FDA approval summary for lonafarnib (Zokinvy) for the treatment of Hutchinson-Gilford progeria syndrome and processing-deficient progeroid laminopathies.

The U.S. Food and Drug Administration recently approved lonafarnib as the first treatment for Hutchinson-Gilford progeria syndrome (HGPS) and processing-deficient progeroid laminopathies. This approval was primarily based on a comparison of patients with HGPS treated with lonafarnib in 2 open-label trials with an untreated patient cohort. With up to 11 years of follow-up, it was found that the lonafarnib treated patients with HGPS had a survival benefit of 2.5 years compared with the untreated patients with HGPS. This large treatment effect on the objective endpoint of mortality using a well-matched comparator group mitigated potential sources of bias and together with other evidence, established compelling evidence of a drug effect with benefits that outweighed the risks. This approval is an example of U.S. Food and Drug Administration's regulatory flexibility for a rare disease while ensuring that standards for drug approval are met.

Loss-of-function mutations in ISCA2 disrupt 4Fe-4S cluster machinery and cause a fatal leukodystrophy with hyperglycinemia and mtDNA depletion.

Iron-sulfur (Fe-S) clusters are essential cofactors for proteins that participate in fundamental cellular processes including metabolism, DNA replication and repair, transcriptional regulation, and the mitochondrial electron transport chain (ETC). ISCA2 plays a role in the biogenesis of Fe-S clusters and a recent report described subjects displaying infantile-onset leukodystrophy due to bi-allelic mutation of ISCA2. We present two additional unrelated cases, and provide a more complete clinical description that includes hyperglycinemia, leukodystrophy of the brainstem with longitudinally extensive spinal cord involvement, and mtDNA deficiency. Additionally, we characterize the role of ISCA2 in mitochondrial bioenergetics and Fe-S cluster assembly using subject cells and ISCA2 cellular knockdown models. Loss of ISCA2 diminished mitochondrial membrane potential, the mitochondrial network, basal and maximal respiration, ATP production, and activity of ETC complexes II and IV. We specifically tested the impact of loss of ISCA2 on 2Fe-2S proteins versus 4Fe-4S proteins and observed deficits in the functioning of 4Fe-4S but not 2Fe-2S proteins. Together these data indicate loss of ISCA2 impaired function of 4Fe-4S proteins resulting in a fatal encephalopathy accompanied by a relatively unusual combination of features including mtDNA depletion alongside complex II deficiency and hyperglycinemia that may facilitate diagnosis of ISCA2 deficiency patients.

Noonan syndrome in diverse populations.

Noonan syndrome (NS) is a common genetic syndrome associated with gain of function variants in genes in the Ras/MAPK pathway. The phenotype of NS has been well characterized in populations of European descent with less attention given to other groups. In this study, individuals from diverse populations with NS were evaluated clinically and by facial analysis technology. Clinical data and images from 125 individuals with NS were obtained from 20 countries with an average age of 8 years and female composition of 46%. Individuals were grouped into categories of African descent (African), Asian, Latin American, and additional/other. Across these different population groups, NS was phenotypically similar with only 2 of 21 clinical elements showing a statistically significant difference. The most common clinical characteristics found in all population groups included widely spaced eyes and low-set ears in 80% or greater of participants, short stature in more than 70%, and pulmonary stenosis in roughly half of study individuals. Using facial analysis technology, we compared 161 Caucasian, African, Asian, and Latin American individuals with NS with 161 gender and age matched controls and found that sensitivity was equal to or greater than 94% for all groups, and specificity was equal to or greater than 90%. In summary, we present consistent clinical findings from global populations with NS and additionally demonstrate how facial analysis technology can support clinicians in making accurate NS diagnoses. This work will assist in earlier detection and in increasing recognition of NS throughout the world.

Childhood Rhabdomyosarcoma in Association With a RASopathy Clinical Phenotype and Mosaic Germline SOS1 Duplication.

Childhood rhabdomyosarcoma (RMS) accounts for approximately 3.5% of cancer cases among children 0 to 14 years of age. Genetic conditions associated with high risk of childhood RMS include Li-Fraumeni syndrome, pleuropulmonary blastoma, Beckwith-Wiedemann syndrome, and some RASopathies, such as neurofibromatosis type 1, Costello syndrome (CS), and Noonan syndrome (NS). Here, we report the rare case of a 4-year-old girl with clinical features of NS who developed an embryonal RMS of the chest and needed emergent treatment. Molecular genetic testing identified a de novo, large, mosaic duplication of chromosome 2 encompassing the SOS1 gene, presumably caused by a mosaic, unbalanced translocation between chromosomes 2 and 17 found on routine cytogenetic analysis. Sequence analysis of all known genes causing Noonan spectrum disorders was negative. RMS has been reported in a few patients with NS, associated in very few with germline SOS1 mutations, but none with copy number abnormalities. This is the first report to our knowledge of early-onset RMS developing in a child with features of NS and a mosaic RAS pathway gene aberration, a large SOS1 duplication. We hypothesize that the inciting event for tumor development in this case is due to the germline mosaic duplication of SOS1, which was duplicated in all cells of the tumor, and the ultimate development of the tumor was further driven by multiple chromosomal aberrations in the tumor itself, all described as somatic events in isolated RMS tumors.

Menkes disease in affected females: the clinical disease spectrum.

Menkes disease (MD; OMIM 309400) is an X-linked, neurodegenerative disorder resulting from deficient activity of copper-dependent enzymes and caused by alterations in the APT7A gene. In its classic form, it manifests in boys with hypotonia, seizures, skin and joint laxity, hair twisting (pili torti), cerebrovascular tortuosity, and bladder diverticulae. Menkes disease phenotypes have been reported in females with X; autosome translocations-disrupting ATP7A gene function- or ATP7A gene alterations. Those females manifest variable clinical findings, some of which, such as pili torti, seizure presence and/or age of onset, cerebrovascular tortuosity, degree of intellectual disability, and bladder divericulae are largely under-reported and under-studied. Here, we report on three females with Menkes disease and variant phenotypes, sharing characteristic features, one with classic Menkes disease and two with Menkes disease variants. We conclude that Menkes disease in females manifests with a variable spectrum of clinical findings but a few are uniformly present such as neurodevelopmental disability, hypotonia, and connective tissue findings. Others, such as seizures, cerebral atrophy, and cerebrovascular tortuosity may be present but are under-reported and under- studied. We propose that the diagnosis of Menkes disease or variants in females with suspicious clinical findings is an important one to consider as early treatment with parenteral copper may be considered. The effect of this treatment on the disease course in females with MD is unknown and remains to be seen.

An attenuated phenotype of Costello syndrome in three unrelated individuals with a HRAS c.179G>A (p.Gly60Asp) mutation correlates with uncommon functional consequences.

Heterozygous germline mutations in the proto-oncogene HRAS cause Costello syndrome (CS), an intellectual disability condition with severe failure to thrive, cardiac abnormalities, predisposition to tumors, and neurologic abnormalities. More than 80% of patients share the HRAS mutation c.34G>A (p.Gly12Ser) associated with the typical, relatively homogeneous phenotype. Rarer mutations occurred in individuals with an attenuated phenotype and less characteristic facial features. Most pathogenic HRAS alterations affect hydrolytic HRAS activity resulting in constitutive activation. "Gain-of-function" and "hyperactivation" concerning downstream pathways are widely used to explain the molecular basis and dysregulation of the RAS-MAPK pathway is the biologic mechanism shared amongst rasopathies. Panel testing for rasopathies identified a novel HRAS mutation (c.179G>A; p.Gly60Asp) in three individuals with attenuated features of Costello syndrome. De novo paternal origin occurred in two, transmission from a heterozygous mother in the third. Individuals showed subtle facial features; curly hair and relative macrocephaly were seen in three; atrial tachycardia and learning difficulties in two, and pulmonic valve dysplasia and mildly thickened left ventricle in one. None had severe failure to thrive, intellectual disability or cancer, underscoring the need to consider HRAS mutations in individuals with an unspecific rasopathy phenotype. Functional studies revealed strongly increased HRAS(Gly60Asp) binding to RAF1, but not to other signaling effectors. Hyperactivation of the MAPK downstream signaling pathways was absent. Our results indicate that an increase in the proportion of activated RAS downstream signaling components does not entirely explain the molecular basis of CS. We conclude that the phenotypic variability in CS recapitulates variable qualities of molecular dysfunction.

Important Considerations in the Initial Clinical Evaluation of the Dysmorphic Neonate.

BACKGROUND: The approach to clinical evaluation of the dysmorphic neonate can be challenging and multifaceted. It requires specialized knowledge of rare diagnoses and awareness of immediate versus long-term needs for the newborn and the family. PURPOSE: This review summarizes important considerations in the initial evaluation of genetic syndromes, which can present in the neonatal period with variable aspects of dysmorphism. METHODS: An overview of the literature in this area is provided. FINDINGS/RESULTS: Several overlapping areas of concern for working with this population are addressed, including communication with the family, fundamentals of the physical examination, common genetic disorders, syndromes, as well as palliative care and end of life decision making for the newborn in the context of family needs. IMPLICATIONS FOR PRACTICE: The initial approach for the neonatal practitioner needs to focus on various aspects of the newborn's care, including medical stabilization, determining whether immediate laboratory or imaging studies are needed, careful physical examination with particular attention to detail, appropriate and timely communication with the family, and knowledge of various specific aspects of rare diseases. IMPLICATIONS FOR RESEARCH: More research is needed to better understand how to best support the newborn born with dysmorphia or a rare disease. Particular attention needs to be focused on strategies to best support the family who is often in crisis during the neonatal period.

Dose selection for biological enzyme replacement therapy indicated for inborn errors of metabolism.

This paper summarizes key features of the dose-finding strategies used in the development of 11 approved new molecular entities that are first-in-class enzyme replacement therapy (ERT), with a goal to gain insight into the dose exploration approaches to inform efficient dose-finding in future development of biological products for Inborn Errors of Metabolism (IEM). Dose exploration should preferably begin in in vitro studies, followed by testing multiple doses in an appropriate animal disease model, when available, which can provide important information for dose assessment in humans. Performing adequate dose-finding in early phase clinical studies in a well-defined study population, including pediatric subjects, is generally critical to inform dose selection for pivotal trials; alternatively, additional dose exploration can be incorporated as part of a pivotal trial. Two important considerations for successful dose selection include (1) identifying appropriate disease-specific endpoints, including pharmacodynamic (PD) end points and intermediate clinical end points or clinical end points, and (2) designing a study with adequate treatment durations for evaluating these end points. Appropriately selected PD biomarkers is useful for dose selection, and early development of these biomarkers can facilitate the overall clinical development program. Optimization of ERT doses, as well as evaluations of patient intrinsic factors and/or immune tolerance strategies may be necessary to overcome antibody responses or increase efficacy in IEM.

Medical complications, clinical findings, and educational outcomes in adults with Noonan syndrome.

Noonan syndrome (NS) is a heterogeneous developmental disorder caused by missense mutations in genes involved in the Ras/MAPK signaling pathway, a major mediator of early and late developmental processes. The diagnosis of NS is made on clinical grounds with molecular confirmation of a mutation found in 63% of cases. Key clinical features include short stature, cardiac defects, developmental delay, lymphatic dysplasias, bleeding tendency, and a constellation of distinctive facial features and physical exam findings. The prevalence of medical issues or the development of new ones in adults with NS is not well-studied. This cross-sectional study reports on the prevalence of clinical conditions and their ages of onset in a cohort of 35 adolescents and adults with NS aged 16-68 years old (mean age 28 years). In this cohort, 34 of 35 subjects (97%) had had full PTPN11 sequencing; 37% were PTPN11 positive, 23% were SOS1 positive, and 3% were BRAF positive. Mean adult height in both men and women was at the 3rd-10th centile. The most prevalent clinical findings in this cohort included pulmonary valve stenosis (71%), easy bruising (63%), GERD (60%), constipation (51%), scoliosis (54%), chronic joint pain (54%), lymphedema (49%), depression (49%), anxiety (49%), Chiari malformation (20%), and osteopenia/osteoporosis (14%). In summary, adults with NS are affected by multi-organ morbidity and require special medical management aimed towards the most prevalent and serious known medical complications. Larger studies characterizing the clinical conditions found in NS adults are needed to provide potential genotype-phenotype correlations that may aid in clinical management.

Expanding Approved Patient Populations for Rare Disease Treatment Using In Vitro Data.

In vitro cell-based data can be used to support the extension of pharmaceutical approval to patient subsets with unique genetic variants. A set of conditions should be satisfied to support the extension of approval. The disease mechanism should be well described, and the impact of variants on protein function should be reasonably understood. The incidence data should show that clinical trials for the variants in question are not practical. The overall safety and efficacy of the drug should be clear in adequate and well-controlled clinical trials. The clinical trial should include patients found to be responders and nonresponders so that both positive and negative predictive power of the in vitro assay may be measured. The mechanism of action of the drug should be clearly defined and should be consistent with the disease mechanism. The assay system should be qualified, including the following points: (i) each variant construct should be confirmed by bidirectional sequencing; (ii) the in vitro assay should directly measure the variant protein function in comparison with the reference protein; (iii) the assay should be formally validated to the extent possible, clearly demonstrating precision, reproducibility, and sensitivity used to support the efficacy claim; and (iv) the primary data should be available for inspection and analytical validation. The overall goal is a robust and validated cell-based system that can be shown to predict the outcome of targeted therapy.

PTEN hamartoma tumour syndrome: early tumour development in children.

OBJECTIVE: The aim of this study was to report the earliest age of diagnosis of common clinical findings in children with PTEN hamartoma tumour syndrome (PHTS). DESIGN: Medical records of children with PHTS were reviewed; data included growth measurements, presence or absence of specific clinical manifestations and tumours, and documented ages of diagnosis. SETTING: Children with PHTS evaluated at Boston Children's Hospital from 1996 to 2011. PATIENTS: The cohort included 34 children diagnosed with PHTS via genetic testing, under the age of 21 years. Of these, 23 were male and 11 female. The mean age at their last documented clinical evaluation was 13.6 years. The mean follow-up time was 7.5 years. RESULTS: Macrocephaly and developmental/intellectual disability were consistent findings. Pigmented penile macules were noted in all males examined for this finding. Thyroid nodules, found in half the children screened with ultrasound, were diagnosed as early as at 5 years of age. Thyroid carcinoma, identified in 12% of the children in this cohort, was diagnosed as early as at 7 years of age. Other tumours included renal cell carcinoma diagnosed at 11 years of age and granulosa cell tumour of the ovary and colonic ganglioneuroma, each diagnosed at 16 years of age. CONCLUSIONS: Specific clinical findings and tumours are characteristic in children with PHTS. Tumour development occurs in young children with this condition, which necessitates early surveillance, especially of the thyroid.

Thiamine pyrophosphokinase deficiency causes a Leigh Disease like phenotype in a sibling pair: identification through whole exome sequencing and management strategies.

We present a sibling pair with Leigh-like disease, progressive hypotonia, regression, and chronic encephalopathy. Whole exome sequencing in the younger sibling demonstrated a homozygous thiamine pyrophosphokinase (TPK) mutation. Initiation of high dose thiamine, niacin, biotin, α-lipoic acid and ketogenic diet in this child demonstrated improvement in neurologic function and re-attainment of previously lost milestones. The diagnosis of TPK deficiency was difficult due to inconsistent biochemical and diagnostic parameters, rapidity of clinical demise and would not have been made in a timely manner without the use of whole exome sequencing. Molecular diagnosis allowed for attempt at dietary modification with cofactor supplementation which resulted in an improved clinical course.