Spectrum of KV 2.1 Dysfunction in KCNB1-Associated Neurodevelopmental Disorders.

OBJECTIVE: Pathogenic variants in KCNB1, encoding the voltage-gated potassium channel KV 2.1, are associated with developmental and epileptic encephalopathy (DEE). Previous functional studies on a limited number of KCNB1 variants indicated a range of molecular mechanisms by which variants affect channel function, including loss of voltage sensitivity, loss of ion selectivity, and reduced cell-surface expression. METHODS: We evaluated a series of 17 KCNB1 variants associated with DEE or other neurodevelopmental disorders (NDDs) to rapidly ascertain channel dysfunction using high-throughput functional assays. Specifically, we investigated the biophysical properties and cell-surface expression of variant KV 2.1 channels expressed in heterologous cells using high-throughput automated electrophysiology and immunocytochemistry-flow cytometry. RESULTS: Pathogenic variants exhibited diverse functional defects, including altered current density and shifts in the voltage dependence of activation and/or inactivation, as homotetramers or when coexpressed with wild-type KV 2.1. Quantification of protein expression also identified variants with reduced total KV 2.1 expression or deficient cell-surface expression. INTERPRETATION: Our study establishes a platform for rapid screening of KV 2.1 functional defects caused by KCNB1 variants associated with DEE and other NDDs. This will aid in establishing KCNB1 variant pathogenicity and the mechanism of dysfunction, which will enable targeted strategies for therapeutic intervention based on molecular phenotype. ANN NEUROL 2019;86:899-912.

Focal Cerebral Arteriopathy of Childhood: Novel Severity Score and Natural History.

Background and Purpose- Focal cerebral arteriopathy (FCA)-a common cause of arterial ischemic stroke in previously healthy children-often progresses over days to weeks, increasing the risk of recurrent stroke. We developed a novel severity scoring system designed to quantify FCA progression and correlate with clinical outcomes. Methods- The VIPS study (Vascular Effects of Infection in Pediatric Stroke) prospectively enrolled 355 children with arterial ischemic stroke (2010-2014), including 41 with centrally confirmed FCA. Two neuroradiologists independently reviewed FCA cerebrovascular imaging, assigning a graded severity score of zero (no involvement) to 4 (occlusion) to individual arterial segments. The FCA severity score (FCASS) was the unweighted sum. In an iterative process, we modeled scores derived from different combinations of arterial segments to identify the model that optimized correlation with clinical outcome, simplicity, and reliability. Results- The optimal FCASS summed scores from 5 arterial segments: supraclinoid internal carotid artery, A1, A2, M1, and M2. The median (interquartile range) baseline FCASS was 4 (2-6). Of 33 children with follow-up imaging, the maximum FCASS (at any time point) was 7 (5-9). Twenty-four (73%) had FCA progression on follow-up with their maximum FCASS at a median of 8 (5-35.5) days poststroke; their median FCASS increase was 4 (2.5-6). FCASS did not correlate with recurrent arterial ischemic stroke. Maximum (but not baseline) FCASS correlated with 1-year pediatric stroke outcome measures ( P=0.037). Conclusions- Our novel scoring system for FCA severity correlates with neurological outcomes in the VIPS cohort and provides a tool for FCA treatment trials under development.

Arteriopathy diagnosis in childhood arterial ischemic stroke: results of the vascular effects of infection in pediatric stroke study.

BACKGROUND AND PURPOSE: Although arteriopathies are the most common cause of childhood arterial ischemic stroke, and the strongest predictor of recurrent stroke, they are difficult to diagnose. We studied the role of clinical data and follow-up imaging in diagnosing cerebral and cervical arteriopathy in children with arterial ischemic stroke. METHODS: Vascular effects of infection in pediatric stroke, an international prospective study, enrolled 355 cases of arterial ischemic stroke (age, 29 days to 18 years) at 39 centers. A neuroradiologist and stroke neurologist independently reviewed vascular imaging of the brain (mandatory for inclusion) and neck to establish a diagnosis of arteriopathy (definite, possible, or absent) in 3 steps: (1) baseline imaging alone; (2) plus clinical data; (3) plus follow-up imaging. A 4-person committee, including a second neuroradiologist and stroke neurologist, adjudicated disagreements. Using the final diagnosis as the gold standard, we calculated the sensitivity and specificity of each step. RESULTS: Cases were aged median 7.6 years (interquartile range, 2.8-14 years); 56% boys. The majority (52%) was previously healthy; 41% had follow-up vascular imaging. Only 56 (16%) required adjudication. The gold standard diagnosis was definite arteriopathy in 127 (36%), possible in 34 (9.6%), and absent in 194 (55%). Sensitivity was 79% at step 1, 90% at step 2, and 94% at step 3; specificity was high throughout (99%, 100%, and 100%), as was agreement between reviewers (κ=0.77, 0.81, and 0.78). CONCLUSIONS: Clinical data and follow-up imaging help, yet uncertainty in the diagnosis of childhood arteriopathy remains. This presents a challenge to better understanding the mechanisms underlying these arteriopathies and designing strategies for prevention of childhood arterial ischemic stroke.

Emergence of the primary pediatric stroke center: impact of the thrombolysis in pediatric stroke trial.

BACKGROUND AND PURPOSE: In adult stroke, the advent of thrombolytic therapy led to the development of primary stroke centers capable to diagnose and treat patients with acute stroke rapidly. We describe the development of primary pediatric stroke centers through preparation of participating centers in the Thrombolysis in Pediatric Stroke (TIPS) trial. METHODS: We collected data from the 17 enrolling TIPS centers regarding the process of becoming an acute pediatric stroke center with capability to diagnose, evaluate, and treat pediatric stroke rapidly, including use of thrombolytic therapy. RESULTS: Before 2004, <25% of TIPS sites had continuous 24-hour availability of acute stroke teams, MRI capability, or stroke order sets, despite significant pediatric stroke expertise. After TIPS preparation, >80% of sites now have these systems in place, and all sites reported increased readiness to treat a child with acute stroke. Use of a 1- to 10-Likert scale on which 10 represented complete readiness, median center readiness increased from 6.2 before site preparation to 8.7 at the time of site activation (P≤0.001). CONCLUSIONS: Before preparing for TIPS, centers interested in pediatric stroke had not developed systematic strategies to diagnose and treat acute pediatric stroke. TIPS trial preparation has resulted in establishment of pediatric acute stroke centers with clinical and system preparedness for evaluation and care of children with acute stroke, including use of a standardized protocol for evaluation and treatment of acute arterial stroke in children that includes use of intravenous tissue-type plasminogen activator. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT01591096.

Evidence of varicella zoster virus (VZV) reactivation in children with arterial ischemic stroke: Results of the VIPS II Study.

Background: Varicella zoster virus (VZV) has been associated with focal cerebral arteriopathy (FCA) and arterial ischemic stroke (AIS) in childhood. The Vascular effects of Infection in Pediatric Stroke (VIPS) II study aimed to examine this relationship in the modern era when most children in North America and Australia receive VZV vaccination with live, attenuated virus. Methods: This 22-center prospective cohort study enrolled 205 children (28 days-18 years) with AIS (2017-2022), collected baseline [hyperacute (≤72 hours; n=194) and acute (4-6 days; n=181)] and convalescent (1-6 weeks; n=74) serum samples. Sites enrolled 95 stroke-free controls with single serum samples. A virology research laboratory measured VZV IgM and IgG titers by an in-house enzyme-linked immunosorbent assay (ELISA). Baseline IgG seropositivity indicated prior exposure (vaccination/infection) and elevated IgM titers indicated recent reactivation. Results: Median (IQR) age was 11.6 (5.5-15.6) years for cases and 11.8 (6.8-15.3) years for controls. Baseline serologies indicated prior VZV exposure in 198 cases (97%) and all controls. Parents of cases reported VZV vaccination in 160 (78%) and remote chicken pox in three (1.4%). Twenty cases (9.8%) and three controls (3.1%) had serologic evidence of recent VZV reactivation (p=0.06); all had remote VZV exposure (vaccination in 19 cases and all controls) and all were asymptomatic. Recent VZV reactivation was seen in similar proportions in arteriopathic, cardioembolic, and idiopathic stroke. Of 32 cases of FCA, 4 (12.5%) had recent VZV reactivation, versus no cases of arterial dissection (n=10) or moyamoya (n=16). Conclusions: Serologic evidence of recent VZV reactivation (≈1-6 weeks prior to stroke) was present in one in 10 cases of childhood AIS, including those without arteriopathy. Clinically silent VZV reactivation may be a childhood stroke trigger despite widespread vaccination. These cases could represent waning immunity with reactivation of either vaccine virus or wild-type virus after an unrecognized secondary VZV infection.

Exploring the neurological features of individuals with germline PTEN variants: A multicenter study.

OBJECTIVE: PTEN, a known tumor suppressor gene, is a mediator of neurodevelopment. Individuals with germline pathogenic variants in the PTEN gene, molecularly defined as PTEN hamartoma tumor syndrome (PHTS), experience a variety of neurological and neuropsychiatric challenges during childhood, including autism spectrum disorder (ASD). However, the frequency and nature of seizures and the utilization of allied health services have not been described. METHODS: Young patients with PHTS and sibling controls were recruited across five centers in the United States and followed every 6-12 months for a mean of 2.1 years. In addition to the history obtained from caregivers, neurodevelopmental evaluations and structured dysmorphology examinations were conducted, and brain MRI findings, received therapies, and epilepsy characteristics were reported. RESULTS: One hundred and seven patients with PHTS (median age 8.7 years; range 3-21 years) and 38 controls were enrolled. ASD and epilepsy were frequent among patients with PHTS (51% and 15%, respectively), with generalized epilepsy strongly associated with ASD. Patients with epilepsy often required two antiseizure medications. Neuroimaging revealed prominent perivascular spaces and decreased peritrigonal myelination in individuals with PHTS-ASD. Allied therapy use was frequent and involved physical, occupational, speech, and social skills therapies, with 89% of all patients with PHTS, regardless of ASD diagnosis, utilizing at least one service. INTERPRETATION: This prospective, longitudinal study highlights the wide neurological spectrum seen in young individuals with PHTS. ASD is common in PHTS, comorbid with epilepsy, and allied health services are used universally. Our findings inform care discussions with families about neurological outcomes in PHTS.

Phosphoribosylpyrophosphate synthetase superactivity and recurrent infections is caused by a p.Val142Leu mutation in PRS-I.

We identified a novel missense mutation, c.424G>C (p.Val142Leu) in PRPS1 in a patient with uric acid overproduction without gout but with developmental delay, hypotonia, hearing loss, and recurrent respiratory infections. The uric acid overproduction accompanying this combination of symptoms suggests that the patient presented with phosphoribosylpyrophosphate (PRPP) synthetase superactivity, but recurrent infections have not been associated with superactivity until now. However, recurrent infections are a prominent feature of patients with Arts syndrome, which is caused by PRPS1 loss-of-function mutations, indicating that the patient reported here has an intermediate phenotype. Molecular modeling predicts that the p.Val142Leu change affects both allosteric sites that are involved in inhibition of PRPS1 and the ATP-binding site, which suggests that this substitution can result both in a gain-of-function and loss-of-function of PRPP synthetase. This finding is in line with the normal PRPP synthetase activity in fibroblasts and the absence of activity in erythrocytes of the present patient. We postulate that the overall effect of the p.Val142Leu change on protein activity is determined by the cell type, being a gain-of-function in proliferating cells and a loss-of-function in postmitotic cells. Our results show that missense mutations in PRPS1 can cause a continuous spectrum of features ranging from progressive non-syndromic postlingual hearing impairment to uric acid overproduction, neuropathy, and recurrent infections depending on the functional sites that are affected.

Scoring of brain magnetic resonance imaging and neurodevelopmental outcomes in infants with congenital heart disease.

BACKGROUND: Advances in surgical techniques to tackle critical congenital heart diseases (CHD) have enhanced the survival rates and life expectancy of children born with heart disease. Studies to better acknowledge their neurodevelopmental trajectory have paramount implications. OBJECTIVE: The aim of this study is to examine the nature of brain MRI findings in infants born with critical congenital heart diseases needing intervention in the first 6 months of life, with the help of an MRI scoring system and correlation with long term neurodevelopmental outcomes. METHODS: Brain MRI scans of eligible infants were extracted from database, reexamined to categorize, and score them into three main functional areas: cognitive/grey matter, motor/white matter, and visual. The scoring system also included stage of myelination and presence of punctate hemorrhages. The correlation of individual and total MRI scores with neurodevelopmental assessment using Bayley Scales for Infant and Toddler Development- version 3 (BSID III) were examined via logistic regression models while controlling for confounding variables. RESULT: Median (IQR) MRI score was 6 (4-7) with grey matter score of 2 (1-4). Initial BSID III scores were 80 ± 15, 80 ± 18, and 81 ± 19 for cognitive, motor and language components, respectively. The MRI cognitive score had direct correlation with respiratory index prior to surgery (cc = 0.47, p = 0.03) and cross-clamping time (cc = 0.65, p = 0.001). It displayed a significant inverse correlation with language scores for BSID III at 9 months (R = -0.42, p = 0.04) which lost significance in subsequent visits. CONCLUSION: This pilot study proved the feasibility of correlating structural brain abnormalities in MRI with later brain developmental deficits in infants with CHD. We envision establishing a standardized MRI scoring system to be performed on a large multi-center cohort that would help better predict and measure brain injury in infants with CHDs.

Predictors of cerebral arteriopathy in children with arterial ischemic stroke: results of the International Pediatric Stroke Study.

BACKGROUND: Cerebral arteriopathies, including an idiopathic focal cerebral arteriopathy of childhood (FCA), are common in children with arterial ischemic stroke and strongly predictive of recurrence. To better understand these lesions, we measured predictors of arteriopathy within a large international series of children with arterial ischemic stroke. METHODS AND RESULTS: Between January 2003 and July 2007, 30 centers within the International Pediatric Stroke Study enrolled 667 children (age, 29 days to 19 years) with arterial ischemic stroke and abstracted clinical and radiographic data. Cerebral arteriopathy and its subtypes were defined using published definitions; FCA was defined as cerebral arterial stenosis not attributed to specific diagnoses such as moyamoya, arterial dissection, vasculitis, or postvaricella angiopathy. We used multivariate logistic regression techniques to determine predictors of arteriopathy and FCA among those subjects who received vascular imaging. Of 667 subjects, 525 had known vascular imaging results, and 53% of those (n=277) had an arteriopathy. The most common arteriopathies were FCA (n=69, 25%), moyamoya (n=61, 22%), and arterial dissection (n=56, 20%). Predictors of arteriopathy include early school age (5 to 9 years), recent upper respiratory infections, and sickle cell disease, whereas prior cardiac disease and sepsis reduced the risk of arteriopathy. The only predictor of FCA was recent upper respiratory infection. CONCLUSIONS: Arteriopathy is prevalent among children with arterial ischemic stroke, particularly those presenting in early school age, and those with a history of sickle cell disease. Recent upper respiratory infection predicted cerebral arteriopathy and FCA in particular, suggesting a possible role for infection in the pathogenesis of these lesions.

Arterial Ischemic Stroke Secondary to Cardiac Disease in Neonates and Children.

OBJECTIVE: We describe the risk factors for peri-procedural and spontaneous arterial ischemic stroke (AIS) in children with cardiac disease. METHODS: We identified children with cardiac causes of AIS enrolled in the International Pediatric Stroke Study registry from January 2003 to July 2014. Isolated patent foramen ovale was excluded. Peri-procedural AIS (those occurring during or within 72 hours of cardiac surgery, cardiac catheterization, or mechanical circulatory support) and spontaneous AIS that occurred outside of these time periods were compared. RESULTS: We identified 672 patients with congenital or acquired cardiac disease as the primary risk factor for AIS. Among these, 177 patients (26%) had peri-procedural AIS and 495 patients (74%) had spontaneous AIS. Among non-neonates, spontaneous AIS occurred at older ages (median 4.2 years, interquartile range 0.97 to 12.4) compared with peri-procedural AIS (median 2.4 years, interquartile range 0.35 to 6.1, P < 0.001). About a third of patients in both groups had a systemic illness at the time of AIS. Patients who had spontaneous AIS were more likely to have a preceding thrombotic event (16 % versus 9 %, P = 0.02) and to have a moderate or severe neurological deficit at discharge (67% versus 33%, P = 0.01) compared to those with peri-procedural AIS. CONCLUSIONS: Children with cardiac disease are at risk for AIS at the time of cardiac procedures but also outside of the immediate 72 hours after procedures. Many have acute systemic illness or thrombotic event preceding AIS, suggesting that inflammatory or prothrombotic conditions could act as a stroke trigger in this susceptible population.

Congenital glioneuronal tumor with neuropil-like islands.

The glioneuronal tumor with neuropil-islands is considered a rare variant of an astrocytoma. Congenital cases of glioneuronal tumor with neuropil-islands, which typically arise in adults, have not been reported to our knowledge. We report an autopsy case of an in-utero demise of a 38-week-gestation female fetus in a 29-year-old female. At autopsy, a previously detected supratentorial tectal mass (by fetal MRI) was identified. Histology showed a biphasic neoplasm marked by island of gray matter-like parenchyma rimmed by mature-appearing neuronal cells intermixed with variably cellular areas resembling a low grade astrocytoma. Focally, the tumor was noted to involve the overlying meninges. The neuronal cell components were highlighted with synaptophysin and neuN antibodies and the glioma areas stained with glial fibrillary acidic protein antibody. The tumor did not stain with isocitrate dehydrogenase 1 (R132H) antibody and had a low Ki-67 labeling index (1.4%), in keeping with a low grade tumor. The pathologic findings were interpreted as representing a low grade glioneuronal tumor with neuropil-like islands. There have been few reports of this tumor arising in children, with most of those developing in the spinal cord. To our knowledge, this is the first reported congenital case of this tumor described in the literature.

Muscle biopsy findings in a child with NALCN gene mutation.

Mutation in NALCN (Sodium leak channel, non-selective) gene in humans has been shown to present with a wide spectrum of clinical manifestations including neurodevelopmental impairment, hypotonia and congenital contractures. Distinctive features including episodic ataxia and neuroaxonal dystrophy have also been reported. In this case report, we describe the muscle biopsy findings of a 3-year-old boy who presented with congenital arthrogryposis, hypotonia and developmental delay who has a heterozygous de novo C.965T>C (p.1332T) variant in the NALCN gene found by expanded whole exome sequencing (WES). Distal arthrogryposis and ulnar deviation of hands were prominent findings, which have been shown to be associated with de novo heterozygous mutations in this gene. He also presented with brief paroxysmal episodes of tremulousness; however, he has not clearly had episodes of episodic ataxia. Initial work-up including extensive genetic and metabolic tests was normal except for mildly elevated multiple metabolites in urine, suggestive of mild dysfunction of multiple mitochondrial enzymes. Muscle biopsy findings revealed ragged red fiber changes on trichrome staining and an increased number of mitochondria with non-specific crystalloid like inclusions ultrastructurally. The biochemical and muscle biopsy findings are suggestive of a possible mitochondrial bioenergetic dysfunction. The association of NALCN gene with secondary mitochondrial dysfunction remains unclear.

Preparing for a "Pediatric Stroke Alert".

BACKGROUND: Childhood arterial ischemic stroke is an important cause of morbidity and mortality in children. Hyperacute treatment strategies remain controversial and challenging, especially in the setting of increasingly proven medical and endovascular options in adults. Although national and international pediatric guidelines have given initial direction about acute therapy and management, pediatric centers have traditionally lacked the infrastructure to triage, diagnose, and treat childhood arterial ischemic stroke quickly. METHODS: In the past 10 years, researchers in the International Pediatric Stroke Study and Thrombolysis in Pediatric Stroke study have initiated early strategies for establishing pediatric specific stroke alerts. RESULTS: We review the rationale, process and components necessary for establishing a pediatric stroke alert. CONCLUSION: Development of pediatric stroke protocols and pathways, with evidence-based acute management strategies and supportive care where possible, facilitates the evaluation, management, and treatment of an acute pediatric stroke.

Oxidative phosphorylation analysis: assessing the integrated functional activity of human skeletal muscle mitochondria--case studies.

Oxidative phosphorylation analysis, performed on freshly-isolated mitochondria, assesses the integrated function of the electron transport chain (ETC) coupled to ATP synthesis, membrane transport, dehydrogenase activities, and the structural integrity of the mitochondria. In this review, a case study approach is employed to highlight detection of defects in the adenine nucleotide translocator, the pyruvate dehydrogenase complex, fumarase, coenzyme Q function, fatty acid metabolism, and mitochondrial membrane integrity. Our approach uses the substrates glutamate, pyruvate, 2-ketoglutarate (coupled with malonate), malate, and fatty acid substrates (palmitoylcarnitine, octanoylcarnitine, palmitoyl-CoA (with carnitine), octanoyl-CoA (with carnitine), octanoate and acetylcarnitine) in addition to succinate, durohydroquinone and TMPD/ascorbate to uncover metabolic defects that would not be apparent from ETC assays performed on detergent-solubilized mitochondria.

Cardiac transplantation in twins with autosomal dominant Emery-Dreifuss muscular dystrophy.

Emery-Dreifuss muscular dystrophy (EDMD) is a neuromuscular disorder resulting in progressive muscle weakness, contractures, and cardiomyopathy. We report successful cardiac transplantation in identical twin brothers with autosomal dominant EDMD, complicated by ventricular arrhythmias and end-stage cardiomyopathy. Early recognition of progressive cardiac disease and subsequent cardiac transplantation are lifesaving in children with EDMD.

Cerebral vasculopathy in children with neurofibromatosis type 1.

Cerebral vasculopathy is an important but underrecognized complication of neurofibromatosis type 1. Over a 10-year period, we retrospectively assessed the prevalence, clinical manifestations, management, and outcome of cerebral vasculopathy in children with neurofibromatosis type 1. Magnetic resonance imaging (MRI) of the brain was performed on 78% of the patients (312/398) of which 46% (143/312) had magnetic resonance angiography of the intracranial arteries; 4.8% (15/312) had cerebral vasculopathy. Approximately half were asymptomatic at presentation; none had neurologic deficits. Cerebral vasculopathy included moyamoya changes (7) and stenosis/occlusion of major intracranial arteries (8). On follow-up (mean 4 years), 2 patients developed radiologic progression; 1 was treated with aspirin alone, whereas another underwent revascularization surgery. Although cerebral vasculopathy in neurofibromatosis type 1 may be asymptomatic at presentation, there may be radiologic and clinical progression leading to morbidity and mortality. Magnetic resonance angiography should be considered with brain MRI for early detection and timely intervention of cerebral vasculopathy.

Tuberculous radiculomyelitis presenting in a toddler with lower extremity weakness and seizure.

Tuberculous radiculomyelitis is an uncommon but serious complication of tuberculosis that can lead to considerable morbidity and mortality. We present the case of a 21-month-old male Congolese refugee diagnosed with tuberculous radiculomyelitis who presented with gradual motor and speech regression, and likely an infection-related seizure 2 months before diagnosis.

Neonatal stroke and progressive leukoencephalopathy in a child with an ACTA2 mutation.

Mutations in the smooth muscle-specific isoform of α-actin (ACTA2) cause vascular smooth muscle dysfunction leading to aortic aneurysm and moyamoya syndrome. A unique R179H mutation in ACTA2 has been reported to result in widespread smooth muscle dysfunction affecting vascular and extravascular smooth muscles. We report a 7-year-old girl with an ACTA2 R179H mutation manifesting with neonatal seizures due to multifocal infarcts, asymmetric motor deficits, global developmental delay, spasticity, congenital bilateral mydriasis, and a large patent ductus arteriosus. Serial magnetic resonance imaging (MRI) of the brain over 7 years showed diffuse supratentorial white matter abnormalities consistent with a progressive leukoencephalopathy. Magnetic resonance angiography of the cerebral vessels showed stenosis in the terminal portion of the bilateral internal carotid arteries with fusiform dilation of the proximal segment. Neonatal onset of neurologic symptoms in ACTA2 mutations has not been previously reported. R179H mutation in ACTA2 represents the severe end of the disease spectrum.

'Double trouble': diagnostic challenges in Duchenne muscular dystrophy in patients with an additional hereditary skeletal dysplasia.

Duchenne muscular dystrophy (DMD) is caused by mutations in Dystrophin and affects 1 in 3600-6000 males. It is characterized by progressive weakness leading to loss of ambulation, respiratory insufficiency, cardiomyopathy, and scoliosis. We describe the unusual phenotype of 3 patients with skeletal dysplasias in whom an additional diagnosis of DMD was later established. Two unrelated boys presented with osteogenesis imperfecta due to point mutations in COL1A1 and were both subsequently found to have a 1 bp frameshift deletion in the Dystrophin gene at age 3 and age 15 years, respectively. The third patient had a diagnosis of pseudoachondroplasia caused by a mutation in the COMP gene and was found to have a deletion of exons 48-50 in Dystrophin at age 9. We discuss the atypical presentation caused by the concomitant presence of 2 conditions affecting the musculoskeletal system, emphasizing aspects that may confound the presentation of a well-characterized disease like DMD. Additional series of patients with DMD and a secondary inherited condition are necessary to establish the natural history in this "double trouble" population. The recognition and accurate diagnosis of patients with two independent genetic disease processes is essential for management, prognosis, genetic risk assessment, and discussion regarding potential therapeutic interventions.