Costello syndrome with acoustic neuroma and cataract. Is the Costello locus linked to neurofibromatosis type 2 on 22q?

Costello syndrome: Clinical phenotype, genotype, and management guidelines

Costello syndrome (CS) is a RASopathy caused by activating germline mutations in HRAS. Due to ubiquitous HRAS gene expression, CS affects multiple organ systems and individuals are predisposed to cancer. Individuals with CS may have distinctive craniofacial features, cardiac anomalies, growth and developmental delays, as well as dermatological, orthopedic, ocular, and neurological issues; however, considerable overlap with other RASopathies exists. Medical evaluation requires an understanding of the multifaceted phenotype. Subspecialists may have limited experience in caring for these individuals because of the rarity of CS. Furthermore, the phenotypic presentation may vary with the underlying genotype. These guidelines were developed by an interdisciplinary team of experts in order to encourage timely health care practices and provide medical management guidelines for the primary and specialty care provider, as well as for the families and affected individuals across their lifespan. These guidelines are based on expert opinion and do not represent evidence-based guidelines due to the lack of data for this rare condition.

Retinal dystrophy in two boys with Costello syndrome due to the HRAS p.Gly13Cys mutation

Features of Costello Syndrome, a systemic disorder caused by germline mutations in the proto-oncogene HRAS from the RAS/MAPK pathway, include failure-to-thrive, short stature, coarse facial features, cardiac defects including hypertrophic cardiomyopathy, intellectual disability, and predisposition to neoplasia. Two unrelated boys with Costello syndrome and an HRAS mutation (p.Gly13Cys) are presented with their ophthalmologic findings. Both had early symptoms of nystagmus, photophobia, and vision abnormalities. Fundus examination findings of retinal dystrophy were present at age 3 years. Both boys have abnormal electroretinograms with reduced or undetectable rod responses along with reduced cone responses consistent with rod-cone dystrophy. Our observations suggest that early ophthalmic examination and re-evaluations are indicated in children with Costello syndrome.

Genotype-phenotype correlation in Costello syndrome: HRAS mutation analysis in 43 cases

BACKGROUND

Costello syndrome (CS) is a rare multiple congenital abnormality syndrome, associated with failure to thrive and developmental delay. One of the more distinctive features in childhood is the development of facial warts, often nasolabial and in other moist body surfaces. Individuals with CS have an increased risk of malignancy, suggested to be about 17%. Recently, mutations in the HRAS gene on chromosome 11p13.3 have been found to cause CS.

METHODS

We report here the results of HRAS analysis in 43 individuals with a clinical diagnosis of CS.

RESULTS

Mutations were found in 37 (86%) of patients. Analysis of parental DNA samples was possible in 16 cases for both parents and in three cases for one parent, and confirmed the mutations as de novo in all of these cases. Three novel mutations (G12C, G12E, and K117R) were found in five cases.

CONCLUSIONS

These results confirm that CS is caused, in most cases, by heterozygous missense mutations in the proto-oncogene HRAS. Analysis of the major phenotypic features by mutation suggests a potential correlation between malignancy risk and genotype, which is highest for patients with an uncommon (G12A) substitution. These results confirm that mutation testing for HRAS is a reliable diagnostic test for CS.

The adult phenotype in Costello syndrome

We report clinical findings in 17 adults with Costello syndrome ranging in age from 16 to 40 years. Two patients in this series have had bladder carcinoma, the only malignancy reported to affect adults with Costello syndrome. Benign tumors included multiple ductal papillomata in two women, and a fourth ventricle mass in one man, thought to be a choroid plexus papilloma. Endocrine problems in this series were osteoporosis, central hypogonadism, and delayed puberty. Other health problems were symptomatic Chiari malformations in three patients. Four patients had adult-onset gastro-esophageal reflux, three of whom had Chiari malformations. Fourteen adults had mild to moderate intellectual disability with three individuals having severe intellectual disability; 15 individuals attained some reading and writing skills and 14 showed ongoing acquisition of new skills into adulthood. On the basis of this data, we recommend that neuro-imaging be considered in adults with Costello syndrome if they develop symptoms suggestive of a Chiari malformation. In the event of pubertal delay, endocrine investigations are indicated and hormone treatment may be required. Bone density assessments should be performed in adults with Costello syndrome, particularly in those with pubertal abnormalities. Screening for microscopic hematuria as a marker for bladder carcinoma may be indicated, although this requires further evaluation.

Tumor predisposition in Costello syndrome

Costello syndrome (CS) is a rare congenital anomaly syndrome. Although it may be classified as an "overgrowth" syndrome due to slightly increased birth weight and relative macrocephaly, it is characterized by severe postnatal failure to thrive and short stature. Patients with CS have an increased risk for malignant tumors, a hallmark of several model overgrowth syndromes. The most common tumor in CS is rhabdomyosarcoma (RMS), followed by neuroblastoma and bladder carcinoma. The occurrence of bladder carcinoma in adolescents is distinctly unusual as this is typically a neoplasm of older adults and is not seen with increased frequency in other tumor predisposition syndromes. The increased tumor frequency in CS led to the proposal of a screening protocol, consisting of abdominal and pelvic ultrasounds, and urine studies for catecholamine metabolites and hematuria. It has since become apparent that patients with CS have an increased excretion of catecholamine metabolites in urine without the presence of an identifiable catecholamine secreting tumor. Thus, the urine assay for catecholamines is unhelpful as a screening test for neuroblastoma and should not be used in this population. The benefit of abdominal and pelvic ultrasound and urinalysis for hematuria as screening tests remains to be shown. A timely diagnosis of CS is a necessary prerequisite for awareness of the increased tumor risk. Once a malignancy has been identified, treatment should follow standard protocols. Additional medical problems characteristic for CS, such as hypertrophic cardiomyopathy and arrhythmia, need to be considered and addressed appropriately.

Disruption of the PDGFB gene in a 1;22 translocation patient does not cause Costello syndrome

We studied a female patient initially diagnosed with Costello syndrome who carries an apparently balanced translocation, t(1;22) (q24.3;q13.1). Molecular characterization of the translocation revealed a mosaic of two derivative chromosomes 1 in her peripheral blood lymphocytes, in one of which the coding region of the platelet-derived growth factor (PDGFB; chromosome 22q13.1) gene was disrupted. Both the initial translocation and the secondary intrachromosomal rearrangement appear to have occurred by nonhomologous (illegitimate) recombination. In 18 patients with Costello syndrome, mutation analysis of the genes belonging to the PDGF/R family, PDGFA, PDGFB, PDGFC, PDGFD, PDGFRA, and PDGFRB, revealed no pathogenic mutations. Reevaluation of the clinical symptoms of the translocation patient challenges the diagnosis of Costello syndrome in this patient. In total RNA isolated from lymphocytes of the translocation patient, we identified four different fusion transcripts consisting of PDGFB exons and parts of chromosome 1q24.3. In two of the mRNAs, exon 6 of PDGFB, encoding the 41 C-terminal amino acid residues, was absent. Immunofluorescence analysis showed that the wild-type protein was dispersed and formed a network-like structure in the extracellular matrix, whereas the two aberrant PDGFB proteins were localized in aggregates. We speculate that the biological consequences of the mutant PDGFB allele contributed to the unique disease phenotype of the translocation patient.

Costello syndrome and neurological abnormalities

Costello syndrome is a rare but increasingly recognized syndrome of unknown etiology. Neurological abnormalities are not rare in this syndrome and consist of structural and electrophysiological disorders. Ventricular dilatation is observed in more than 40% of cases. Other reported cerebral anomalies are brain atrophy, Chiari malformation and syringomyelia. Although there is insufficient data to propose strict guidelines, it seams reasonnable to have a low threshold for neuroimaging, in general, and particularly when neurologic signs or symptoms are present. Screening including cerebral MRI and EEG should be proposed after a diagnosis of Costello syndrome. The frequency of testing in such children should be guided by neurological follow-up.

Costello syndrome and Chiari I malformation: apropos of a case with a review of the literature regarding a potential association

We report a child with Costello syndrome and Chiari I malformation. The medical literature has several case reports of findings peculiar for each of these two clinical entities that, when investigated, can actually be found in both processes. Recent reports have shown additional medical coincidences for the Chiari I malformation, which, unlike the Chiari II malformation, was once thought not to have many additional associations. We propose that both Costello syndrome and other clinical entities that have potential mesodermal or ectodermal deficiencies (eg, Chiari I malformation and phakomatoses, respectively) could have common dysgeneses. Further case reports from other institutions regarding Costello syndrome and Chiari I malformation are now necessary to confirm our findings. Our hope is that these data will potentially add to our knowledge of the etiology of both Costello syndrome and Chiari I malformation and potentially aid in the definition of a genetic locus for both entities.

Further delineation of the behavioral and neurologic features in Costello syndrome

To describe clinical and neurodevelopmental phenotypes of Costello syndrome, we performed a retrospective review of the clinical records and findings in 10 children with Costello syndrome. All patients showed significant postnatal growth retardation and severe feeding difficulties leading to failure to thrive from early infancy. All required tube feeding and some needed high-calorie formulas for variable periods. Developmental quotients/IQs in seven children were 50 or less, and three were in the mildly retarded range. Five had seizures. Remarkable manifestations not previously reported were the characteristic behavior in infancy. Although happy and sociable personality was always emphasized in the genetic literature, all children showed significant irritability, including hypersensitivity to sound and tactile stimuli, sleep disturbance, and excess shyness with strangers in infancy. Those symptoms usually disappeared around age 2-4 years. Other clinical signs included cardiac abnormalities (8), musculoskeletal abnormalities (10), ophthalmological manifestations (5), increased urinary vanillymandelic acid (VMA) and homovanillic acid (HVA) (3), rhabdomyosarcoma (1), laryngomalacia (1), and cryptorchidism (1). Only three girls had papillomata. Family histories were negative for Costello syndrome. In conclusion, we confirm the wide spectrum of mental function in patients with Costello syndrome, which ranges from severe to mild. During infancy Costello syndrome showed remarkable irritability with severe feeding problems, which attributes significant difficulties to the parents of affected children.

Costello syndrome: an overview

The Costello syndrome is characterized by prenatally increased growth, postnatal growth retardation, coarse face, loose skin resembling cutis laxa, nonprogressive cardiomyopathy, developmental delay, and a outgoing, friendly behavior. Patients can develop papillomata, especially around the mouth, and have a predisposition for malignancies (mainly abdominal and pelvic rhabdomyosarcoma in childhood). Costello syndrome is likely to be an autosomal dominant disorder. The pathogenesis is unclear, but there are many clues for a disturbed elastogenesis, possibly through a disturbed elastin-binding protein reuse by chondroitin sulfate-bearing proteoglycans accumulation. A review of the findings in the 73 patients that have been described in sufficient detail is provided.

[Costello syndrome: clinical aspects and tumor risk]

Costello syndrome is a sporadic development anomaly suggesting a genetic determinism. Main features include characteristic facial features, mental retardation, growth retardation, cutis laxa, heart malformation, and peri-orificial papillomata. In previous reported cases, the frequency of tumors is 15%, which argues for a screening protocol. The occurrence of a tumor in a child with growth retardation and cutis laxa must be reminiscent of Costello syndrome. The determinism of this syndrome is still unknown, and the hypothesis of an inactivation of a tumor suppressor gene is to be considered.

Further delineation of cardiac abnormalities in Costello syndrome

We review the cardiac abnormalities in 94 patients (27 new, 67 literature) with Costello syndrome, an increasingly recognized syndrome consisting of increased birth weight, postnatal growth retardation, and distinctive facial, skin, and musculoskeletal features (MIM 218040). A cardiac abnormality was found in 59 (63%) patients, with each of three categories occurring in approximately one-third of patients. A cardiovascular malformation (CVM) was noted in 30%, typically pulmonic stenosis (46% of those with a CVM). Cardiac hypertrophy was reported in 34%, which involved the left ventricle in 50% and was usually consistent with classic hypertrophic cardiomyopathy (HCM). A variety of rhythm disturbances were reported in 33%. Most (74%) were atrial tachycardia that was reported as supraventricular, chaotic, multifocal, or ectopic. Of 31 patients with a rhythm abnormality, 22 (68%) had an additional abnormality, i.e., CVM (4), cardiac hypertrophy (12), or both (6). Nine patients had isolated dysrhythmia, five (56%) of whom died. All of the 12 (13%) patients who died had a cardiac abnormality. One patient died of embryonal rhabdomyosarcoma, but in the remainder, a cardiac cause of death could not be disproved. All patients with Costello syndrome need a baseline cardiology evaluation with echocardiography and Holter monitoring. Additional prospective evaluations, even in patients without apparent cardiac abnormalities, would be prudent, although data are insufficient to propose a specific schedule.

Five additional Costello syndrome patients with rhabdomyosarcoma: proposal for a tumor screening protocol

We report five new cases of rhabdomyosarcoma (RMS) in Costello syndrome. These cases, combined with those previously reported, increase the number of solid tumors to 17 (10 RMSs, 3 neuroblastomas, 2 bladder carcinomas, 1 vestibular schwannoma, 1 epithelioma), in at least 100 known Costello syndrome patients. Despite possible ascertainment bias, and the incomplete identification of all Costello syndrome patients, the tumor frequency could be as high as 17%. This is comparable to the 7-21% frequency of solid tumors in Beckwith-Wiedemann syndrome (BWS), and may justify tumor screening. Based on the recommendations for screening BWS patients, we propose a screening protocol consisting of ultrasound examination of the abdomen and pelvis every 3-6 months until age 8-10 years for RMS and abdominal neuroblastoma; urine catecholamine metabolite analysis every 6-12 months until age 5 years for neuroblastoma; and urinalysis for hematuria annually for bladder carcinoma after age 10 years. These recommendations may need to be modified, as new information becomes available. Potential criticism of the tumor screening protocol concerns the lack of evidence for improved outcome, and possible overestimation of the tumor risk. The ability of RMSs to occur at various sites complicates tumor screening, but 8 of the 10 RMSs in Costello syndrome patients originated from the abdomen, pelvis and urogenital area. Prior diagnosis of Costello syndrome is a prerequisite for the implementation of any screening protocol. The diagnosis of Costello syndrome should also be considered in individuals with RMS and physical findings suggestive of Costello syndrome.

Decreased elastin deposition and high proliferation of fibroblasts from Costello syndrome are related to functional deficiency in the 67-kD elastin-binding protein

Costello syndrome is characterized by mental retardation, loose skin, coarse face, skeletal deformations, cardiomyopathy, and predisposition to numerous malignancies. The genetic origin of Costello syndrome has not yet been defined. Using immunohistochemistry and metabolic labeling with [3H]-valine, we have established that cultured skin fibroblasts obtained from patients with Costello syndrome did not assemble elastic fibers, despite an adequate synthesis of tropoelastin and normal deposition of the microfibrillar scaffold. We found that impaired production of elastic fibers by these fibroblasts is associated with a functional deficiency of the 67-kD elastin-binding protein (EBP), which is normally required to chaperone tropoelastin through the secretory pathways and to its extracellular assembly. Metabolic pulse labeling of the 67-kD EBP with radioactive serine and further chase of this tracer indicated that both normal fibroblasts and fibroblasts from patients with Costello syndrome initially synthesized comparable amounts of this protein; however, the fibroblasts from Costello syndrome patients quickly lost it into the conditioned media. Because the normal association between EBP and tropoelastin can be disrupted on contact with galactosugar-bearing moieties, and the fibroblasts from patients with Costello syndrome revealed an unusual accumulation of chondroitin sulfate-bearing proteoglycans (CD44 and biglycan), we postulate that a chondroitin sulfate may be responsible for shedding EBP from Costello cells and in turn for their impaired elastogenesis. This was further supported by the fact that exposure to chondroitinase ABC, an enzyme capable of chondroitin sulfate degradation, restored normal production of elastic fibers by fibroblasts from patients with Costello syndrome. We also present evidence that loss of EBP from fibroblasts of Costello syndrome patients is associated with an unusually high rate of cellular proliferation.

Costello syndrome: report and review

We describe a 34-year-old woman with mental retardation, short stature, macrocephaly, a "coarse" face, hoarse voice, and redundant skin with deep palmar and plantar creases who had evident Costello syndrome. Lacking papillomata, she had wart-like lesions of the skin. The previously reported patients with Costello syndrome are reviewed. Costello syndrome is probably an autosomal dominant disorder, either caused by a mutation in a single gene or by microdeletion.