Gorlin-like phenotype in a patient with a PTCH2 variant of uncertain significance

Gorlin syndrome, also known as Nevoid Basal-Cell Carcinoma Syndrome (NBCCS), is an autosomal dominant tumor predisposition syndrome that presents early in life with characteristic congenital malformations and tumors. This syndrome most commonly results from germline mutations of the PTCH1 tumor suppressor gene, which shows high penetrance and great intra and interfamilial phenotypic variability, as well as the SUFU tumor suppressor gene. Recently, the PTCH2 gene has also been implicated as a cause of Gorlin syndrome. Notably, these patients displayed milder phenotypes of Gorlin syndrome when considered against PTCH1 and SUFU-related disease.We report a patient with a novel PTCH2 mutation inherited from his father. The proband displays several minor diagnostic features of Gorlin syndrome, supporting the pathogenic role of this gene. Features in the proband include macrocephaly, a wide face, prominent forehead, hypertelorism/telecanthus, large eyes, cleft lip and palate, thin vertical palmar creases, penoscrotal inversion, and a hyperpigmented spot on his penis. His father displays macrocephaly, several nevi on his back and shoulders, and a single palmar pit on his left hand, raising suspicion for Gorlin syndrome. Whole exome sequence (trio) found that the proband and father are heterozygous for NM_003738.4:c.3347C>T;p.(Pro1116Leu) in exon 21 of PTCH2, found also in his mildly affected brother. This semi-conservative amino acid substitution has been reported in the literature, but its significance is unclear. Notably, the proband, brother, and father do not meet clinical criteria for Gorlin syndrome. However, the clinical findings described in this family support the association between PTCH2 mutations and Gorlin-like phenotypes.     

Postnatal diagnosis of 9q interstitial imbalances involving PTCH1, resulting from a familial intrachromosomal insertion

Insertions are rare chromosomal rearrangements resulting from a three breaks mechanism. The risk of chromosomal imbalance in the offspring is estimated to be 15–50%. We have identified a familial history of direct, paracentric intrachromosomal 9q insertion, balanced in healthy members. For intrachromosomal insertions, unbalanced products in the offspring are always recombinants and in our case, reciprocal deletion and duplication of the inserted segment (9q22.31–9q31.1) were observed. These imbalances involved several genes, including PTCH1. PTCH1 haploinsufficiency causes Gorlin syndrome, an autosomal dominant disorder usually linked to the gene mutation but sometimes due to a 9q deletion. Clinical findings are different in 9q deletions and duplications including PTCH1, notably concerning the predisposition to benign and malignant tumors reported in the Gorlin syndrome. Furthermore, some features may be reciprocal. This history of intrachromosomal insertion highlights the importance of morphological cytogenetic analyses to provide an accurate genetic counseling.     

Novel Patched 1 mutations in patients with nevoid basal cell carcinoma syndrome – case report

Nevoid basal cell carcinoma syndrome (Gorlin syndrome) is a rare autosomal dominant disorder characterized by numerous basal cell carcinomas, keratocystic odontogenic tumors of the jaws, and diverse developmental defects. This disorder is associated with mutations in tumor suppressor gene Patched 1 (PTCH1). We present two patients with Gorlin syndrome, one sporadic and one familial. Clinical examination, radiological, and CT imaging, and mutation screening of PTCH1 gene were performed. Family members, as well as eleven healthy controls were included in the study. Both patients fulfilled the specific criteria for diagnosis of Gorlin syndrome. Molecular analysis of the first patient showed a novel frameshift mutation in exon 6 of PTCH1gene (c.903delT). Additionally, a somatic frameshift mutation in exon 21 (c.3524delT) along with germline mutation in exon 6 was detected in tumor-derived tissue sample of this patient. Analysis of the second patient, as well as two affected family members, revealed a novel nonsense germline mutation in exon 8 (c.1148 C>A).Nevoid basal cell carcinoma syndrome (NBCCS; Gorlin syndrome; MIM 109400) is a rare autosomal-dominant disorder with the prevalence ranging from 1/57 000 to 1/256 000 and a male-to-female ratio of 1:1 (1,2). It is characterized by a multiple basal cell carcinomas (BCCs), developmental and skeletal anomalies, keratocystic odontogenic tumors (KCOT) of the jaws, and a predisposition to a variety of other tumors (3). NBCCS may affect multiple organ systems, such as skin, skeletal system, genitourinary system, and central nervous system. It is caused by mutations in the Patched 1 (PTCH1) gene, a tumor suppressor gene involved in Sonic hedgehog (SHH) signaling pathway (4,5). Mutations of PTCH1 gene have also been associated with sporadic carcinomas, such as keratocystic odontogenic tumor (KCOT) (6), medulloblastoma (7), esophageal squamous cell carcinoma (8), and some benign tumors, such as ovarian and cardiac fibromas. To date, over 230 PTCH1 germline mutations associated with NBCCS have been reported (9), which are transmitted in an autosomal-dominant way with high penetrance and variable expressivity (10-12). We present two cases with Gorlin syndrome, one sporadic and one familial. Molecular diagnosis in patients and family members was established by molecular genetic analysis.     

PTCH mutations: distribution and analyses

Mutations in the PTCH (PTCH1) gene are the underlying cause of nevoid basal cell carcinoma syndrome (NBCCS), and are also found in many different sporadic tumors in which PTCH is thought to act as a tumor suppressor gene. To investigate the distribution pattern of these mutations in tumors and NBCCS, we analyzed 284 mutations and 48 SNPs located in the PTCH gene that were compiled from our PTCH mutation database. We found that the PTCH mutations were mainly clustered into the predicted two large extracellular loops and the large intracellular loop. The SNPs appeared to be clustered around the sterol sensing domain and the second half of the protein. The NBCCS cases and each class of tumor analyzed revealed a different distribution of the mutations in the various PTCH domains. Moreover, the types of mutations were also unique for the different groups. Finally, the PTCH gene harbors mutational hot spot residues and regions, including a slippage-sensitive sequence in the N-terminus.     

Analysis of PTCH/SMO/SHH pathway genes in medulloblastoma

Inactivation of the PTCH tumor suppressor gene occurs in a subset of sporadic medulloblastomas, suggesting that alterations in the PTCH pathway may be important in the development of this tumor. In order to address the frequency of genetic alterations affecting genes in this pathway, we used a combination of loss of heterozygosity (LOH) analysis, single-stranded conformational polymorphism (SSCP) analysis, and direct sequencing of DNA samples from sporadic primitive neuroectodermal tumors (PNETs). To identify alterations in the PTCH gene, we performed LOH analysis on 37 tumor DNA samples. Of those with matched constitutional DNA samples, one demonstrated LOH. Of those without matched constitutional DNA, six were homozygous with all markers. All exons of the PTCH gene were sequenced in these seven tumors, and three mutations were found. To identify alterations in the SHH and SMO genes, we analyzed all exons of both genes in 24 tumors with SSCP and sequenced any exons that showed aberrant band patterns. No mutations were found in either SHH or SMO in any tumor. We also identified the following genes as candidate tumor suppressors based on their roles in controlling hh/ptc signaling in Drosophila: EN-1 and EN-2, deletion of which results in a lack of cerebellar development in mice; SMAD family members 1-7, and protein kinase A subunits RIalpha, RIbeta, RIIbeta, Calpha, and Cbeta. Each of these genes was investigated in a panel of 24 matched constitutional and tumor DNA samples. Our search revealed no mutations in any of these genes. Thus, PTCH is the only gene in this complex pathway that is mutated with notable frequency in PNET. Genes Chromosomes Cancer 27:44-51, 2000.     

Novel PTCH1 mutations in Japanese Nevoid basal cell carcinoma syndrome patients: two familial and three sporadic cases including the first Japanese patient with medulloblastoma

Nevoid basal cell carcinoma syndrome (NBCCS), also known as Gorlin syndrome, is inherited in an autosomal dominant mode, and is characterized by a combination of developmental abnormalities and predisposition to form a variety of tumors. The hedgehog receptor Patched1 (PTCH1) has been identified as the gene mutated in NBCCS. We analyzed PTCH1 in two familial and three sporadic Japanese NBCCS cases, and identified five germline mutations in PTCH1. Two cases have a nonsense mutation (c.3058C>T and c.2760C>A), one a splice site mutation (c.584+2T>G), one a 1 bp insertion (c.2712_2713insA) and one a 1 bp deletion (c.980Gdel). All mutations induce truncation of the PTCH1 protein or could induce nonsense-mediated mRNA decay. The 11-year-old male patient with splice-site mutation (c.584+2T>G) had medulloblastoma (MB) at the age of 1 year. This is the first NBCCS patient with molecularly defined MB in Japan.     

PTCH mutations are not mainly involved in the pathogenesis of sporadic trichoblastomas

Trichoblastomas are rare, benign tumors of the appendix in human skin. The histopathology comprises elements of basal cell carcinoma and trichoepithelioma with a variable degree of follicular differentiation. Both basal cell carcinoma and trichoepithelioma reveal alterations of PTCH, the human homolog of the Drosophila segment polarity patched gene. Furthermore, heterozygous PTCH knockout mice develop trichoblastoma-like tumors. This suggests an involvement of the PTCH gene in the pathogenesis of human trichoblastomas. However, trichoblastomas arising in nevus sebaceus did not show loss of heterozygosity at the PTCH locus (9q22.3) in a previous study. Sequencing of the PTCH gene and analysis of sporadic human trichoblastomas have not been performed yet. We therefore screened 10 sporadic trichoblastomas and 1 trichoblastoma arising within a nevus sebaceus for PTCH mutations. After microdissection of the tumors, single-strand conformational polymorphism (SSCP)/heteroduplex analysis of exons 2 to 23 of PTCH was performed, and polymerase chain reaction products with aberrant band patterns were sequenced. One trichoblastoma revealed a silent mutation at codon 562 in exon 12. Another trichoblastoma showed a somatic C > T single nucleotide substitution at codon 1,315 (exon 23), which was not present in corresponding normal epidermis. This mutation at codon 1,315 represents an already described PTCH germline polymorphism and results in a heterozygous Pro to Leu substitution in the tumor. The Pro/Leu polymorphism in germline is associated with a higher risk for breast cancer, but a potential contribution to the tumorigenesis of trichoblastoma is unknown. We detected no classical PTCH mutations in the investigated trichoblastomas. Our results indicate that PTCH mutations are not mainly involved in the pathogenesis of sporadic trichoblastomas, in contrast to basal cell carcinomas and trichoepitheliomas. The genetic basis of this rare appendageal tumor remains elusive.     

Detecting tissue-specific alternative splicing and disease-associated aberrant splicing of the PTCH gene with exon junction microarrays

Mutations in the human ortholog of Drosophila patched (PTCH) have been identified in patients with autosomal dominant nevoid basal cell carcinoma syndrome (NBCCS), characterized by minor developmental anomalies and an increased incidence of cancers such as medulloblastoma and basal cell carcinoma. We identified many isoforms of PTCH mRNA involving exons 1-5, exon 10 and a novel exon, 12b, generated by alternative splicing (AS), most of which have not been deposited in GenBank nor discussed earlier. To monitor splicing events of the PTCH gene, we designed oligonucleotide arrays on which exon probes and exon-exon junction probes as well as a couple of intron probes for the PTCH gene were placed in duplicate. Probe intensities were normalized on the basis of the total expression of PTCH and probe sensitivity. Tissue-specific regulation of AS identified with the microarrays closely correlated with the results obtained by RT-PCR. Of note, the novel exon, exon 12b, was specifically expressed in the brain and heart, especially in the cerebellum. Additionally, using these microarrays, we were able to detect disease-associated aberrant splicings of the PTCH gene in two patients with NBCCS. In both cases, cryptic splice donor sites located either in an exon or in an intron were activated because of the partial disruption of the consensus sequence for the authentic splice donor sites due to point mutations. Taken together, oligonucleotide microarrays containing exon junction probes are demonstrated to be a powerful tool to investigate tissue-specific regulation of AS and aberrant splicing taking place in genetic disorders.     

Loss of the PTCH1 gene locus in cardiac fibroma.

BACKGROUND: Cardiac fibroma (CF) is a rare benign tumor that is poorly characterized genetically. CF is more commonly encountered in patients with Gorlin syndrome (3%) than the general population. Mutations of the tumor suppressor gene PTCH1 are the underlying cause of Gorlin syndrome. METHODS: Conventional cytogenetic analysis was performed on a peripheral blood and a CF sample from a 2-week-old male. In addition, fluorescence in situ hybridization (FISH) studies were performed to assess the copy number of the PTCH1 gene locus (9q22.3) on metaphase and interphase cells from these same specimens using yeast artificial protein (YAC) probe 891G1 and on representative paraffin-embedded tissue sections of two additional CFs (one arising in a 2-month-old female and the other in a 13-week-old male). None of the patients had Gorlin syndrome. RESULTS: Karyotypically, the following abnormal chromosomal complement was detected in the 2-week-old male's CF: 46,XY,del(9)(q22q34)[15]. FISH studies revealed homozygous loss of the PTCH1 locus in the cytogenetically analyzed CF and in the CF arising in the 13-week-old male. Heterozygous loss of this locus was identified in the remaining CF from the 2-month-old female. A mutational mechanism other than deletion may be responsible for PTCH1 inactivation on the other locus in this latter patient. Conventional cytogenetic and FISH studies of the peripheral blood sample from the 2-week-old male were normal. CONCLUSION: These data support a tumor suppressor gene role for PTCH1 in nonsyndromic or sporadic CFs.     

Involvement of PTCH gene in various noninflammatory cysts

Constitutional hemizygous inactivation of PTCH, the Shh signaling pathway gene that moderates the signal, manifests itself as nevoid basal cell carcinoma syndrome or Gorlin syndrome, a condition variably characterized by a number of developmental disorders and malformations, and by predisposition to some malignancies, basal cell carcinoma in particular. Loss of heterozygosity for the PTCH region was found several years ago in the epithelial lining of odontogenic keratocysts, the cyst type with highly increased incidence in nevoid basal cell carcinoma syndrome. This finding confirmed the expectations that the gene responsible for the syndrome would have a decisive role in the genesis of these cysts even when they are not syndrome related. Suggestive temporal distribution of Shh signaling, recently observed during tooth development, lead us to investigate PTCH association with dentigerous cysts, the other major noninflammatory cyst of odontogenic origin. We report here that PTCH appears to be inactivated in dentigerous cysts, suggesting that it is responsible for their genesis as well. More generally, if our similar observations of incomplete heterozygosity in this region for dermoid cysts can be interpreted as loss of heterozygosity, PTCH alterations may prove to be a necessary, and perhaps the initiating event, in formation and growth of various noninflammatory cysts. This would be consistent with our view that local PTCH inactivation can, under favorable circumstances, lead to persistent though not by itself truly aggressive cell proliferation.     

Gorlin syndrome: identification of 4 novel germ-line mutations of the human patched (PTCH) gene. Mutations in brief no. 137. Online

PTCH, the human homologue of the Drosophila segment polarity gene, patched, has been identified as the gene responsible for Gorlin or nevoid basal cell carcinoma syndrome (NBCCS). We report here the characterization of four novel mutations in the human PTCH gene in germ-line DNA from Gorlin patients. All mutations lead to truncation of the predicted protein product. Also included is a list of putative polymorphic nucleotide postions in the sequence covered by published primers.     

Microdeletion of 22q11.1 is associated with two cases of familial nonsyndromic basal cell carcinoma

Multiple basal cell carcinomas (BCCs) are a hallmark of Gorlin syndrome (nevoid basal cell carcinoma syndrome), which is caused by mutation in the PTCH1 gene on 9q22.3. However, there are several reports of familial cases with multiple BCCs without the associated defects of Gorlin syndrome. The possibility of underlying genetic abnormalities in these familial BCCs has not been explored previously. The present study investigated a possible genetic abnormality in two members of a family with multiple nonsyndromic BCCs. The possibility of Gorlin syndrome in this family was excluded by both the absence of any clinical and radiological features and the lack of mutation in PTCH1. Notably, whole-genome comparative genomic hybridization (CGH) identified a microdeletion in chromosome 22q11.1 in both of the studied cases. A tiling path CGH array of the 22q11.1 region confirmed this microdeletion and mapped it between 14.46 and 14.5 Mb on chromosome 22q. The 34-kb region of this microdeletion includes three annotated genes: LOC644525, LOC100132389, and LOC729057. Although future studies of other families with the hereditary nonsyndromic BCCs are still warranted, this study identified an association between a microdeletion of 22q11.1 and two familial cases of BCC.     

Expression patterns and polymorphisms of PTCH in Chinese hepatocellular carcinoma patients

Aberrant activation of Hedgehog signaling pathway leads to pathological consequences in a variety of human tumors. PTCH (PTCH1), the receptor of Hedgehog pathway, is reported to function as a gatekeeper in tumor formation. Here we report, by semi-quantitative RT-PCR, PTCH expression was found in 38 hepatocellular carcinoma (HCC) patients (66%). Evidences from real time quantitative RT-PCR further indicate that compared to their matched nontumorous liver tissue, PTCH exhibit a higher expression in well and moderate differentiated tumor, but a lower expression in poorly differentiated tumor. Immunohistochemical staining showed PTCH protein was detected in the cytoplasm of 56.3% HCC samples (9/16). For the first time, we investigate the polymorphisms of PTCH in HCC. First we sequenced the recognized mutation hot spots regions of PTCH of 38 HCC samples. Two previously reported single nucleotide polymorphisms (SNPs) and a novel SNP A1056G were identified. Then we examined these three SNPs in 171 HCC samples and 162 normal liver samples. However, statistic analysis showed none of these SNPs was statistically significant for association with HCC. In conclusion, our data suggest that PTCH is involved in early stage tumor development and the Hh pathway in Chinese HCC is activated by ligand expression but not by mutation.     

Mutations in the human homologue of Drosophila patched in Japanese nevoid basal cell carcinoma syndrome patients

Mutations in the human homologue of Drosophila patched (PTCH) have been identified in patients with nevoid basal cell carcinoma syndrome (NBCCS; also called Gorlin syndrome) as well as sporadic basal cell carcinomas and medulloblastomas. However, using PCR-SSCP analysis, mutations in PTCH have been found in only a fraction (about one third to a half) of NBCCS patients. In this study, we determined the whole genomic organizations of the PTCHgene and developed a new set of more accurate primers for the analysis of mutations in PTCH. Using these primers, we examined 8 Japanese NBCCS patients for mutations in all PTCH exons by direct sequencing of the PCR products. As a result, we identified 5 novel PTCH mutations in 6 out of 8 patients including 2 sisters as well as 5 polymorphisms, two of them, 1704G>C and 2928G>C were novel. Four of these mutations, 900delC, 1247insT, 1999delC and 933+5G>T, cause protein truncation due to the insertion or deletion of a single nucleotide or aberrant splicing. The remaining mutation, 1514G>A was a missense alteration (G509D). Interestingly, the amino acid substitution, G509V, has been reported previously in an NBCCS patient, suggesting an important role of this amino acid residue in the function of PTCH protein. The difference in the detection rate of PTCH mutations among NBCCS between previous reports and ours is due to the difference either in ethnicity or in the detection methods.     

Downregulation of the hedgehog receptor PTCH1 in colorectal serrated adenocarcinomas is not caused by PTCH1 mutations

Colorectal serrated adenocarcinoma forms about 15–20% of colorectal carcinomas. We have previously shown that downregulation of PTCH1 is distinctive for this type of colorectal cancer. In several other tumor types, somatic inactivating PTCH1 mutations have been shown to lead to aberrant Hedgehog signaling, but in colorectal cancer the role of PTCH1 mutations has not been thoroughly studied. Here, we have analyzed the mutation status of PTCH1 in a series of 33 colorectal serrated adenocarcinomas by sequencing all 23 coding exons. We detected 11 previously known SNPs and eight new alterations. The latter included five synonymous changes and two previously unknown missense variations, somatic M319V, and germline V1231A. V1231A was also present in population controls and likely represents polymorphism. The somatic M319V variant does not appear to be an attractive candidate for a disease-associated mutation because in silico analyses did not support the pathogenic nature of the change. A somatic, intronic 1-bp deletion was detected in a short poly(T) stretch in two microsatellite unstable tumors. None of the three changes had predicted effect on splicing when analyzed in silico. Our results did not reveal any clearly deleterious inactivating PTCH1 mutations in our collection of colorectal serrated adenocarcinomas. This suggests that other mechanisms are involved in the observed downregulation of the PTCH1 gene. These might include, e.g., constantly active MAPK signaling by KRAS or BRAF mutations or silencing of PTCH1 by hypermethylation, and further studies are needed to reveal these mechanisms.     

Is PATCHED an important candidate gene for neural tube defects? Cranial and thoracic neural tube defects in a family with Gorlin syndrome: a case report

. The relationship of mutations in the patched gene PTCH and nevoid basal cell carcinoma (NBCC) or Gorlin syndrome is well established. Animal studies have implicated the hedgehog-patched signalling pathway in neurulation and neural tube defects (NTDs). Spina bifida occulta and bifid vertebrae are well recognized in NBCCS, but there appears to be only one report of open spina bifida. We report a father and two sons with a truncating PTCH mutation and the major features of NBCCS. One son had open thoracic spina bifida and the other had an occipital meningocoele. We believe this to be the first report of cranial NTD in NBCCS and suggest that consideration be given to including PTCH analysis in genetic association studies in NTDs as the hedgehog pathway is integral to normal human neurulation.     

Methylation of PTCH1, the Patched-1 gene, in a panel of primary medulloblastomas

The Sonic hedgehog (Shh) pathway is aberrantly activated in a subset of the most common malignant pediatric brain tumor, medulloblastoma (MB). Shh pathway activity is measured by expression of the target genes in the GLI family, MYCN and PTCH1, a tumor suppressor and negative regulator of the pathway. Promoter methylation of tumor suppressors is implicated in tumor formation by gene silencing. In this study, we examined whether the proximal promoter of the PTCH1 gene (variant exon 1B) is methylated in some cases of MB. The cases in which we anticipated the highest likelihood of methylation were chosen based on gene expression of indicators of Shh pathway activity. Of 21 primary MBs, four exhibited robust mRNA expression of GLI1 and MYCN as well as low or absent PTCH1 expression, suggesting Shh pathway activity in the absence of PTCH1. The methylation profile of these cases was determined by the bisulfite sequencing method and compared to the profiles of five unaffected pediatric cerebellum controls. Contrary to our hypothesis, there was no evidence of methylation in the PTCH1-1B promoter in the MB cases examined, nor was there methylation in the control cerebellum samples. Future directions include examination of distal regions of the PTCHlb promoter as well as alternative exon variants, most notably the CpG island containing PTCH1-1C promoter.     

Selective haploinsufficiency of longer isoforms of PTCH1 protein can cause nevoid basal cell carcinoma syndrome

Nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant disorder characterized by developmental defects and tumorigenesis. The gene responsible for NBCCS is PTCH1. The PTCH1 gene has five alternatively used first exons resulting in the translation of three isoforms of the PTCH1 protein; that is, PTCHL, PTCHM and PTCHS. However, the biological significance of each isoform is unclear. Here we show an individual with NBCCS carrying a nonsense mutation in PTCH1 exon2, c.387G>A (p.W129X). As the mutation lay upstream of the ATG codon used for PTCHS translation, the mutant allele still expressed RNA isoforms that encode PTCHS. These results clearly demonstrate that a selective haploinsufficiency of longer isoforms of the PTCH1 protein, PTCHL and PTCHM, but not PTCHS is sufficient to cause NBCCS. Although mice selectively deficient in PTCHS isoforms are currently unavailable, this study sheds light on the complex in vivo roles of PTCH1 isoforms.     

Gorlin syndrome with ulcerative colitis in a Japanese girl

We present the case of a 14-year-old Japanese girl who had both Gorlin syndrome and ulcerative colitis. She had complained of blood stools for 6 months and severe scoliosis from her infancy. Physical examination revealed multiple nevi, palmar and plantar pits, jaw cysts, and calcification of the falx cerebri, leading to the diagnosis of Gorlin syndrome. Total colonoscopy revealed an edematous and spotty bleeding mucosa extending from the anus to the transverse colon. Histological examination was also compatible with ulcerative colitis. Thus, we diagnosed her as having Gorlin syndrome with ulcerative colitis. Gene analysis revealed a mutation, 1247InsT, in the human patched gene (PTCH), resulting in the truncation of PTCH protein. Since Gorlin syndrome and ulcerative colitis are rare disorders in childhood, this association is interesting, suggesting a correlation between the hedgehog signaling and intestinal disorders.     

Patched mutations and hairy skin patches: a new sign in Gorlin syndrome

We report on the occurrence of discrete patches of unusually long pigmented hair on the skin of three patients with Gorlin syndrome from two unrelated families with confirmed heterozygous mutations in the Patched (PTCH) gene. The PTCH protein is a negative regulator of Hedgehog signaling, and the Sonic Hedgehog (SHH)-PTCH pathway is known to play an important role in the formation and cycling of the hair follicle. We believe that the patches represent a genuine physical sign associated with Gorlin syndrome, and discuss molecular mechanisms by which they might arise.