Appreciating the broad clinical features of SMAD4 mutation carriers: a multi-center chart review

Abstract

Heterozygous loss-of-function (LOF) SMAD4 mutations are associated with juvenile polyposis syndrome (JP) and hereditary hemorrhagic telangiectasia (HHT). Some carriers exhibit symptoms of both conditions, leading to the name JP-HHT syndrome. Three families have been reported with connective tissue abnormalities. In order to better understand the spectrum and extent of clinical findings in SMAD4 carriers, medical records of 34 patients (20 families) from five clinical practices were reviewed. Twenty-one percent (7/34) had features suggesting a connective tissue defect: enlarged aortic root (n=3), aortic and mitral insufficiency (n=2), aortic dissection (n=1), retinal detachment (n=1), brain aneurysms (n=1), lax skin and joints (n=1). JP-specific findings were almost uniformly present but variable. Ninety-seven percent had colon polyps that were generally pan-colonic and of variable histology and number. Forty-eight percent (15/31) had extensive gastric polyposis. HHT features were documented in 76% including epistaxis (19/31, 61%), mucocutaneous telangiectases (15/31, 48%), liver arteriovenous malformation (AVM) (6/16, 38%), brain AVM (1/26, 4%), pulmonary AVM (9/17, 53%), and intrapulmonary shunting (14/23, 61%). SMAD4 carriers should be managed for JP and HHT, since symptoms of both are likely yet unpredictable. Connective tissue abnormalities are an emerging component of JP-HHT syndrome, and larger studies are needed to understand these manifestations.

INTRODUCTION

Juvenile polyposis (JP) (OMIM #174900) and hereditary hemorrhagic telangiectasia (HHT) (OMIM #187300 and #600376) are distinct syndromes caused by mutations in genes within the TGF-β signaling pathway. Several published case reports, beginning in 1980, describe patients with features of both JP and HHT.^1–6 Given the rarity of both syndromes and the existence of several reports of patients with features of both disorders, it was suspected that a distinct syndrome combining these two entities might exist. A combined syndrome of JP-HHT, caused by SMAD4 mutations, is now recognized as a distinct entity (OMIM #175050).^7–13

Juvenile polyposis (JP) is a genetically heterogeneous autosomal dominant hamartomatous polyposis syndrome characterized by multiple gastrointestinal polyps of juvenile histology. Patients typically present in the first or second decade of life¹⁴ with symptoms including rectal bleeding, anemia, prolapse, abdominal pain, diarrhea, and intussusception.^15,16 In general, polyps are typically distributed evenly throughout the colon, and less commonly found in the small intestine and stomach.¹⁴ However, there is a genotype-phenotype correlation between SMAD4 mutations and severe gastric polyposis.^29–31 The total number of polyps varies greatly, from a few to hundreds.¹⁴ Historically, the estimated lifetime risk for gastrointestinal malignances for individuals with JP has ranged from 39–68%; however, this risk has shown to be significantly reduced through increased surveillance.^{17,18, 31} Approximately half of patients meeting clinical criteria for JP have identifiable mutations in the SMAD4 or BMPR1A genes.¹⁹

Hereditary hemorrhagic telangiectasia (HHT) is also a genetically heterogeneous autosomal dominant disorder. It leads to vascular dysplasia characterized by mucocutaneous telangiectases of the fingertips, lips, oral mucosa, and nose, and arteriovenous malformations (AVMs) of the lungs, brain, liver, gastrointestinal (GI) system, and spine.²⁰ Symptoms are not typically present at birth, but develop with increasing age.²⁰ The most common presenting symptom is epistaxis, occurring eventually in over 90% of patients and beginning on average at age 12.²¹ Serious complications may result if AVMs are unrecognized and untreated, including anemia, hemorrhage, brain abscess, transient ischemic attack, seizure, and stroke.²⁰ Approximately 80–85% of patients with a clinical diagnosis HHT have a mutation identifiable in the ENG, ACVRL1 (ALK1), or SMAD4 genes.²²

Recently, a small number of patients with SMAD4 mutations and the combined JP-HHT syndrome have been reported with various findings suggestive of connective tissue disorders, including aortic root dilation, thoracic aortic aneurysm, aortic dissection, skeletal features of Marfan syndrome, and mitral valve abnormalities.^23,24 Additionally, two individuals with SMAD4 mutations from a series of JP patients had arterial aneurysms, and three individuals (genotype not provided) had mitral valve prolapse.³¹ These findings have not been classically associated with the JP or HHT entities. All known genes causative of JP and HHT encode members of the TGF-β signaling pathway. Mutations in several other genes within this pathway, such as TGFBR1, TGFBR2, TGFB2, and SMAD3, cause familial thoracic aortic aneurysms and aortic dissections, which provides a possible explanation for this reported connection. These recent reports provided the foundation for the hypothesis that individuals with SMAD4 mutations might be susceptible to a broader range of medical issues than their presenting clinical features might indicate.

Clinical management recommendations have been published for JP and for HHT,^25,26 but given the genetic heterogeneity involved, and the paucity of data on which recommendations are made, we sought to increase the understanding of the SMAD4 mutation phenotype by identifying a meaningful number of SMAD4 mutation carriers and reviewing their medical histories.

METHODS

A retrospective multi-center chart review of SMAD4 mutation carriers was conducted at five clinical practices. Patients were evaluated in a variety of clinical settings, including HHT Centers, Medical Genetics, Gastroenterology, and Oncology Departments. These sites included Mayo Clinic Rochester (Rochester, MN), Mayo Clinic Florida (Jacksonville, FL), Huntsman Cancer Institute and HHT Center, University of Utah (Salt Lake City, UT), City of Hope (Duarte, CA), and the Royal Melbourne Hospital (Melbourne, Australia). This study was approved by the Mayo Clinic institutional review board and individually at the other sites if required. Electronic medical records were searched from 1996 to 2011 using a variety of terms including SMAD4, juvenile polyposis, and hereditary hemorrhagic telangiectasia. The diagnostic database from the Department of Medical Genetics at Mayo Clinic Rochester was also reviewed to identify potential cases. Cases from Huntsman Cancer Institute (HCI) were identified through the Hereditary Gastrointestinal Cancers Registry and had also undergone a clinical genetics evaluation at HCI. The City of Hope (COH) Clinical Cancer Genetics Community Research Network (CCGCRN) includes a cross section of cancer center and community-based clinics, and all genetic cancer risk assessment patients are invited to participate in an IRB-approved prospective registry at the time of consultation.²⁷

Inclusion criteria consisted of documentation of a pathogenic SMAD4 mutation and availability of the patient’s medical records for review. Patients with Myhre syndrome (OMIM # 139210; a disorder characterized by intellectual impairment, dysmorphic facial features, and skeletal anomalies that is caused by gain-of-function mutations in one specific codon in the SMAD4 gene) were excluded.

A total of 34 mutation carriers from 20 families were identified for inclusion. A standardized detailed chart abstraction form was created and data was abstracted from medical records at each institution. Data collected included age at evaluation/procedure, the specific SMAD4 mutation identified, clinical features of JP and HHT, and results of specific screening tests. In addition to a careful focus on SMAD4-associated pathology, such as neoplasms and connective tissue findings, the abstraction process also provided the opportunity for investigators to review and collect information on other types of medical diagnoses. Due to the multi-center and retrospective nature of this study and to patient and provider variability there was not a unified surveillance protocol followed for all patients.

RESULTS

Thirty-four SMAD4 mutation carriers from 20 families were identified and had charts available for review. The mean age at last visit was 35.1 years (range 0.1–74 years). Fourteen different mutations were identified; three mutations were reported in more than one family. Seven of these mutations have been reported previously in association with JP, JP-HHT, or HHT (Supplementary Materials and Methods). One individual is reportedly a member of a family originally published by Howe et al. (1998). He had declined genetic testing but has a clinical diagnosis and is a presumed carrier for the c.1372–1375delACAG mutation.²⁸

Clinical findings are summarized in Table 1. Twenty-one percent (7/34), from five separate families, had features of a connective tissue disorder, including enlarged aortic root (n=3), aortic and mitral insufficiency (n=2), fatal aortic dissection (n=1), retinal detachment (n=1), brain aneurysms (n=1), and lax skin and joints (n=1). These individuals were all between ages 42–65 years at the time of this study, although exact ages of onset for connective tissue findings were not noted. All five families had different mutations in various domains of the gene.

Table 1.

Clinical findings in SMAD4 mutation carriers

Clinical findings	Percent and number of individuals
Colon polyps	97% (31/32)
Gastric polyps	68% (21/31)
- Extensive polyposis	48% (15/31)
- 1–10 polyps	19% (6/31)
Small bowel polyps	39% (11/28)
Neoplasms	26% (9/34)
- Colorectal	9% (3/34)
- Hurthle cell thyroid	6% (2/34)
- Ovarian teratomas	3% (1/34)
- Lymphoma/jejunal	3% (1/34)
- Esophageal adenocarcinoma	3% (1/34)
- Pancreatic neoplasm	3% (1/34
Epistaxis	61% (19/31)
Telangiectases	48% (15/31)
AVMs
- Brain	4% (1/26)
- Lung	53% (9/17)
- Liver	38% (6/16)
Intrapulmonary shunt	61% (14/23)
HHT-related symptoms in absence of AVM/IP shunt	15% (5/34)
- Migraines	12% (4/34)
- Seizure	3% (1/34)
Connective tissue finding	21% (7/34)
- Enlarged aortic root	9% (3/34)
- Aortic/mitral insufficiency	6% (2/34)
- Aortic dissection	3% (1/34)
- Retinal detachment	3% (1/34)
- Brain aneurysms	3% (1/34)
- Lax skin & joints	3% (1/34)

Lower gastrointestinal polyps were reported in 97% of individuals who had undergone colonoscopy (31/32, identified at 4–51 years). Individuals underwent their first colon exam on average at age 23 (range 4–51 years) for one or more indications including anemia (n=8), GI bleeding +/− anemia (n=12), JP known or suspected (n=10), obstructive symptoms (n=3), and unknown (n=5). The most recent colon exams were conducted at a mean age of 36 years (range 6–73 years) and were completed within the last three years for all but three individuals. Polyps were generally pan-colonic and of variable histology. The total number of polyps ranged from one to over 1000 and did not appear to be age-associated; one individual (now 42 years old) was only 17 when over 1000 polyps were discovered. Polyps were present in all but one patient under the age of 21 who had a colonoscopy. When the number of polyps was available, 80% had less than 100 (16/20). Thirty-one individuals had gastric imaging and 28 had small bowel imaging, typically by upper endoscopy, with first exams performed at a mean age of 31 years (range 4–73 years) and 37 years (range 4–72 years), respectively. The most recent gastric and small bowel imaging studies were done within the last year for all but one individual. Indications for gastric and small bowel screening included bleeding, pain, or another physical symptom (n=10), screening based on the presence of colon polyps or genetic test results (n=16), or a family history of JP (n=6). Forty-eight percent (15/31, identified at 26–59 years) had extensive gastric polyposis (often described as “carpeted” or “innumerable”), 19% (6/31, identified at 17–63 years) had one to ten gastric polyps of variable histology, and 32% (10/31) had no gastric polyps identified. Small bowel polyps were identified in 39% (11/28, range 1–10, identified at 28–52 years) and were duodenal in eight individuals, duodenal and jejunal in one individual, and the sites were not specified for two individuals. One individual had diffuse jejunal thickening at age 58.

Malignancies were reported in eight individuals and included three colorectal cancers (diagnosed at ages 22, 30, and 38), two Hurthle cell thyroid tumors (ages 21 and 42), one individual with bilateral metachronous malignant ovarian teratomas (ages 19 and 38), one individual with lymphoma (age 55) and jejunal cancer (age 65), one adenocarcinoma of the esophagus arising in a region of Barrett esophagus (age 39); one mucinous neoplasm with low-grade dysplasia in the pancreatic head was reported (age not provided). The only malignancies that led to a diagnosis and subsequent screening were the three colorectal cancers. The jejunal cancer was found due to new symptoms in an individual who was already receiving colon screening. The remaining malignancies appear to have been identified incidentally. Additionally, 15 individuals had documented surgical procedures, including ten with some type of colectomy or colon resection (two for cancer, seven for polyposis, and one for polyposis and Crohn’s disease) and seven with gastrectomy due to either extensive polyposis or the presence of very large polyps. Gastric screening was frequently initiated due to new symptoms or family history information in individuals already receiving early colon screening.

Features associated with HHT were documented in 76% of individuals and included: epistaxis (19/31; 61%, all deemed abnormal in childhood), mucocutaneous telangiectases (15/31; 48%, identified at 5–65 years), liver AVM (6/16; 38%, identified at 21–52 years), brain AVM (1/26; 4%, identified at age 52), pulmonary AVM (9/17; 53%, identified at birth to 52 years), and intrapulmonary shunting on bubble echocardiogram (14/23; 61%, identified at 5–59 years). Eight of the nine individuals under the age of 21 had some screening for HHT features (2 of these had only brain MRI while the remaining had brain MRI and echocardiogram/chest CT), and 63% (5/8) had HHT features. GI bleeding was documented for 83% of the individuals with iron deficiency (20/24). All of these individuals had known GI polyps so it is unclear if the anemia was due to polyps or bleeding from telangiectases. Additionally, 50% (17/34), five of whom had no detectable visceral AVMs by CT or intrapulmonary shunting, were noted to have migraines (n=9), exercise intolerance (n=6), and/or digital clubbing (n=3), symptoms frequently found in patients with HHT.

DISCUSSION

The clinical manifestations of JP were present in this cohort of SMAD4 mutation carriers, the largest to date, with frequencies and characteristics that are quite consistent with published literature.¹ Colonic polyps were present in 97% of individuals who had undergone colonoscopy; the one individual with no colonic polyps detected was seven years old at the time of the last colonoscopy. As expected, gastric and small bowel polyps were less frequent than colonic polyps. However, we observed extensive gastric polyposis in 48% of individuals who had this screening which is consistent with previous studies showing that extensive gastric polyposis is more common with SMAD4 mutations compared to BMPR1A mutations.^29–31 HHT symptoms were also observed at rates that are near expected frequencies for individuals with HHT, although some individuals may not have met Curacao criteria for a clinical diagnosis.^6,7 Epistaxis and mucocutaneous telangiectases in particular were documented somewhat less frequently in this cohort than is typical for HHT patients, 61% and 48% respectively. This could certainly be due in part to age-related penetrance, as nine of the individuals who were assessed for these symptoms were younger than age 21 or because the patients were under the care of physicians who were focused on JP rather than HHT.

Previous studies of SMAD4 mutation carriers are consistent with the results of this study in that features of JP and HHT are regularly present. In 2004, Gallione et al. tested 14 patients from seven families with features of both JP and HHT for mutations in the ENG, ACVRL1, and SMAD4 genes.⁷ Mutations were identified in SMAD4 in all 14 patients. The SMAD4 mutations cosegregated with the JP-HHT phenotype. A subsequent case series, in 2010, describing the clinical features of JP-HHT included 19 patients, 15 of whom had identifiable SMAD4 mutations. ⁹ All 15 SMAD4 mutation carriers exhibited features of both JP and HHT, the most frequent being juvenile polyps (15/15), pulmonary AVMs (13/15), epistaxis (13/15), telangiectases (10/15), and anemia (9/15). The most recent series, by O’Malley et al., reports SMAD4 mutations in 21 individuals from 9 families who had a diagnosis of JP. Seventeen of these individuals underwent HHT screening; 94% (n=16) of these fit clinical criteria for HHT and 6% (n=1) had a suspected diagnosis.¹³

The rate of malignant neoplasms in our cohort was 24%, which is lower than previous reports and may be due to the young ages of some individuals as well as more frequent screening or prophylactic surgery, such as colectomy and gastrectomy. Five individuals had neoplasms previously reported in association with SMAD4 mutations (three colorectal, one jejunal, and one pancreatic). The one patient with esophageal adenocarcinoma also had Barrett’s esophagus, the major risk factor for this type of cancer.³² To our knowledge, germline SMAD4 mutations have not previously been reported in association with Hurthle cell thyroid tumors, ovarian teratomas, or lymphomas. However, acquired changes in SMAD4 expression and the TGF-β pathway have been implicated in tumorigenesis and/or progression in papillary thyroid carcinoma, ovarian carcinoma, and some lymphomas.^33–38 Somatic mutations and loss of heterozygosity have also been frequently found in breast cancers and one recent study reported intronic germline SMAD4 variants in BRCA1/2 negative breast cancer patients.³⁹ Larger studies are needed to determine if additional cancer risks may be present for SMAD4 mutation carriers.

Connective tissue findings have recently been reported in three families with SMAD4 mutations as well as a few individuals from a JP cohort.^{23,24, 31} These include mitral valve prolapse, aortic root dilatation, thoracic aortic dissections, and some skeletal features suggestive of Marfan syndrome. There have also been rare reports of individuals with HHT and large aortic aneurysms^40,41 and a genetic mutation (in ACVRL1) was reported for only one of them.⁴⁰ Seven of the 34 individuals in the current study (21%), from five separate families, had documented evidence of connective tissue findings with some features overlapping those of previous reports. In addition, our results include reports of a retinal detachment, brain aneurysms (in the absence of cerebral AVMs), and lax skin and joints, which have not been reported previously.

All of the genes associated with HHT (ENG, ACVRL1, and SMAD4) are part of the TGF-β signaling pathway which is essential for vascular integrity and angiogenic remodeling.⁴² Additionally, SMAD4 has the distinction of also acting as a tumor suppressor, which explains the JP phenotype.⁴³ While the newly reported connective tissue findings have not classically been considered to be manifestations of JP-HHT, perturbations of the TGF-β pathway due to mutations in other genes, such as FBN1, TGFBR1, TGFBR2, TGFBR, SMAD3, MYH11, and ACTA2, are well-described causes of several connective tissue disorders, such as Marfan syndrome, familial thoracic aortic aneurysms and aortic dissections, and Loeys-Dietz syndrome. ^44,45 Therefore, there is biological plausibility for observing these additional connective tissue findings, and further studies are needed to more formally assess for these risks in SMAD4 mutation carriers.

The findings from this study strengthen the argument that all SMAD4 mutation carriers should be screened following both JP and HHT protocols and that echocardiography, which is already employed with injected saline to screen for pulmonary AVMs, is doubly beneficial to assess for enlarged aortic roots.^9,13 Patients with Loeys-Dietz syndrome and other TGF-β associated connective tissue disorders are now treated with angiotensin receptor blockers (ARBs) for primary prevention of vascular complications. Although mechanistically attractive, no empiric data supports the use of ARBs in SMAD4 mutation carriers. More rigorously conducted studies are needed to quantify the risks, the possible benefits of screening, and efficacy of ARBs and other therapies. Finally, these results underscore the importance of appreciating the impact of a patient’s age in assessing phenotype. Age-related penetrance is a well-documented phenomenon associated with HHT features. While colonic polyps can frequently be found in the first decade of life, there is a wide range of onset, and additional studies are needed to better determine the range of onset for gastric and small bowel polyps.

The individuals in this study were ascertained based on SMAD4 carrier status, as opposed to a clinical diagnosis of JP and/or HHT, and the majority of them had screening for manifestations of both conditions. However, this study is still limited by a relatively small sample size, the young ages of some individuals, and incomplete screening for all findings of interest in some individuals. In particular, connective tissue findings may not have been appreciated or documented adequately in the medical records due to a lack of clinical suspicion, so we consider the proportion manifesting those findings as the lowest possible estimate for prevalence in JP-HHT.

CONCLUSION

This multi-center retrospective chart review of 34 individuals with SMAD4 mutations associated with JP-HHT provides additional documentation of the clinical phenotypic spectrum associated with these mutations. Regardless of initial clinical presentation, the majority of individuals had clinical features of both JP and HHT. Findings typically associated with TGF-β connective tissue disorders were observed in 21% of individuals with SMAD4 mutations. Complete JP and HHT clinical screening is recommended for all patients with SMAD4 mutations and clinicians should have a high suspicion for aortic root dilatation, thoracic aortic aneurysms, or other connective tissue pathology in these patients.