Discordance for Schimmelpenning-Feuerstein-Mims syndrome in monochorionic twins supports the concept of a postzygotic mutation

Autopsy case of linear nevus sebaceous syndrome with KRAS (G12D) mutation

Linear nevus sebaceous syndrome (LNSS) is a neurocutaneous syndrome associated with systemic complications that involve multiple organs, including the skin, central nervous system, eyes, and skeleton. LNSS is considered to be caused by mosaic RAS gene mutation. In this report, we present an autopsy case of LNSS in a Japanese boy. The affected neonate had hydrops fetalis and was born at 28 weeks and 4 days of gestation, weighing 2104 g. He had bilateral inverted eyelids, verrucous linear nevus separated along Blaschko's line, myocardial hypertrophy, and pharyngeal constriction, and underwent intensive treatment in NICU for arrhythmia, hydrocephalus, and respiratory distress. The hydrocephalus progressed gradually and he died at the age of 181 days, 12 days after a sudden cardiac arrest and recovery. KRAS G12D mutation was found in a skin biopsy specimen but not in blood cells, suggesting a postzygotic mosaicism. Autopsy revealed novel pathological findings related to LNSS, including intracranial lipomatous hamartoma and mesenteric lymphangioma, in addition to previously reported findings such as multicystic dysplastic kidney. There was the limited expression of mutated KRAS protein in kidneys.

Genodermatoses associated with melanocytic nevi

Though melanocytic nevi are ubiquitous in the general population, they can also be key cutaneous manifestations of genetic syndromes. We describe genodermatoses associated with melanocytic nevi and discuss their clinical characteristics, cutaneous manifestations, underlying genetics, and, if applicable, guidelines for when genetic testing should be performed. We categorized these genodermatoses based on their association with congenital nevi, acquired nevi, or nevi whose first appearance is unknown. In many cases, the distinctive morphology or distribution of melanocytic nevi can be an important clue that an underlying genetic syndrome is present, allowing both the patient as well as family members to be screened for the more serious complications of their genetic disorder and receive education on potential preventative measures. As we continue to advance our understanding of how various genotypes give rise to the wide spectrum of phenotypes observed in these genodermatoses, we shall be able to better stratify risk and tailor our screening methods to clinically manage the heterogeneous manifestations of genodermatoses among these patients.

Linear Nevus Sebaceous Syndrome in a Child With Infantile Spasms and Focal Cortical Dysplasia

Linear nevus sebaceous syndrome (LNSS) is a rare neurocutaneous syndrome with important neurological involvement including brain malformation, focal seizures, and developmental delay. We discuss a case with a unique presentation with localization-related infantile spasms and review the clinical and radiological features of this case. To our knowledge, there are no previously reported cases of LNSS with infantile spasms and cortical dysplasia. Therefore, the presented case will make an important contribution to the available knowledge.

Inguinal lymph nodes agenesia in a patient with Schimmelpenning-Feuerstein-Mims syndrome with proven somatic KRAS mutation

Schimmelpenning-Feuerstein-Mims (SFM) syndrome is a neurocutaneous disorder that can affect many body systems. The principal and most characteristic anomalies are craniofacial naevus sebaceous in association with neurological, ocular and skeletal findings. The presence of vascular malformations in this condition is unusual; nevertheless, vascular malformations have been suggested by many authors to be part of the spectrum of the same disease. Few cases have been published on the association of SFM with lymphatic malformations. This syndrome is categorized as a mosaic RASopathy due to postzygotic mutations in the HRAS, KRAS or NRAS genes. These genes are involved in the RAF-MEK-ERK signalling pathway, which is activated by mutant cells, increasing cellular proliferation. These mutations have been found only in naevus sebaceous cells, and may be also the explanation for many of the associated pathologies. We report a case of an 18-year-old boy diagnosed with SFM syndrome associated with lymphatic malformation in the legs and agenesia of the inguinal lymph nodes. The lymphatic alterations were diagnosed by gammography of the legs. The genetic diagnosis was confirmed by the presence of a KRAS postzygotic mutation in naevus sebaceous cells of a skin specimen. Genetically confirmed cases of mosaic RASopathies should be used to more accurately characterize phenotypic presentations of this syndrome and develop a future therapeutic strategy, such as molecular targeted therapy.

Pathogenic postzygotic mosaicism in the tyrosine receptor kinase pathway: potential unidentified human disease hidden away in a few cells

Mutations occurring during embryonic development affect only a subset of cells resulting in two or more distinct cell populations that are present at different levels, also known as postzygotic mosaicism (PZM). Although PZM is a common biological phenomenon, it is often overlooked as a source of disease due to the challenges associated with its detection and characterization, especially for very low-frequency variants. Moreover, PZM can cause a different phenotype compared to constitutional mutations. Especially, lethal mutations in receptor tyrosine kinase (RTK) pathway genes, which exist only in a mosaic state, can have completely new clinical manifestations and can look very different from the associated monogenic disorder. However, some key questions are still not addressed, such as the level of mosaicism resulting in a pathogenic phenotype and how the clinical outcome changes with the development and age. Addressing these questions is not trivial as we require methods with the sensitivity to capture some of these variants hidden away in very few cells. Recent ultra-accurate deep-sequencing approaches can now identify these low-level mosaics and will be central to understand systemic and local effects of mosaicism in the RTK pathway. The main focus of this review is to highlight the importance of low-level mosaics and the need to include their detection in studies of genomic variation associated with disease.

Identification of KRAS mutation in a patient with linear nevus sebaceous syndrome: a case report

Background

Linear nevus sebaceous syndrome (LNSS) is a rare genetic disease characterized by large linear sebaceous nevus typically on the face, scalp, or neck. LNSS could be accompanied by multisystem disorders including the central nervous system. Herein, we report gene mutational profile via whole exome sequencing of both lesional and non-lesional skin samples in a LNSS patient.

Case presentation

A 17-year-old girl presented with multisystem abnormalities, including large skin lesions, ocular disorders, abnormal bone development and neurological symptoms. A diagnosis of LNSS was established based on clinical manifestations, histopathological and imaging findings. The skin lesions were resected and no recurrence was noted at the time of drafting this report. Whole exome sequencing of genomic DNA revealed the following 3 mutations in the lesions of the index patient: KRAS (c.35G > A, p.G12D), PRKRIR (c.A1674T, p.R558S), and RRP7A (c. C670T, p.R224W), but no mutation was found in the healthy skin and peripheral blood sample of the index patient, or in the blood samples of her parents and sibling. PCR-mediated Sanger sequencing of DNA derived from lesional skin sample of the index patient verified KRAS mutation, but not PRKRIR (c.A1674T, p.R558S) and RRP7A (c. C670T, p.R224W). None of the 3 mutations was found in Sanger sequencing in skin lesions of 60 other cases of nevus sebaceous patients.

Conclusions

Our findings show the relevance of KRAS mutation to LNSS, providing new clues in understanding related genetic heterogeneity which could aid genetic counselling for LNSS patients.

Association of Central Precocious Puberty with a Rare Presentation of Schimmelpenning-Feuerstein-Mims Syndrome in a Peruvian Girl

Schimmelpenning–Feuerstein–Mims syndrome (SFM), an epidermal nevus syndrome characterized by skin lesions, has an estimated incidence of 1 per 10 000 live births. Nevus sebaceous, the most common cutaneous lesion, and verrucous nevus, the less frequent lesion, are coupled with a wide range of extracutaneous manifestations. As part of these manifestations, rarely, central precocious puberty can arise. We report the case of a 1-year-5-month-old girl who presented to the Endocrinology and Metabolism Department with breast enlargement that began at one year of age, growth of pubic and axillary hair three months later, and vaginal bleeding that occurred five months later. During clinical examination, melanocytic nevi, with a diameter ranging from 3 to 5 mm, were noted on the face. Verrucous nevi of variable size with a tendency for coalescence following the lines of Blaschko and melanocytic nevi with a diameter ranging from 3 to 6 mm were observed on the right hemibody and on the left hemibody, respectively. Right asymmetry of the lower extremities was observed. Laboratory findings showed a significant increase in the levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) after the gonadotropin-releasing hormone (GnRH) stimulation test; additionally, imaging demonstrated advanced bone age and pubertal changes in the internal genitals. Analyses of the H-RAS, K-RAS, and N-RAS genes in the blood and in the skin were performed, and a missense mutation in exon 2 of the gene, H-RAS c37G > C (p.G13R), was detected in the latter. Treatment with triptorelin, a GnRH analog, was initiated, and it gave good clinical response. Epidermal nevus syndrome has a wide and variable systemic involvement. Thus, it is important to consider the development of precocious puberty for a prompt diagnosis and to strategize a multidisciplinary approach from the beginning.

Do you know this syndrome? Schimmelpenning-Feuerstein-Mims syndrome

Nevus sebaceous is the most common type of organoid epidermal nevus, often located on the face, following the Blaschko's lines and with alterations in the ipsilateral central nervous system. Distinct disorders can be distinguished by the type of association with epidermal nevus. Schimmelpenning-Feuerstein-Mims syndrome is a rare multisystem disorder characterized by sebaceous nevus associated with extracutaneous abnormalities affecting the brain, eyes and bones. We report the case of an 8-year-old female patient with a yellowish verrucous plaque on the left temporal area extending ipsilaterally to the cervical region, combined with cicatricial alopecia, periocular nodule, and epibulbar tumors.

Concurrent somatic KRAS mutation and germline 10q22.3-q23.2 deletion in a patient with juvenile myelomonocytic leukemia, developmental delay, and multiple malformations: a case report

Background

The proto-oncogene KRAS performs an essential function in normal tissue signaling, and the mutation of KRAS gene is a key step in the development of many cancers. Somatic KRAS mutations are often detected in patients with solid and non-solid tumors, whereas germline KRAS mutations are implicated in patients with the Noonan syndrome, cardio-facio-cutaneous (CFC) syndrome and Costello syndrome. The deletion of chromosome 10q22.3-q23.2 is a rare cytogenetic abnormality, which often leads to distinct facial appearance and delays in speech and global development.

Case presentation

Herein, we report the case of a 4-year-old boy diagnosed with juvenile myelomonocytic leukemia. The boy also had syndromic features, such as speech and motor developmental delay, multiple congenital malformations, including distinct facial features, club feet, and cryptorchidism. Using whole-exome sequencing, we identified a pathogenic mutation in KRAS [c.34G > A, p.Gly12Ser] isolated from peripheral blood DNA. Sanger sequencing confirmed the wild-type sequence in the parents and patient’s salivary cell DNA indicating its somatic state. A 7311-kb deletion in 10q22.3-q23.2 was also revealed by chromosomal microarray analysis, which was later proved as a germline de novo variant.

Conclusion

Juvenile myelomonocytic leukemia in the patient was attributed to a somatic KRAS mutation, whereas the syndromic features of the patient were considered a consequence of germline chromosome 10q22.3-q23.2 deletion. Genetic testing for patients with complicated phenotypes can be valuable in detecting multiple pathogenic variants.

Clinical delineation of a subtype of frontonasal dysplasia with creased nasal ridge and upper limb anomalies: Report of six unrelated patients

Frontonasal dysplasias are rare congenital malformations of frontonasal process-derived structures, characterized by median cleft, nasal anomalies, widely spaced eyes, and cranium bifidum occultum. Several entities of syndromic frontonasal dysplasia have been described, among which, to date, only a few have identified molecular bases. We clinically ascertained a cohort of 124 individuals referred for frontonasal dysplasia. We identified six individuals with a similar phenotype, including one discordant monozygous twin. Facial features were remarkable by nasal deformity with creased ridge and depressed or absent tip, widely spaced eyes, almond-shaped palpebral fissures, and downturned corners of the mouth. All had apparently normal psychomotor development. In addition, upper limb anomalies, frontonasal encephalocele, corpus callosum agenesis, choanal atresia, and congenital heart defect were observed. We identified five reports in the literature of patients presenting with the same phenotype. Exome sequencing was performed on DNA extracted from blood of two individuals, no candidate gene was identified. In conclusion, we report six novel simplex individuals presenting with a specific frontonasal dysplasia entity associating recognizable facial features, limb and visceral malformations, and apparently normal development. The identification of discordant monozygotic twins supports the hypothesis of a mosaic disorder. Although previous patients have been reported, this is the first series, allowing delineation of a clinical subtype of frontonasal dysplasia, paving the way toward the identification of its molecular etiology.

Somatic KRAS mutation in an infant with linear nevus sebaceous syndrome associated with lymphatic malformations: A case report and literature review

RATIONALE

Linear nevus sebaceous syndrome (LNSS) is a rare neurocutaneous syndrome, characterized by nevus sebaceous,central nervous system (CNS), ocular and skeletal abnormalities. The present study describes KRAS somatic mosaic mutation in a case of LNSS with lymphatic malformations (LMs).

PATIENT CONCERNS

A 4-month-old female with a clinical diagnosis of LNSS presented with infantile spasms, mental retardation, skull dysplasia, ocular abnormalities, congenital atrial septal defect, and LMs.

DIAGNOSIS

Cervical ultrasonography revealed a 4.6 × 4.6 × 2.2cm no echo packet with clear boundary in the subcutaneous tissues of the right neck. The neck MRI indicated a cyst in the subcutaneous tissues of the right neck. Whole-exome sequencing revealed a low-level heterozygous mutation of the KRAS gene (c.35C > T; p.G12D, 19%) in the skin lesion sample. This mutation was not present in the blood samples of the patient and her parents.

INTERVENTIONS

The patient received sclerotherapy with paicibanil (OK-432) injection for the cyst.

OUTCOMES

Following 1 year of treatment, the patient exhibited fewer seizures. The mental and motor development was significantly improved. The patient can currently walk with assistance and speak simple words.

LESSONS

LNSS is a rare, congenital neurocutaneous syndrome consisting of a spectrum of abnormalities involving the skin, central nervous system, eyes, LMs and other systems. LNSS can be caused by postzygotic somatic mutation in the RAS family of genes. Multidisciplinary evaluation and treatment is needed.

Nevus Sebaceous and Its Association With Neurologic Involvement

Several terms are widely used to define cutaneous lesions affecting the epidermis in association with extracutaneous lesions. Recently, based on the wide spectrum of cutaneous epidermal lesions, the various underlying molecular mechanisms and patterns of associated features have led to improved definitions of these disorders. Nevus sebaceous syndrome has been placed under the umbrella term of epidermal nevus syndrome, in which the nevus sebaceous, a congenital hamartomatous lesion of the epidermis, is associated with anomalies involving the brain, eyes, and bones. Nevus sebaceous and neurologic manifestations were evaluated particularly based on their degree of intellectual delay, seizure type, treatment response, and electroencephalography and neuroradiological findings. A review of the literature in this topic is reported.

Therapeutic effects of CO2 laser therapy of linear nevus sebaceous in the course of the Schimmelpenning-Feuerstein-Mims syndrome

The Schimmelpenning-Feuerstein-Mims (SFM) syndrome is a rare phakomatosis which comprises a nevus sebaceous of Jadassohn, seizures and developmental delay associated with a wide spectrum of extracutaneous abnormalities including neurological, skeletal, ocular, cardiovascular and urogenital defects. We are presenting a case of an 18-year-old patient with systemic features of the SFM syndrome and an extensive linear nevus sebaceous partially removed with a carbon dioxide (CO2) laser. The treatment options of skin lesions in patients with SFM are discussed.

A protein domain-centric approach for the comparative analysis of human and yeast phenotypically relevant mutations

Background

The body of disease mutations with known phenotypic relevance continues to increase and is expected to do so even faster with the advent of new experimental techniques such as whole-genome sequencing coupled with disease association studies. However, genomic association studies are limited by the molecular complexity of the phenotype being studied and the population size needed to have adequate statistical power. One way to circumvent this problem, which is critical for the study of rare diseases, is to study the molecular patterns emerging from functional studies of existing disease mutations. Current gene-centric analyses to study mutations in coding regions are limited by their inability to account for the functional modularity of the protein. Previous studies of the functional patterns of known human disease mutations have shown a significant tendency to cluster at protein domain positions, namely position-based domain hotspots of disease mutations. However, the limited number of known disease mutations remains the main factor hindering the advancement of mutation studies at a functional level. In this paper, we address this problem by incorporating mutations known to be disruptive of phenotypes in other species. Focusing on two evolutionarily distant organisms, human and yeast, we describe the first inter-species analysis of mutations of phenotypic relevance at the protein domain level.

Results

The results of this analysis reveal that phenotypic mutations from yeast cluster at specific positions on protein domains, a characteristic previously revealed to be displayed by human disease mutations. We found over one hundred domain hotspots in yeast with approximately 50% in the exact same domain position as known human disease mutations.

Conclusions

We describe an analysis using protein domains as a framework for transferring functional information by studying domain hotspots in human and yeast and relating phenotypic changes in yeast to diseases in human. This first-of-a-kind study of phenotypically relevant yeast mutations in relation to human disease mutations demonstrates the utility of a multi-species analysis for advancing the understanding of the relationship between genetic mutations and phenotypic changes at the organismal level.

Mosaic RASopathies

"RASopathies" are a group of developmental syndromes with partly overlapping clinical symptoms that are caused by germline mutations of genes within the Ras/MAPK signaling pathway. Mutations affecting this pathway can also occur in a mosaic state, resulting in congenital syndromes often distinct from those generated by the corresponding germline mutations. For syndromes caused by mosaic mutations of the Ras/MAPK signaling pathway, the term "mosaic RASopathies" has been proposed. In the following article, genetic and phenotypic aspects of mosaic RASopathies will be discussed.

Monozygotic twin discordance for phacomatosis cesioflammea further supports the post-zygotic mutation hypothesis

Phacomatosis pigmentovascularis (PPV) is a group of sporadic skin disorders combining widespread cutaneous capillary malformations and pigmented nevi. Etiopathogenesis of the various forms of PPV is unknown, although a non-allelic twin spotting has been proposed as the most likely underlying mechanism. We report on the second instance of monozygotic twin discordance for PPV. Identical twins were observed shortly after birth, one affected by PPV and the other healthy, except for a standard Mongolian spot. Membrane examination was compatible with a monochorionic diamniotic pregnancy, and microsatellite analysis demonstrated monozygosity. This report confirms that PPV likely originates from a post-zygotic mutation rising shortly after conception and affecting different cell lineages. Speculations about mechanisms linked to phenotypic discrepancies among identical twins were also put forward.