Loren D.M. Pena

Clinical delineation and natural history of the PIK3CA -related overgrowth spectrum

Somatic mutations in the phosphatidylinositol/AKT/mTOR pathway cause segmental overgrowth disorders. Diagnostic descriptors associated with PIK3CA mutations include fibroadipose overgrowth (FAO), Hemihyperplasia multiple Lipomatosis (HHML), Congenital Lipomatous Overgrowth, Vascular malformations, Epidermal nevi, Scoliosis/skeletal and spinal (CLOVES) syndrome, macrodactyly, and the megalencephaly syndrome, Megalencephaly‐Capillary malformation (MCAP) syndrome. We set out to refine the understanding of the clinical spectrum and natural history of these phenotypes, and now describe 35 patients with segmental overgrowth and somatic PIK3CA mutations. The phenotypic data show that these previously described disease entities have considerable overlap, and represent a spectrum. While this spectrum overlaps with Proteus syndrome (sporadic, mosaic, and progressive) it can be distinguished by the absence of cerebriform connective tissue nevi and a distinct natural history. Vascular malformations were found in 15/35 (43%) and epidermal nevi in 4/35 (11%) patients, lower than in Proteus syndrome. Unlike Proteus syndrome, 31/35 (89%) patients with PIK3CA mutations had congenital overgrowth, and in 35/35 patients this was asymmetric and disproportionate. Overgrowth was mild with little postnatal progression in most, while in others it was severe and progressive requiring multiple surgeries. Novel findings include: adipose dysregulation present in all patients, unilateral overgrowth that is predominantly left‐sided, overgrowth that affects the lower extremities more than the upper extremities and progresses in a distal to proximal pattern, and in the most severely affected patients is associated with marked paucity of adipose tissue in unaffected areas. While the current data are consistent with some genotype–phenotype correlation, this cannot yet be confirmed.

Natural history of propionic acidemia.

Propionic acidemia is an organic acidemia that can lead to metabolic acidosis, coma and death, if not treated appropriately in the acute setting. Recent advancements in treatment have allowed patients with propionic acidemia to live beyond the neonatal period and acute presentation. The natural history of the disease is just beginning to be elucidated as individuals reach older ages. Recent studies have identified the genomic mutations in the genes PCCA and PCCB. However, as of yet no clear genotype-phenotype correlations are known. As patients age, the natural progression of propionic acidemia illuminates intellectual difficulties, increased risk for neurological complications, including stroke-like episodes, cardiac complications, and gastrointestinal difficulties, as well as a number of other complications. This article reviews the available literature for the natural history of propionic acidemia.

Acute management of propionic acidemia.

Propionic acidemia or aciduria is an intoxication-type disorder of organic metabolism. Patients deteriorate in times of increased metabolic demand and subsequent catabolism. Metabolic decompensation can manifest with lethargy, vomiting, coma and death if not appropriately treated. On January 28-30, 2011 in Washington, D.C., Childrens National Medical Center hosted a group of clinicians, scientists and parental group representatives to design recommendations for acute management of individuals with propionic acidemia. Although many of the recommendations are geared toward the previously undiagnosed neonate, the recommendations for a severely metabolically decompensated individual are applicable to any known patient as well. Initial management is critical for prevention of morbidity and mortality. The following manuscript provides recommendations for initial treatment and evaluation, a discussion of issues concerning transport to a metabolic center (if patient presents to a non-metabolic center), acceleration of management and preparation for discharge.

Chronic management and health supervision of individuals with propionic acidemia

Propionic acidemia is a relatively rare inborn error of metabolism. Individuals with propionic acidemia often have life-threatening episodes of hyperammonemia and metabolic acidosis, as well as intellectual disability. There are many reports of additional problems, including poor growth, stroke-like episodes of the basal ganglia, seizures, cardiomyopathy, long QTc syndrome, immune defects, pancreatitis and optic neuropathy; however, there is little information about the incidence of these problems in this rare disease. Additionally, there are no clear guidelines for medical or surgical management of individuals with propionic acidemia. Through a comprehensive and systematic review of the current medical literature and survey of expert opinion, we have developed practice guidelines for the chronic management of individuals with propionic acidemia, including dietary therapy, use of medications, laboratory monitoring, chronic health supervision, use of gastrostomy tubes and liver transplantation.

Neurologic considerations in propionic acidemia.

Propionic acidemia (PA) is an organic acidemia which has a broad range of neurological complications, including developmental delay, intellectual disability, structural abnormalities, metabolic stroke-like episodes, seizures, optic neuropathy, and cranial nerve abnormalities. As the PA consensus conference hosted by Childrens National Medical Center progressed from January 28 to 30, 2011, it became evident that neurological complications were common and a major component of morbidity, but the role of imaging and the basis for brain pathophysiology were unclear. This paper reviews the hypothesized pathophysiology, presentation and uses the best available evidence to suggest programs for treatment, imaging, and monitoring the neurological complications of PA.

Survey of health status and complications among propionic acidemia patients

Propionic acidemia (PA) is a rare organic acidemia that is due to deficiency in the enzyme propionyl‐coA carboxylase. Complications are currently described mostly in the form of case reports. We sampled a population of affected individuals in order to estimate the frequency of complications amongst the sample. The study is a cross‐sectional retrospective review with a survey instrument and recruitment through the Propionic Acidemia Foundation. Responses for 58 individuals were tabulated for each question as how frequently the complication was reported among responders. Commonly reported findings included seizures, arrhythmia, leucopenia, and anemia. Developmental and cognitive disabilities were reported in the majority of individuals. Heart failure or cardiomyopathy was reported in over half of deceased individuals at time of death. Pancreatitis was reported in a minority of the sample, yet more than half of these reported a recurrence. These results update and extend our current knowledge of recognized complications among individuals with PA. The results also provide new information regarding developmental outcomes and previously unreported morbidity from cardiac and gastrointestinal complications. Longitudinal studies exploring associated biochemical and clinical parameters are necessary to further our understanding of the pathophysiology of PA and its complications.

Not the End of the Odyssey: Parental Perceptions of Whole Exome Sequencing (WES) in Pediatric Undiagnosed Disorders

Due to the lack of empirical information on parental perceptions of primary results of whole exome sequencing (WES), we conducted a retrospective semi-structured interview with 19 parents of children who had undergone WES. Perceptions explored during the interview included factors that would contribute to parental empowerment such as: parental expectations, understanding of the WES and results, utilization of the WES information, and communication of findings to health/educational professionals and family members. Results of the WES had previously been communicated to families within a novel framework of clinical diagnostic categories: 5/19 had Definite diagnoses, 6/19 had Likely diagnoses, 3/19 had Possible diagnosis and 5/19 had No diagnosis. All parents interviewed expressed a sense of duty to pursue the WES in search of a diagnosis; however, their expectations were tempered by previous experiences with negative genetic testing results. Approximately half the parents worried that a primary diagnosis that would be lethal might be identified; however, the hope of a diagnosis outweighed this concern. Parents were accurately able to summarize their child’s WES findings, understood the implications for recurrence risks, and were able to communicate these findings to family and medical/educational providers. The majority of those with a Definite/Likely diagnosis felt that their child’s medical care was more focused, or there was a reduction in worry, despite the lack of a specific treatment. Irrespective of diagnostic outcome, parents recommended that follow-up visits be built into the process. Several parents expressed a desire to have all variants of unknown significance (VUS) reported to them so that they could investigate these themselves. Finally, for some families whose children had a Definite/Likely diagnosis, there was remaining frustration and a sense of isolation, due to the limited information that was available about the diagnosed rare disorders and the inability to connect to other families, suggesting that for families with rare genetic disorders, the diagnostic odyssey does not necessarily end with a diagnosis. Qualitative interviewing served a meaningful role in eliciting new information about parental motivations, expectations, and knowledge of WES. Our findings highlight a need for continued communication with families as we navigate the new landscape of genomic sequencing.

Outcomes and genotype-phenotype correlations in 52 individuals with VLCAD deficiency diagnosed by NBS and enrolled in the IBEM-IS database

Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency can present at various ages from the neonatal period to adulthood, and poses the greatest risk of complications during intercurrent illness or after prolonged fasting. Early diagnosis, treatment, and surveillance can reduce mortality; hence, the disorder is included in the newborn Recommended Uniform Screening Panel (RUSP) in the United States. The Inborn Errors of Metabolism Information System (IBEM-IS) was established in 2007 to collect longitudinal information on individuals with inborn errors of metabolism included in newborn screening (NBS) programs, including VLCAD deficiency. We retrospectively analyzed early outcomes for individuals who were diagnosed with VLCAD deficiency by NBS and describe initial presentations, diagnosis, clinical outcomes and treatment in a cohort of 52 individuals ages 1-18years. Maternal prenatal symptoms were not reported, and most newborns remained asymptomatic. Cardiomyopathy was uncommon in the cohort, diagnosed in 2/52 cases. Elevations in creatine kinase were a common finding, and usually first occurred during the toddler period (1-3years of age). Diagnostic evaluations required several testing modalities, most commonly plasma acylcarnitine profiles and molecular testing. Functional testing, including fibroblast acylcarnitine profiling and white blood cell or fibroblast enzyme assay, is a useful diagnostic adjunct if uncharacterized mutations are identified.

Prospective exploratory muscle biopsy, imaging, and functional assessment in patients with late-onset Pompe disease treated with alglucosidase alfa: The EMBASSY Study

BACKGROUND Late-onset Pompe disease is characterized by progressive skeletal myopathy followed by respiratory muscle weakness, typically leading to loss of ambulation and respiratory failure. In this population, enzyme replacement therapy (ERT) with alglucosidase alfa has been shown to stabilize respiratory function and improve mobility and muscle strength. Muscle pathology and glycogen clearance from skeletal muscle in treatment-naïve adults after ERT have not been extensively examined. METHODS This exploratory, open-label, multicenter study evaluated glycogen clearance in muscle tissue samples collected pre- and post- alglucosidase alfa treatment in treatment-naïve adults with late-onset Pompe disease. The primary endpoint was the quantitative reduction in percent tissue area occupied by glycogen in muscle biopsies from baseline to 6months. Secondary endpoints included qualitative histologic assessment of tissue glycogen distribution, secondary pathology changes, assessment of magnetic resonance images (MRIs) for intact muscle and fatty replacement, and functional assessments. RESULTS Sixteen patients completed the study. After 6months of ERT, the percent tissue area occupied by glycogen in quadriceps and deltoid muscles decreased in 10 and 8 patients, respectively. No changes were detected on MRI from baseline to 6months. A majority of patients showed improvements on functional assessments after 6months of treatment. All treatment-related adverse events were mild or moderate. CONCLUSIONS This exploratory study provides novel insights into the histopathologic effects of ERT in late-onset Pompe disease patients. Ultrastructural examination of muscle biopsies demonstrated reduced lysosomal glycogen after ERT. Findings are consistent with stabilization of disease by ERT in treatment-naïve patients with late-onset Pompe disease.

A window into living with an undiagnosed disease: illness narratives from the Undiagnosed Diseases Network

AbstractBackgroundPatients’ stories of their illnesses help bridge the divide between patients and providers, facilitating more humane medical care. Illness narratives have been classified into three types: restitution (expectation of recovery), chaos (suffering and loss), and quest (unexpected positive effect from illness). Undiagnosed patients have unique illness experiences and obtaining their narratives would provide insights into the medical and emotional impact of living with an undiagnosed illness. Adults and children with undiagnosed diseases apply to be evaluated by the Undiagnosed Diseases Network (UDN). Written illness narratives from 40 UDN applicants, including 20 adult probands who applied for themselves and 20 parents who applied for their children, were analyzed for: 1) narrative content and 2) narrative type.ResultsNarrative content: could be grouped into three themes: 1) Expectations of the UDN: the majority felt they had no further healthcare options and hoped the UDN would provide them with a diagnosis, with the adults expecting to return to their previously healthy life and the parents wanting information to manage their child’s healthcare. 2) Personal medical information: the narratives reported worsening of symptoms and some offered opinions regarding the cause of their illness. The proband narratives had few objective findings, while parental narratives had detailed objective information. 3) Experiences related to living with their undiagnosed illness: frustration at being undiagnosed was expressed. The adults felt they had to provide validation of their symptoms to providers, given the lack of objective findings. The parents worried that something relevant to their child’s management was being overlooked. Narrative type: All the narratives were of the chaos type, but for different reasons, with the probands describing loss and suffering and the parents expressing fear for their child’s future. The parental narratives also had elements of restitution and quest, with acceptance of “a new normal”, and an emphasis on the positive aspects of their child’s illness which was absent from the probands.ConclusionsThese narratives illustrate the chaos that coexists with being undiagnosed. The differences between the proband and parental narratives suggest that these two groups have different needs that need to be considered during their evaluation and management.