Clinical Quiz Answer
What is the Diagnosis?
Gorlin syndrome (OMIM# #109400): Our proband has mandibular odontogenic keratocyst, palmer pits, calcifications at anterior cerebral falx and tentorium, macrocephaly (2 cm above than 97th percentile line), medulloblastoma and congenital chest abnormalities. The first 3 phenotypes are considered as major phenotypes and the latter three are considered as minor from the diagnostic criteria in Table 1.1,2 These strongly suggest a diagnosis of Gorlin syndrome since it is diagnosed clinically when at least two major phenotypes or one major and two minor phenotypes are present.3 The clinical findings are then confirmed by targeted sequencing of the PTCH1 gene. (PreventionGenetics, USA) Results showed a two nucleotide deletion in nucleotide positions 665 and 666 (c.665_666delAT). This deletion changes the tyrosine at position 222 to serine, and at the same time causing a frameshift of the protein, leading to a premature stop after 29 amino acids (p.Tyr222Serfs*29). Although this mutation has not been reported before, however it is expected to be pathogenic and is consistent with diagnosis of Gorlin syndrome. Parental testing has not been done yet.
Gorlin syndrome was first reported by Gorlin and Goltz in 1960,4 although it was reported in as early as 1894.5 It is a condition that affects many areas of the body and has a predisposition in developing tumours, whether cancerous or noncancerous. The most common type of cancer found in Gorlin syndrome is a common form of skin cancer called basal cell carcinoma hence Gorlin syndrome is also called nevoid basal cell carcinoma syndrome. The prevalence of Gorlin syndrome varies amongst different populations, from 1 in 30,827 in the United Kingdom,6 to 1 in 164,000 in Australia,7 to 1 in 235,800 recently reported in Japan.8 The true prevalence of Gorlin syndrome may be even higher due to increased awareness leading to increased diagnosis as well as presence of mild cases which are difficult to detect in clinical settings.9
At birth, patients with Gorlin syndrome usually are found to have macrocephaly and/or ribs anomalies. Pits will become more evident in palms and soles of the feet as the patients age. Small number of patients will develop medulloblastoma at around 2 years of age and jaw keratocyst are found at around 10 years of age.8 By around 20 years of age, basal cell carcinoma may develop on the body, especially in the eye lids. Other tumours for example cardiac fibromas, meningioma and ovarian fibroma in females are also associated with Gorlin syndrome. Other important non-tumour features may include falx calcification, cleft lip/palate, frontal bossing, digits anomalies and ocular anomalies. Please see Table 1 for more features of Gorlin syndrome.1,2 Apart from the predisposition to tumours, life expectancy of patients with Gorlin syndrome does not significantly deviate from the average population.9
Gorlin syndrome, the "fifth phakomatosis", involves multiple systems and gives rise to interesting findings in different imaging modalities. The radiologic protocol for the diagnosis of this syndrome may include panoramic radiography to detect multiple keratocystic odontic tumours; skull X-ray (XR) for the evaluation of calcification; chest X-ray (CXR) to detect rib anomalies; computed tomography (CT) as well as magnetic resonance (MR) and ultrasound (USG) images to find further abnormalities. Premature ectopic calcification of the central nervous system (CNS) in form of calcifications along falx cerebri (70-80%), tentorium (20-40%), diaphragm sellae (60 to 80%) with bridging of sella turcica are very common abnormalities seen in CT brain of these patients.10 It is also associated with CNS neoplasms, mostly medulloblastoma (in 10% of cases). However, other CNS neoplasms like meningioma, astrocytoma and craniopharyngioma have also been reported with Gorlin syndrome. Apart from CNS tumours, US examinations of the pelvis of female patients may reveal ovarian fibromas. Cardiac echocardiography and Cardiac MR may be used to look for cardiac fibroma (relatively rare).
Keratocystic odontic tumours (KCOTs), formerly identified as odontogenic keratocysts, are one of the most consistent (appears in more than 90% of the cases) and early manifestations (usually in the second decade) of this syndrome.11 They usually present as uni- or multi-locular cysts, which may have a smooth or scalloped borders.10,12 The mandible is more commonly involved than maxilla and posterior involvement is more common than anterior. When in the mandible, they typically grow along the length of the bone. In the maxilla, they expand into the maxillary sinus. They are often associated with an impacted tooth, mimicking a dentigerous cyst.
Another common abnormality found in patients with Gorlin syndrome is rib anomalies include bifid, hypoplastic, fused, partially missing, or splayed ribs in 38-60% of patients; with the 3rd, 4th and 5th ribs most commonly affected and it may be unilateral or bilateral. Other skeletal anomalies including kyphoscoliosis, blocked vertebrae, hemivertebrae and spina bifida occulta, short fourth metacarpals, pectus deformity and Sprengel's deformity may be noted in other XRs. Flame shaped lucencies in phalanges, which are small, pseudocystic, lytic bone lesions, can also be seen on XR hands (30%) and feet (17%).13,14 Detailed radiological features detectable in Gorlin syndrome are summarised in Table 2.
The patched 1 (PTCH1; OMIM# *601309) gene is responsible for Gorlin syndrome and is located in the long arm of chromosome 9 (9q22.32). PTCH1 encodes for patched 1 which is the receptor protein of the sonic hedgehog (SHH) protein. When SHH binds to patched 1, a downstream protein smoothened (SMOH) is de-inhibited which in turns releases transcription factors Gli 1, 2 and 3 from the suppressor of fused homolog (SUFU) inhibitory protein.15 Gli1 is an activator and its level is found to be increased in brain and skin tumours.16 Gli2 is also an activator and is found to promote G1 to S phase transition in keratinocytes which may promote tumour development.17 Unlike the first two, Gli3 is a repressor and it is shown to repress the dHand and GREMLIN proteins which are involved in digits development.18 Mutation or absence of PTCH1 gene means absence of a functional patched 1 protein. The knock on effect causes uninhibited SMOH activity and continual up regulation of all 3 Gli transcription factors, causing tumour development as well as digit anomalies. Hence PTCH1 is regarded as a tumour suppressor gene.19 SHH signalling pathway via patched-1 is shown in Figure 3.15
Diagnosis of Gorlin syndrome is usually established in a clinical setting and diagnostic criteria have been published.2,3 A modified version of these criteria can be seen in Table 1.1,2 Both Evans, Ladusans et al (1993) and Kimonis, Goldstein et al (1997) proposed that Gorlin syndrome can be clinically confirmed when 2 major or 1 major and 2 minor phenotypes are present from the diagnostic criteria. Once a diagnosis has been made clinically, molecular testing can be used for confirmation. Targeted sequencing of PTCH1 gene is usually the first approach where exons 1 to 23 of PTCH1 gene are sequenced and has a detection rate of 50-85%.9 If sequencing analysis fails to detect the mutation, deletion/duplication analysis for large gene deletions can be considered and it has a detection rate of 6%-21%. However there have been cases where PTCH1 gene analysis found no mutation, and analysis of another component of the SHH pathway revealed a mutation in the SUFU gene found in chromosome 10q24.32.20 And it has been shown that cases with nodular or desmoplastic medulloblastoma caused by SUFU mutation exhibits some features of Gorlin syndrome.21 A non-functional SUFU protein from a mutated SUFU gene may cause uninhibited Gli transcription factors functions similar to that of PTCH1 mutation. The testing strategy is similar to PTCH1 where sequencing analysis is performed first followed by deletion/duplication analysis.
Treatments for Gorlin syndrome are usually supportive, aiming to reduce the presenting symptoms rather than curing them. An experienced specialist should be involved. One such treatment is the treatment for basal cell carcinomas which early treatment is essential to prevent long term cosmetic problems, especially for basal cell carcinomas found on the face. The aim is to completely eradicate aggressive basal cell carcinomas while persevering normal tissues to prevent disfigurement. Accompanying surgical treatments are cryotherapy and laser treatment for early lesions and photodynamic therapy. Moh's microsurgery has been proven to be particularly effective.22 Another presenting symptom that requires surgical treatment is keratocyst. Although they may be a painless swelling, if untreated, keratocysts may lead to major tooth disruption and jaw fracture. Due to the sensitively of basal cell carcinomas to radiography, thousands of basal cell carcinomas may develop at the radiation field and therefore radiotherapy should be avoid at all cost, especially in childhood.23 However if no other option is available, radiotherapy should be used with as few skin ports as possible.9 Diagnostic X-rays may also trigger development of basal cell carcinomas, therefore it should be used sparingly. Individuals are also advised to avoid direct sun exposure and administrate precautions since excessive sun exposed may trigger basal cell carcinomas. Precautions may include wearing long sleeves, high collars, and hats and complete sunblock should be used. Full discussion on treatment and management suggestions of Gorlin syndrome is beyond the scope of this clinical quiz. For more details, readers are suggested to read the guideline published by Bree and Shah (2011).24
Apart from clinical managements, proper genetic counselling should also be provided to the patients as well as the families. Gorlin syndrome is inherited in an autosomal dominant pattern. Only one copy of the genes in chromosome 9 has to be mutated in an affected individual and they have 50% chance of passing on the mutated gene to their offspring. Although at least one parent of affected children is affected in 70%-80% of cases, the remaining 20%-30% of cases are reported to have a de novo mutation.9 The siblings of patients also have 50% chance of being affected as well. Therefore genetic testing should be provided for the patients as well as the whole family.
We would like to thank the patient and the family for their contribution.
1. Basal Cell Carcinoma Nevus Syndrome (BCCNS) Life Support Network. Available from: http://www.gorlinsyndrome.org/.
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17. Regl G, Kasper M, Schnidar H, et al. The zinc-finger transcription factor GLI2 antagonizes contact inhibition and differentiation of human epidermal cells. Oncogene 2004;23:1263-74.
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19. Taylor MD, Liu L, Raffel C, et al. Mutations in SUFU predispose to medulloblastoma. Nat Genet 2002;31:306-10.
20. Pastorino L, Ghiorzo P, Nasti S, et al. Identification of a SUFU germline mutation in a family with Gorlin syndrome. Am J Med Genet A 2009;149A:1539-43.
21. Brugieres L, Remenieras A, Pierron G, et al. High frequency of germline SUFU mutations in children with desmoplastic/nodular medulloblastoma younger than 3 years of age. J Clin Oncol 2012;30:2087-93.
22. Mohs FE, Jones DL, Koranda FC. Microscopically controlled surgery for carcinomas in patients with nevoid basal cell carcinoma syndrome. Arch Dermatol 1980;116:777-9.
23. Evans DG, Birch JM, Orton CI. Brain tumours and the occurrence of severe invasive basal cell carcinoma in first degree relatives with Gorlin syndrome. Br J Neurosurg 1991;5:643-6.
24. Bree AF, Shah MR; BCNS Colloquium Group. Consensus statement from the first international colloquium on basal cell nevus syndrome (BCNS). Am J Med Genet A 2011;155A:2091-7.