Pharmacodynamic Study of Miransertib in Individuals with Proteus Syndrome.

Proteus syndrome is a life-threatening segmental overgrowth syndrome caused by a mosaic gain-of-function AKT1 variant. There are no effective treatments for Proteus syndrome. Miransertib is an AKT1 inhibitor that, prior to this study, has been evaluated only in adult oncology trials. We designed a non-randomized, phase 0/1 pilot study of miransertib in adults and children with Proteus syndrome to identify an appropriate dosage starting point for a future efficacy trial using a pharmacodynamic endpoint. The primary endpoint was a 50% reduction in the tissue levels of AKT phosphorylation from biopsies in affected individuals. We also evaluated secondary efficacy endpoints. We found that a dose of 5 mg/m2/day (1/7 the typical dose used in oncology) led to a 50% reduction in phosphorylated AKT (pAKT) in affected tissues from five of six individuals. This dose was well tolerated. Two of the six efficacy endpoints (secondary objectives) suggested that this agent may be efficacious. We observed a decrease in a cerebriform connective tissue nevus and a reduction in pain in children. We conclude that 5 mg/m2/day of miransertib is an appropriate starting point for future efficacy trials and that this agent shows promise of therapeutic efficacy in children with Proteus syndrome.

Missense Variants in the Histone Acetyltransferase Complex Component Gene TRRAP Cause Autism and Syndromic Intellectual Disability.

Acetylation of the lysine residues in histones and other DNA-binding proteins plays a major role in regulation of eukaryotic gene expression. This process is controlled by histone acetyltransferases (HATs/KATs) found in multiprotein complexes that are recruited to chromatin by the scaffolding subunit transformation/transcription domain-associated protein (TRRAP). TRRAP is evolutionarily conserved and is among the top five genes intolerant to missense variation. Through an international collaboration, 17 distinct de novo or apparently de novo variants were identified in TRRAP in 24 individuals. A strong genotype-phenotype correlation was observed with two distinct clinical spectra. The first is a complex, multi-systemic syndrome associated with various malformations of the brain, heart, kidneys, and genitourinary system and characterized by a wide range of intellectual functioning; a number of affected individuals have intellectual disability (ID) and markedly impaired basic life functions. Individuals with this phenotype had missense variants clustering around the c.3127G>A p.(Ala1043Thr) variant identified in five individuals. The second spectrum manifested with autism spectrum disorder (ASD) and/or ID and epilepsy. Facial dysmorphism was seen in both groups and included upslanted palpebral fissures, epicanthus, telecanthus, a wide nasal bridge and ridge, a broad and smooth philtrum, and a thin upper lip. RNA sequencing analysis of skin fibroblasts derived from affected individuals skin fibroblasts showed significant changes in the expression of several genes implicated in neuronal function and ion transport. Thus, we describe here the clinical spectrum associated with TRRAP pathogenic missense variants, and we suggest a genotype-phenotype correlation useful for clinical evaluation of the pathogenicity of the variants.

Genomic tools for health: Secondary findings as findings to be shared.

PURPOSE: Whether and how to disclose secondary finding (SF) information to children is ethically debated. Some argue that genetic testing of minors should be limited to preserve the child's future autonomy. Others suggest that disclosure of SFs can occur if it is in the best interests of the child. However, the ways that parents conceptualize and weigh their child's future autonomy against the interests of their child and other family members are unknown. METHODS: To explore how parents understand SF disclosure in the context of their child and other family members' lives, we conducted semistructured interviews with 30 families (40 parents in total). All parents had children who were enrolled in a genetic sequencing protocol that returned results by default. RESULTS: We found that parents did not routinely conceptualize SFs as distinctive health information. Rather parents saw this information as part of their child's overall health. To make decisions about disclosure, parents weighed their child's ability to understand the SF information and their other family member's need to know. CONCLUSION: Because most families desired SF information, we argue that disclosure of SF be reconceptualized to reflect the lived experiences of those who may receive this information.

Low-level variant calling for non-matched samples using a position-based and nucleotide-specific approach.

BACKGROUND: The widespread use of next-generation sequencing has identified an important role for somatic mosaicism in many diseases. However, detecting low-level mosaic variants from next-generation sequencing data remains challenging. RESULTS: Here, we present a method for Position-Based Variant Identification (PBVI) that uses empirically-derived distributions of alternate nucleotides from a control dataset. We modeled this approach on 11 segmental overgrowth genes. We show that this method improves detection of single nucleotide mosaic variants of 0.01-0.05 variant allele fraction compared to other low-level variant callers. At depths of 600 × and 1200 ×, we observed > 85% and > 95% sensitivity, respectively. In a cohort of 26 individuals with somatic overgrowth disorders PBVI showed improved signal to noise, identifying pathogenic variants in 17 individuals. CONCLUSION: PBVI can facilitate identification of low-level mosaic variants thus increasing the utility of next-generation sequencing data for research and diagnostic purposes.

Recurrent, Activating Variants in the Receptor Tyrosine Kinase DDR2 Cause Warburg-Cinotti Syndrome.

We have investigated a distinct disorder with progressive corneal neovascularization, keloid formation, chronic skin ulcers, wasting of subcutaneous tissue, flexion contractures of the fingers, and acro-osteolysis. In six affected individuals from four families, we found one of two recurrent variants in discoidin domain receptor tyrosine kinase 2 (DDR2): c.1829T>C (p.Leu610Pro) or c.2219A>G (p.Tyr740Cys). DDR2 encodes a collagen-responsive receptor tyrosine kinase that regulates connective-tissue formation. In three of the families, affected individuals comprise singleton adult individuals, and parental samples were not available for verification of the de novo occurrence of the DDR2 variants. In the fourth family, a mother and two of her children were affected, and the c.2219A>G missense variant was proven to be de novo in the mother. Phosphorylation of DDR2 was increased in fibroblasts from affected individuals, suggesting reduced receptor autoinhibition and ligand-independent kinase activation. Evidence for activation of other growth-regulatory signaling pathways was not found. Finally, we found that the protein kinase inhibitor dasatinib prevented DDR2 autophosphorylation in fibroblasts, suggesting an approach to treatment. We propose this progressive, fibrotic condition should be designated as Warburg-Cinotti syndrome.

Evaluation of Recipients of Positive and Negative Secondary Findings Evaluations in a Hybrid CLIA-Research Sequencing Pilot.

While consensus regarding the return of secondary genomic findings in the clinical setting has been reached, debate about such findings in the research setting remains. We developed a hybrid, research-clinical translational genomics process for research exome data coupled with a CLIA-validated secondary findings analysis. Eleven intramural investigators from ten institutes at the National Institutes of Health piloted this process. Nearly 1,200 individuals were sequenced and 14 secondary findings were identified in 18 participants. Positive secondary findings were returned by a genetic counselor following a standardized protocol, including referrals for specialty follow-up care for the secondary finding local to the participants. Interviews were undertaken with 13 participants 4 months after receipt of a positive report. These participants reported minimal psychologic distress within a process to assimilate their results. Of the 13, 9 reported accessing the recommended health care services. A sample of 107 participants who received a negative findings report were surveyed 4 months after receiving it. They demonstrated good understanding of the negative secondary findings result and most expressed reassurance (64%) from that report. However, a notable minority (up to 17%) expressed confusion regarding the distinction of primary from secondary findings. This pilot shows it is feasible to couple CLIA-compliant secondary findings to research sequencing with minimal harms. Participants managed the surprise of a secondary finding with most following recommended follow up, yet some with negative findings conflated secondary and primary findings. Additional work is needed to understand barriers to follow-up care and help participants distinguish secondary from primary findings.

A systematic literature review of disclosure practices and reported outcomes for medically actionable genomic secondary findings.

PURPOSE: Secondary findings (SFs) are present in 1-4% of individuals undergoing genome/exome sequencing. A review of how SFs are disclosed and what outcomes result from their receipt is urgent and timely. METHODS: We conducted a systematic literature review of SF disclosure practices and outcomes after receipt including cascade testing, family and provider communication, and health-care actions. Of the 1,184 nonduplicate records screened we summarize findings from 27 included research articles describing SF disclosure practices, outcomes after receipt, or both. RESULTS: The included articles reported 709 unique SF index recipients/families. Referrals and/or recommendations were provided 647 SF recipients and outcome data were available for 236. At least one recommended evaluation was reported for 146 SF recipients; 16 reports of treatment or prophylactic surgery were identified. We found substantial variations in how the constructs of interest were defined and described. CONCLUSION: Variation in how SF disclosure and outcomes were described limited our ability to compare findings. We conclude the literature provided limited insight into how the American College of Medical Genetics and Genomics (ACMG) guidelines have been translated into precision health outcomes for SF recipients. Robust studies of SF recipients are needed and should be prioritized for future research.

Hypertrichotic patches as a mosaic manifestation of Proteus syndrome.

BACKGROUND: Proteus syndrome is an overgrowth disorder caused by a mosaic activating AKT1 variant. Hair abnormalities in Proteus syndrome have rarely been reported, and frequencies of such findings have not been elucidated. OBJECTIVE: To define the types and frequencies of hair findings in individuals with Proteus syndrome. METHODS: A cross-sectional study was conducted of individuals with clinical features of Proteus syndrome and a confirmed pathogenic variant in AKT1 evaluated between November 1996 and June 2019 at the National Institutes of Health Clinical Center. Medical records were reviewed for patterning, density, and color of hair on the body and scalp. RESULTS: Of 45 individuals evaluated, 29 (64%) had asymmetric hypertrichosis on the body. This included unilateral blaschkoid hypertrichotic patches overlying normal skin or epidermal nevi in 16 (36%), unilateral nonblaschkoid hypertrichotic patches in 11 (24%), and unilateral limb hypertrichosis in 10 (22%). Diffuse, scattered, or patchy changes in scalp hair density or color were present in 11 individuals (24%). LIMITATIONS: The retrospective, observational design, and limited longitudinal follow-up. CONCLUSIONS: Asymmetric variations in hair distribution, thickness, length, and color contribute to the overall mosaic appearance of the skin in Proteus syndrome, an observation that provides novel insights into the role of phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) signaling in skin appendage development.

NAA10 polyadenylation signal variants cause syndromic microphthalmia.

BACKGROUND: A single variant in NAA10 (c.471+2T>A), the gene encoding N-acetyltransferase 10, has been associated with Lenz microphthalmia syndrome. In this study, we aimed to identify causative variants in families with syndromic X-linked microphthalmia. METHODS: Three families, including 15 affected individuals with syndromic X-linked microphthalmia, underwent analyses including linkage analysis, exome sequencing and targeted gene sequencing. The consequences of two identified variants in NAA10 were evaluated using quantitative PCR and RNAseq. RESULTS: Genetic linkage analysis in family 1 supported a candidate region on Xq27-q28, which included NAA10. Exome sequencing identified a hemizygous NAA10 polyadenylation signal (PAS) variant, chrX:153,195,397T>C, c.*43A>G, which segregated with the disease. Targeted sequencing of affected males from families 2 and 3 identified distinct NAA10 PAS variants, chrX:g.153,195,401T>C, c.*39A>G and chrX:g.153,195,400T>C, c.*40A>G. All three variants were absent from gnomAD. Quantitative PCR and RNAseq showed reduced NAA10 mRNA levels and abnormal 3' UTRs in affected individuals. Targeted sequencing of NAA10 in 376 additional affected individuals failed to identify variants in the PAS. CONCLUSION: These data show that PAS variants are the most common variant type in NAA10-associated syndromic microphthalmia, suggesting reduced RNA is the molecular mechanism by which these alterations cause microphthalmia/anophthalmia. We reviewed recognised variants in PAS associated with Mendelian disorders and identified only 23 others, indicating that NAA10 harbours more than 10% of all known PAS variants. We hypothesise that PAS in other genes harbour unrecognised pathogenic variants associated with Mendelian disorders. The systematic interrogation of PAS could improve genetic testing yields.

A dyadic genotype-phenotype approach to diagnostic criteria for Proteus syndrome.

Phenotype-based diagnostic criteria were developed for Proteus syndrome in 1999 and updated in 2006. Subsequently, the causative mosaic gene alteration was discovered, the c.49G>A p.E17K variant in AKT1. As well, a number of overlapping overgrowth disorders attributable to mosaic PIK3CA variants have now been characterized, leading to the designation of PIK3CA-related overgrowth spectrum (PROS). Finally, ongoing work to better characterize Proteus syndrome has led to identification of additional features of that disorder that could be useful in diagnostic criteria. We have taken the opportunity of these discoveries to re-evaluate the Proteus syndrome diagnostic criteria. Here we propose a new set of diagnostic criteria that establishes a weighted, point-based system for the phenotypic attributes and then integrates that with the potential molecular test results to result in one of two designations: AKT1-related Proteus syndrome or AKT1-related overgrowth spectrum. A patient whose only manifestation is an AKT1 c.49G>A-positive tumor would receive neither of these designations. Here we review the rational basis of diagnostic criteria and argue that a unitary diagnostic entity is a distinct gene-phenotype dyad and that this should be the model for all mendelian disorders. The gene-alone or phenotype-alone approach is inadequate to rigorously delineate a unitary diagnostic entity.

Thrombosis risk factors in PIK3CA-related overgrowth spectrum and Proteus syndrome.

Increased risk of thromboembolism has been recognized in individuals with mosaic overgrowth disorders, Proteus syndrome (PS) and PIK3CA-related overgrowth spectrum (PROS), including Klippel-Trenaunay syndrome and CLOVES syndrome. PS and PROS have distinct, yet overlapping clinical findings and are caused by somatic pathogenic variants in the PI3K/AKT gene signaling pathway. PS is caused by a single somatic activating AKT1 c.49G > A p.E17K variant while PROS can be caused one of multiple variants in PIK3CA. The role of prothrombotic factors, endothelial cell adhesion molecules, and vascular malformations in both PS and PROS have not been previously investigated. A pilot study of prospective clinical and laboratory evaluations with the purposes of identifying potential risk factors for thrombosis was conducted. Doppler ultrasounds and magnetic resonance angiogram/ venography (MRA/MRV) scans identified vascular malformations in PS and PROS that were not appreciated on physical examination. Abnormal D-dimers (0.60-2.0 mcg/ml) occurred in half of individuals, many having vascular malformations, but no thromboses. Soluble vascular endothelial markers, including thrombomodulin, soluble vascular adhesion molecule (sVCAM), soluble intercellular adhesion molecule (sICAM), E-selectin, and P-selectin were significantly higher in PS and PROS compared to controls. However, no single attribute was identified that explained the risk of thrombosis. Predisposition to thrombosis is likely multifactorial with risk factors including chronic stasis within vascular malformations, stasis from impaired mobility (e.g., following surgery), decreased anticoagulant proteins, and effects of AKT1 and PIK3CA variants on vascular endothelium. Based on our findings, we propose clinical recommendations for surveillance of thrombosis in PS and PROS.

GCM2-Activating Mutations in Familial Isolated Hyperparathyroidism.

Primary hyperparathyroidism (PHPT) is a common endocrine disease characterized by parathyroid hormone excess and hypercalcemia and caused by hypersecreting parathyroid glands. Familial PHPT occurs in an isolated nonsyndromal form, termed familial isolated hyperparathyroidism (FIHP), or as part of a syndrome, such as multiple endocrine neoplasia type 1 or hyperparathyroidism-jaw tumor syndrome. The specific genetic or other cause(s) of FIHP are unknown. We performed exome sequencing on germline DNA of eight index-case individuals from eight unrelated kindreds with FIHP. Selected rare variants were assessed for co-segregation in affected family members and screened for in an additional 32 kindreds with FIHP. In eight kindreds with FIHP, we identified three rare missense variants in GCM2, a gene encoding a transcription factor required for parathyroid development. Functional characterization of the GCM2 variants and deletion analyses revealed a small C-terminal conserved inhibitory domain (CCID) in GCM2. Two of the three rare variants were recurrent, located in the GCM2 CCID, and found in seven of the 40 (18%) kindreds with FIHP. These two rare variants acted as gain-of-function mutations that increased the transcriptional activity of GCM2, suggesting that GCM2 is a parathyroid proto-oncogene. Our results demonstrate that germline-activating mutations affecting the CCID of GCM2 can cause FIHP.

Safety and efficacy of low-dose sirolimus in the PIK3CA-related overgrowth spectrum.

PURPOSE: PIK3CA-related overgrowth spectrum (PROS) encompasses a range of debilitating conditions defined by asymmetric overgrowth caused by mosaic activating PIK3CA variants. PIK3CA encodes the p110α catalytic subunit of phosphatidylinositol-3-kinase (PI3K), a critical transducer of growth factor signaling. As mTOR mediates the growth-promoting actions of PI3K, we hypothesized that the mTOR inhibitor sirolimus would slow pathological overgrowth. METHODS: Thirty-nine participants with PROS and progressive overgrowth were enrolled into open-label studies across three centers, and results were pooled. For the primary outcome, tissue volumes at affected and unaffected sites were measured by dual energy X-ray absorptiometry during 26 weeks of untreated run-in and 26 weeks of sirolimus therapy. RESULTS: Thirty participants completed the study. Sirolimus led to a change in mean percentage total tissue volume of -7.2% (SD 16.0, p = 0.04) at affected sites, but not at unaffected sites (+1.7%, SD 11.5, p = 0.48) (n = 23 evaluable). Twenty-eight of 39 (72%) participants had ≥1 adverse event related to sirolimus of which 37% were grade 3 or 4 in severity and 7/39 (18%) participants were withdrawn consequently. CONCLUSION: This study suggests that low-dose sirolimus can modestly reduce overgrowth, but cautions that the side-effect profile is significant, mandating individualized risk-benefit evaluations for sirolimus treatment in PROS.

A Point Mutation in PDGFRB Causes Autosomal-Dominant Penttinen Syndrome.

Penttinen syndrome is a distinctive disorder characterized by a prematurely aged appearance with lipoatrophy, epidermal and dermal atrophy along with hypertrophic lesions that resemble scars, thin hair, proptosis, underdeveloped cheekbones, and marked acro-osteolysis. All individuals have been simplex cases. Exome sequencing of an affected individual identified a de novo c.1994T>C p.Val665Ala variant in PDGFRB, which encodes the platelet-derived growth factor receptor ß. Three additional unrelated individuals with this condition were shown to have the identical variant in PDGFRB. Distinct mutations in PDGFRB have been shown to cause infantile myofibromatosis, idiopathic basal ganglia calcification, and an overgrowth disorder with dysmorphic facies and psychosis, none of which overlaps with the clinical findings in Penttinen syndrome. We evaluated the functional consequence of this causative variant on the PDGFRB signaling pathway by transfecting mutant and wild-type cDNA into HeLa cells, and transfection showed ligand-independent constitutive signaling through STAT3 and PLCγ. Penttinen syndrome is a clinically distinct genetic condition caused by a PDGFRB gain-of-function mutation that is associated with a specific and unusual perturbation of receptor function.

Urine cell-free DNA is a biomarker for nephroblastomatosis or Wilms tumor in PIK3CA-related overgrowth spectrum (PROS).

PURPOSE: We set out to facilitate the molecular diagnosis of patients with PIK3CA-related overgrowth spectrum (PROS), a heterogeneous somatic disorder characterized by variable presentations of segmental overgrowth, vascular malformations, skin lesions, and nephroblastomatosis, rare precursor lesions to Wilms tumor. Molecular diagnosis of PROS is challenging due to its mosaic nature, often requiring invasive biopsies. METHODS: Digital droplet polymerase chain reaction (ddPCR) was used to analyze tissues including urine, saliva, buccal cells, and blood, from eight patients with PROS. Further analyses were performed on plasma and urine cell-free DNA (cfDNA). RESULTS: PIK3CA variants were detected in plasma cfDNA at levels up to 0.5% in 50% of tested samples. In addition, high levels of PIK3CA variants in urine cfDNA correlated with a history of nephroblastomatosis compared with patients without renal involvement (P < 0.05). CONCLUSION: Digital droplet PCR is a sensitive molecular tool that enables low-level variant detection of PIK3CA in various tissue types, providing an alternative diagnostic method. Furthermore, urine cfDNA is a candidate biomarker for nephroblastomatosis in PROS, which may be useful to refine screening guidelines for tumor risk in these patients.

Autosomal recessive Noonan syndrome associated with biallelic LZTR1 variants.

PURPOSE: To characterize the molecular genetics of autosomal recessive Noonan syndrome. METHODS: Families underwent phenotyping for features of Noonan syndrome in children and their parents. Two multiplex families underwent linkage analysis. Exome, genome, or multigene panel sequencing was used to identify variants. The molecular consequences of observed splice variants were evaluated by reverse-transcription polymerase chain reaction. RESULTS: Twelve families with a total of 23 affected children with features of Noonan syndrome were evaluated. The phenotypic range included mildly affected patients, but it was lethal in some, with cardiac disease and leukemia. All of the parents were unaffected. Linkage analysis using a recessive model supported a candidate region in chromosome 22q11, which includes LZTR1, previously shown to harbor mutations in patients with Noonan syndrome inherited in a dominant pattern. Sequencing analyses of 21 live-born patients and a stillbirth identified biallelic pathogenic variants in LZTR1, including putative loss-of-function, missense, and canonical and noncanonical splicing variants in the affected children, with heterozygous, clinically unaffected parents and heterozygous or normal genotypes in unaffected siblings. CONCLUSION: These clinical and genetic data confirm the existence of a form of Noonan syndrome that is inherited in an autosomal recessive pattern and identify biallelic mutations in LZTR1.

Characterization of the hepatosplenic and portal venous findings in patients with Proteus syndrome.

Proteus syndrome (PS) is a rare disorder caused by a mosaic AKT1 variant that comprises patchy overgrowth of tissues derived from all three germinal layers affecting multiple viscera. We sought to delineate the extent of hepatoportal manifestations in patients with PS. We identified patients with PS who had abdominal imaging from 1989 to 2015 in a natural history study. Imaging was characterized for evidence of focal findings in the liver, spleen, and portal vasculature and for organomegaly. Relevant clinical and laboratory data were compared among those with or without organomegaly. Abdominal imaging was available on 38 patients including 20 who had serial studies. Nine patients had focal hepatic lesions including vascular malformations (VMs). Focal splenic abnormalities were noted in seven patients. Patients without cutaneous VMs did not have visceral VMs. Nine patients had splenomegaly, 12 had portal vein dilation, and 4 had hepatomegaly. There was a weak correlation of portal vein dilation to spleen height ratio (r2 = 0.18, p < .05). On laboratory evaluation, hepatic function was normal but there was thrombocytopenia in those with splenomegaly; platelet counts were 179 ± 87K/µL compared to those with normal spleen size at 253 ± 57K/µL (p < .05). Overall, focal hepatosplenic abnormalities occurred in 11 of 38 (29%) patients with PS. Splenomegaly and portal venous dilation were both found in 8 of 38 (21%) patients; however, other than relative thrombocytopenia, there was no evidence of portal hypertension. Although the AKT1-E17K somatic variant is a suspected oncogene, there were no malignant lesions identified in this study.

Orthopaedic Management of Leg-length Discrepancy in Proteus Syndrome: A Case Series.

INTRODUCTION: Proteus syndrome (PS) is a rare mosaic disorder comprising asymmetric bony and soft tissue overgrowth leading to significant morbidity. Placement of growth inhibition hardware with subsequent epiphyseal arrest improves leg-length and angular deformities in pediatric patients without PS. The purpose of this study was to review the surgical approach and present outcomes, complications, and recommendations in 8 patients with PS and leg-length discrepancy (LLD). METHODS: We conducted a retrospective chart review of 8 patients with PS whose primary reason for surgery was LLD. Patients were eligible if they met clinical diagnostic criteria for PS and if the National Institutes of Health team performed at least 1 of their surgical interventions between 2005 and 2015. Surgical techniques included growth inhibition, with tension band plates, applied ≥1 times, and epiphyseal arrest. RESULTS: Eight patients, followed for an average of 4.6 years (range, 1.0 to 7.1 y) after the index procedure, were included in this analysis. Average age at first LLD surgery was 9.4 years (range, 6.1 to 13.6 y); the average LLD was 3.4 cm (range, 0.4 to 7.0 cm) at presentation, and 5.0 cm (range, 1.8 to 10.0 cm) at the time of the first LLD surgery. Participants underwent 23 total surgeries (range, 1 to 5 per patient) and 7 patients have completed surgical intervention. For the 7 patients who did not require overcorrection the average LLD at the last clinical encounter was 2.6 cm (range, 0.6 to 7.2 cm). We encountered 2 complications: 2 patients developed mild knee valgus, which responded to standard guided growth techniques. CONCLUSIONS: This case series suggests that growth inhibition and epiphyseal arrest in children with PS can reduce LLD with few complications. Careful monitoring, rapid mobilization, deep venous thrombosis prophylaxis, and sequential compression devices were also integral elements of our surgical protocol. LEVEL OF EVIDENCE: Level IV.

Quantifying survival in patients with Proteus syndrome.

PurposeProteus syndrome is a rare mosaic overgrowth disorder that is associated with severe complications. While anecdotal data have suggested that the life span of affected patients is reduced, this has not been measured. Mortality data on rare diseases is critical for assessing treatments and other interventions.MethodsTo address this we used the clinical research records of 64 patients in a longitudinal natural history cohort at the National Institutes of Health to ascertain the data in an organized manner and estimate survival using a Kaplan-Meier approach.ResultsThe median age of diagnosis was 19 months. Based on this analysis, there was 25% probability of death by 22 years of age. Ten of the 11 patients who died were younger than 22 years of age, and there was only a single death after this age.ConclusionThese data quantify the risk of premature death in Proteus syndrome, which can be used to support interventions and trials. Although the risk of death is substantial, the fact that only one patient died after 22 years of age supports anecdotal evidence that the disease process moderates after the end of adolescence. Interventions to reduce mortality should be targeted to the pediatric age range.

Characterization of thrombosis in patients with Proteus syndrome.

Patients with overgrowth and complex vascular malformation syndromes, including Proteus syndrome have an increased risk of thromboembolism. Proteus syndrome is a mosaic, progressive overgrowth disorder involving vasculature, skin, and skeleton, and caused by a somatic activating mutation in AKT1. We conducted a comprehensive review of the medical histories and hematologic evaluations of 57 patients with Proteus syndrome to identify potential risk factors for thrombosis. We found that six of ten patients, who were deceased, died secondary to deep venous thrombosis and/or pulmonary embolism. Of the remaining 47 living patients, six had thromboembolic events that all occurred postoperatively and in an affected limb. Eleven of 21 patients had an abnormal hypercoagulable panel including Factor V Leiden heterozygotes, antithrombin III deficiency, positive lupus anticoagulant, or Protein C or S deficiencies. We observed that eight of 17 patients had an abnormal D-dimer level >0.5 mcg/dl, but deep venous thromboses occurred in only four of those with D-dimer >1.0 mcg/dl. We conclude that the predisposition to thrombosis is likely to be multifaceted with risk factors including vascular malformations, immobility, surgery, additional prothrombotic factors, and possible pathophysiologic effects of the somatic AKT1 mutation on platelet function or the vascular endothelium. The D-dimer test is useful as a screen for thromboembolism, although the screening threshold may need to be adjusted for patients with this disorder. We propose developing a registry to collect D-dimer and outcome data to facilitate adjustment of the D-dimer threshold for Proteus syndrome and related disorders, including PIK3CA-Related Overgrowth Spectrum.