Naevoid basal-cell carcinoma syndrome with unilateral neoplasms and pits

Genetic profiling of basal cell carcinomas detects postzygotic mosaicism in basal cell naevus syndrome

Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene. Postzygotic mosaicism can also cause BCNS. Here we describe two patients, one with multiple basal cell carcinomas (BCCs) and one with clinical BCNS, who had no PTCH1 mutation in DNA extracted from blood. In both patients, we performed genetic analysis on different BCCs, revealing the presence of a shared PTCH1 mutation in all tumours. Our findings show that in patients with symptoms of BCNS and initial absence of a PTCH1 mutation in blood, genetic profiling of BCCs can detect postzygotic mosaicism. What's already known about this topic? Basal cell naevus syndrome (BCNS) is associated with germline mutations in the PTCH1 gene, but it can also be caused by low-grade postzygotic mosaicism in PTCH1. What does this study add? In patients suspected of having BCNS or patients with multiple basal cell carcinomas (BCCs) with a special distribution on the body and no mutation detected in blood, it is worthwhile to search for a shared PTCH1 mutation in their BCCs as this can detect postzygotic mosaicism. This information is important to ensure proper surveillance programmes, choose the right therapy and provide adequate genetic counselling.

The concept of type 2 segmental mosaicism, expanding from dermatology to general medicine

In autosomal dominant skin disorders, the well-known type 1 segmental mosaicism reflects heterozygosity for a postzygotic new mutation. By contrast, type 2 segmental mosaicism originates in a heterozygous embryo from an early postzygotic mutational event giving rise to loss of the corresponding wild-type allele, which results in a pronounced segmental involvement being superimposed on the ordinary, non-segmental phenotype. Today, this concept has been proven by molecular analysis in many cutaneous traits. The purpose of this review was to seek publications of cases suggesting an extracutaneous manifestation of type 2 segmental mosaicism. Case reports documenting a pronounced extracutaneous segmental involvement were collected from the literature available in PubMed and from personal communications to the author. Pertinent cases are compared to the description of cutaneous segmental mosaicism of type 1 or type 2 as reported in a given trait. In total, reports suggesting extracutaneous type 2 segmental mosaicism were found in 14 different autosomal dominant skin disorders. In this way, clinical evidence is accumulated that extracutaneous type 2 segmental mosaicism does likewise occur in many autosomal dominant skin disorders. So far, however, molecular proof of this particular form of mosaicism is lacking. The present review may stimulate readers to inform colleagues of other specialties on this new concept, in order to initiate further research in this particular field of knowledge that has important implications for diagnosis, treatment and genetic counselling.

Postzygotic mosaicism in basal cell naevus syndrome

Basal cell naevus syndrome (BCNS) is an autosomal dominant disorder most commonly caused by a germline mutation in the Drosophila homologue of patched-1 gene (PTCH1). Here we describe a patient with clinical signs of BCNS, caused by postzygotic mosaicism of a PTCH1 mutation. We performed restriction fragment length polymorphism analysis and Droplet Digital polymerase chain reaction to determine the degree of mosaicism in different tissues of this patient. Our case shows that a relatively low-grade mosaicism can lead to clinical signs reminiscent of those caused by a germline mutation. This finding has important implications for genetic counselling and therefore is pivotal to recognize for dermatologists, as well as for clinical geneticists and clinical laboratory geneticists.

Molecular evidence of type 2 mosaicism in Gorlin syndrome

We present a 12-year-old girl with a family history of Gorlin syndrome who had unilateral, segmentally arranged basaloid skin tumours present since birth, ipsilateral, palmoplantar pits of rather large size distributed along Blaschko lines, and an ipsilateral odontogenic keratocyst. The patient and her father were heterozygous for a germline mutation in the form of a single-base substitution in exon 18 of the PTCH1 gene. In the patient's lesional skin, a microdeletion in exon 3 of PTCH1 was detected, giving rise to a truncated protein. This additional mutation was ruled out in the contralateral skin and in blood lymphocytes, thus confirming its mosaic state. In this way we provide for the first time molecular proof of a type 2 segmental involvement of this autosomal dominant trait.

Multiple fibroepithelial basal cell carcinoma of Pinkus associated with seborrheic keratosis in a nevoid distribution

We describe a patient with multiple fibroepithelial basal-cell carcinoma (FEBCC) associated with seborrheic keratosis distributed in a neviform fashion on the left side of the body and clinically resembling skin tags.

Lines of Blaschko

The lines of Blaschko represent a pattern followed by many skin disorders. We review the clinical and histologic features of X-linked, congenital/nevoid, and acquired skin diseases that follow these lines. We also include cutaneous disorders that have a linear distribution but do not follow Blaschko's lines. Finally, we differentiate Blaschko's lines from other patterns on the skin such as dermatomes and Langer's lines.

Unilateral dysplastic nevi associated with malignant melanoma

A case of dysplastic nevi associated with malignant melanoma was reported. The case was characterized by unilateral distribution of dysplastic nevi. Multiple dysplastic nevi were observed only dorsally on the patient's left upper quadrant. To the best of our knowledge, the report of this form of dysplastic nevi is the first in Japan. In addition, dysplastic nevus cell nests were present in histologic contiguity with intraepidermal proliferation of melanoma in the radial growth phase. Histological evidence suggested that the melanoma in our case had probably been derived from the context of dysplastic nevus.

Unilateral naevoid basal-cell-carcinoma syndrome--an individually controlled study of fibroblast sensitivity to radiation

A patient with unilateral naevoid basal-cell-carcinoma syndrome (NBCCS, Gorlin's syndrome) provided a unique opportunity to compare the radiation sensitivity of fibroblasts from the affected and unaffected sides of the same individual. Although the growth rate of the fibroblast strain established from the affected side was faster than that from the unaffected side there was no difference in X-ray, UV-B or UV-C radiation sensitivity between fibroblasts from the two sides. These results are discussed in the context of previous studies of radiation sensitivity in NBCCS.

Benzo(a)pyrene metabolism, DNA-binding and UV-induced repair of DNA damage in cultured skin fibroblasts from a patient with unilateral multiple basal cell carcinoma

The metabolism of benzo(a)pyrene (BP), a ubiquitous environmental carcinogen, and its subsequent binding to DNA, and the repair of UV-induced DNA damage were studied in fibroblasts cultured from the skin of a 61-year-old male who had multiple BCC (greater than 100) on his left upper trunk. Biopsies were obtained and fibroblasts cultured from clinically normal tumour-free skin adjacent to tumour-bearing sites (TBS) and from visibly uninvolved normal skin (UNS) at distant sites. The cultured cells were incubated with [3H]-BP for 24 h and BP metabolism was assessed by HPLC and the formation of BP-diols, quinones and phenols verified. Total BP metabolism was 45% lower in TBS fibroblasts than in UNS fibroblasts. The formation of BP-7,8-diol, the precursor of the carcinogenic end product of BP metabolism, was 53% lower in TBS cells than in UNS cells. Pretreatment of UNS cells with benz(a)anthracene (BA) (x 10(-4) M) did not significantly affect BP metabolite formation whereas BA-treatment of TBS cells resulted in 55% and 76% increases in total BP metabolism and BP-7,8-diol formation, respectively. Treatment of TBS cells with BA also caused a substantial increase (95%) in BP-DNA adduct formation. Whereas DNA-binding in UNS cells was unaffected by this treatment. In response to irradiation with 2J/m2 UVC, total DNA repair was similar in both cell types; on alkaline elution it appeared that the TBS cells were more efficient in repairing UV-induced DNA strand breaks. These results suggest that BP metabolism and repair of DNA are altered in TBS cells and that patients with this type of metabolic profile may be at higher risk of the development of cutaneous neoplasms. It is also possible that fibroblasts from tumour bearing skin undergo some as yet unexplained alteration in carcinogen metabolism as a consequence of the induction of neoplasia.