of the nuclear factor-kappa B signalling pathway. Multiple systems can be affected with highly variable phenotypic expressivity. We aimed to clarify the clinical characteristics observed in molecularly confirmed Korean IP patients. The medical records of 25 females confirmed as IP by molecular genetic analysis were retrospectively reviewed. The phenotypic score of extracutaneous manifestations was calculated to assess the disease severity. The IKBKG gene partial deletion or intragenic mutations were investigated using long-range PCR, multiplex ligation-dependent probe amplification and direct sequencing methods. Among the 25 individuals, 18 (72%) were sporadic cases. All patients showed typical skin manifestations at birth or during the neonatal period. Extracutaneous findings were noted in 17 (68%) patients; ocular manifestations (28%), neurological abnormalities (28%), hair abnormalities (20%), dental anomalies (12%), nail dystrophy (8%). The common exon 4-10 IKBKG deletion was observed in 20 (80%) patients. In addition, five intragenic sequence variants were identified, including three novel variants. The phenotype scores were highly variable, ranging from abnormal skin pigmentation only to one or more extracutaneous features, although no significant difference was observed for each clinical characteristic between the group with sequence variants and that with common large deletion. Our cohort with IP showed heterogeneity of extracutaneous manifestations and high incidence of sporadic cases. Long-term monitoring with multidisciplinary management is essential for evaluating the clinical status, providing adequate genetic counselling and understanding the genotype-phenotype correlation in IP.

Incontinentia Pigmenti Associated with Aplasia Cutis Congenita in a Newborn Male with Klinefelter Syndrome: Is the Severity of Neurological Involvement Linked to Skin Manifestations?

We report a rare case of a newborn male affected by incontinentia pigmenti, Klinefelter syndrome, and aplasia cutis congenita, who developed severe cutaneous, neurological, and ophthalmological manifestations. Genetic analysis showed the presence of the common mutation of NEMO (exon 4–10 deletion), Klinefelter syndrome karyotype (47 XXY), and random X inactivation. This is in accordance with the severity of involvement of the affected tissues (skin, central nervous system, and retina). Indeed, the patient developed typical skin lesions all over the body, except the head. Equally, multiple lesions diffusely involving both the cortical grey matter and subcortical white matter of the cerebellum and cerebral hemispheres were observed. Discussing current knowledge about the etiopathogenesis of skin and brain lesions in incontinentia pigmenti, our case seems to support the proapoptotic origin of central nervous system involvement. Possibly, incontinentia pigmenti patients suffer an impaired protection against apoptosis at the level of cerebral endothelial cells of small vessels, leading to vascular damage and subsequent ischemic brain lesions.

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.

Unilateral Cerebral Atrophy: Severe Neuroimaging Feature of Incontinentia Pigmenti without Acute Encephalopathic State

Incontinentia pigmenti (IP) is a rare X-linked multisystem disease caused because of mutation in the IKBKG (inhibitor of kappa-B kinase gamma, previously NEMO) gene. Involvement of central nervous system is seen in approximately one-third of these patients. Ischemic strokes, symptomatic seizures, and encephalopathy can be seen during neonatal or early infancy age group. Typically, early bilateral brain involvement is seen with periventricular white matter injury, hemorrhagic infarction, and multifocal cortical injury. We reported a patient who did not have early encephalopathic presentation, but presented with right hemiparesis and intellectual impairment. Magnetic resonance imaging of the brain revealed extensive left cerebral white matter volume loss and encephalomalacia with Wallerian degeneration of the left cortical spinal tract. This case highlights a rare presentation of unilateral cerebral atrophy with no definite episode of acute encephalopathy during infancy to suggest pure intrauterine injury. Microvascular occlusion, inflammatory cerebral vasculopathy, and recurrent silent strokes possibly produced this extensive neurologic manifestation antenatally. We also reviewed the complex pathogenic mechanisms involved in IP.