Segmental hypomelanosis and hypermelanosis arranged in a checkerboard pattern are distinct naevi: flag-like hypomelanotic naevus and flag-like hypermelanotic naevus

GNAQ/GNA11-Related Benign and Malignant Entities-A Common Histoembriologic Origin or a Tissue-Dependent Coincidence

Uveal melanoma (UM), recognized as the most prevalent primary intraocular malignancy in adults, is primarily driven by mutations in the GNAQ and GNA11 genes. These genetic alterations are also implicated in other conditions, which exhibit distinct morphological characteristics. In this article, we investigate the role of GNAQ and GNA11 mutations across varied disorders (e.g., UM, skin blue nevi, and hemangiomas), emphasizing the shared pathogenic mechanisms that connect them despite their differing clinical manifestations. By investigating the molecular pathways affected by these mutations, we provide insights into the potential for targeted therapies that could address not only UM but also other disorders associated with GNAQ/GNA11 mutations. Moreover, we discuss the role of SOX10-positive perivascular cells that may be implicated in the complex pathophysiology of GNAQ/GNA11-related entities. Understanding the common molecular foundation of these conditions opens new ways for research and treatment opportunities, potentially leading to more effective, personalized therapeutic strategies.

Phacomatosis spilosebacea: A new name for a distinctive binary genodermatosis

Phacomatosis pigmentokeratotica (PPK) is defined by the association of papular nevus spilus arranged in a flag-like pattern and sebaceous nevus following Blaschko's lines. A systematic search of the worldwide literature retrieved 95 well-established PPK cases. An additional 30 cases were excluded for a number of reasons. Based on this study, we propose to rename PPK phacomatosis spilosebacea (PSS). Mosaic mutations of the HRAS gene are the only proven cause of PSS. The extracutaneous abnormalities of PSS result from various degrees of intermingling of Schimmelpenning syndrome and papular nevus spilus syndrome. PSS seems to be a condition at particularly high risk of developing basal cell carcinoma, urogenital malignancies, and vitamin D-resistant hypophosphatemic rickets. Extracutaneous abnormalities were detected in approximately 75% of PSS cases.

The Diagnostic Value of Congenital and Nevoid Cutaneous Lesions Associated with Autism Spectrum Disorders in Indian Children- A Case-Control Study

Background and Aims:

Cutaneous lesions are the defining features of several neurocutaneous syndromes like neurofibromatosis1(NF1), tuberous sclerosis complex (TSC), and Sturge Weber syndrome to name a few. With this background, we explored the possibility of identifying congenital and nevoid cutaneous markers that may help in the early recognition of autism spectrum disorders (ASD) in Indian children. The objective of this study was to measure the strength of association between congenital and nevoid cutaneous lesions and ASD among Indian children.

Methods:

A case-control study was conducted from January 2018 to June 2018. 132 children (18 months-16 years of age) with ASD and equal number of age and sex-matched children without autism were studied. Diagnosis of ASD was based on DSM-5 criteria. All the children were examined for cutaneous lesions with special attention to nevoid and congenital conditions. The strength of association was measured using the diagnostic odds ratio (OR).

Results:

The prevalence of congenital and nevoid lesions were higher in ASD group (OR = 3.12, P = 0.0001). Among them, pigmentary mosaicism of hyperpigmented type (OR = 2.76, P = 0.02) and café-au-lait macules (CALMs) (OR = 2.40, P = 0.001) were the most prevalent with hyperpigmented pigmentary mosaicism showing a higher association with autism. Atypical CALMs (OR = 2, P = 0.09) were also more prevalent in the ASD group though not statistically significant.

Conclusion:

The presence of hyperpigmented pigmentary mosaicism and CALMs warrant closer surveillance by the caregivers and physicians for evolving features of autism. Larger multicentric studies are required to validate these findings.

Naevus vascularis mixtus and mixed vascular naevus syndrome

Naevus vascularis mixtus (NVM), or mixed vascular naevus (MVN), is a binary phenotype resulting from allelic twin spotting, consisting of a naevus anaemicus paired with a telangiectatic naevus reminiscent of naevus roseus, and caused by a mosaic GNA11 mutation. MVN syndrome is characterized by an NVM associated with soft tissue hypotrophy or central nervous system abnormalities, mainly involving the cerebral vasculature. The differential diagnoses of NVM and its syndrome include vascular twin naevi, syndromes featuring naevus flammeus and other port-wine naevi, and the various types of phacomatosis pigmentovascularis. NVM and MVN syndrome are rare but probably underdiagnosed and under-reported.

A six-attribute classification of genetic mosaicism

Mosaicism denotes an individual who has at least two populations of cells with distinct genotypes that are derived from a single fertilized egg. Genetic variation among the cell lines can involve whole chromosomes, structural or copy-number variants, small or single-nucleotide variants, or epigenetic variants. The mutational events that underlie mosaic variants occur during mitotic cell divisions after fertilization and zygote formation. The initiating mutational event can occur in any types of cell at any time in development, leading to enormous variation in the distribution and phenotypic effect of mosaicism. A number of classification proposals have been put forward to classify genetic mosaicism into categories based on the location, pattern, and mechanisms of the disease. We here propose a new classification of genetic mosaicism that considers the affected tissue, the pattern and distribution of the mosaicism, the pathogenicity of the variant, the direction of the change (benign to pathogenic vs. pathogenic to benign), and the postzygotic mutational mechanism. The accurate and comprehensive categorization and subtyping of mosaicisms is important and has potential clinical utility to define the natural history of these disorders, tailor follow-up frequency and interventions, estimate recurrence risks, and guide therapeutic decisions.

A Rare Case of Checkerboard-Like Becker Nevi with a Unique Distribution of Abnormalities

Becker nevus syndrome refers to a rare disorder comprising the typical pigmented lesion and its associated developmental abnormalities. Becker nevus itself is typically localized on the upper trunk, scapular or upper arm unilaterally; however, it can occasionally occur as multiple or bilateral lesions on any parts of the body. In this report, a rare case of multiple Becker nevi arranged in a unique checkerboard-like pattern is presented. More uniquely, the associated abnormalities found in this patient, breast hypoplasia and leg lipodystrophy, seem to be regionally correlated with the nevi. In closing, we would like to raise an easy-to-remember 6B's mnemonic, which stands for Becker, Breast, Bone, Bowen's disease, Basal cell carcinoma, and Beta-actin, for the cases of Becker nevus syndrome.

A neurocutaneous phenotype with paired hypo- and hyperpigmented macules, microcephaly and stunted growth as prominent features

Neurocutaneous disorders represent a heterogeneous group of conditions affecting the skin (with pigmentary/vascular abnormalities, hamartomas or tumors) and the central and peripheral nervous systems. In recent years, besides the well-known neurocutaneous diseases (e.g., the different forms of neurofibromatosis, tuberous sclerosis complex, Sturge-Weber syndrome and mosaic pigmentary/hamartomatous disorders), new distinctive syndromes have been characterized, extending our knowledge on the spectrum of these conditions. The concurrent presence of pigmentary abnormalities (both of the hypo- and hyperpigmented type), and primary microcephaly has not been commonly reported. We report on a 4.5-year-old girl with primary microcephaly, who had in addition moderate to severe developmental delay, behavioral and stereotypic abnormalities and a cutaneous pattern of paired hypo- and hyperpigmented lesions variously distributed over the body, particularly on the trunk. Failure to thrive and mild facial dysmorphic features were also present. To our knowledge, this complex malformation (neurocutaneous) phenotype has not been previously reported.