Homozygous missense variants in YKT6 result in loss of function and are associated with developmental delay, with or without severe infantile liver disease and risk for hepatocellular carcinoma

PURPOSE

YKT6 plays important roles in multiple intracellular vesicle trafficking events but has not been associated with Mendelian diseases.

METHODS

We report three unrelated individuals with rare homozygous missense variants in YKT6 who exhibited neurological disease with or without a progressive infantile liver disease. We modeled the variants in Drosophila. We generated wild-type and variant genomic rescue constructs (GRs) of the fly ortholog dYkt6 and compared their ability in rescuing the loss-of-function phenotypes in mutant flies. We also generated a dYkt6KozakGAL4 allele to assess the expression pattern of dYkt6.

RESULTS

Two individuals are homozygous for YKT6 [NM_006555.3:c.554A>G p.(Tyr185Cys)] and exhibited normal prenatal course followed by failure to thrive, developmental delay and progressive liver disease. Haplotype analysis identified a shared homozygous region flanking the variant, suggesting a common ancestry. The third individual is homozygous for YKT6 [NM_006555.3:c.191A>G p.(Tyr64Cys)] and exhibited neurodevelopmental disorders and optic atrophy. Fly dYkt6 is essential and is expressed in the fat body (analogous to liver) and central nervous system. Wild-type GR can rescue the lethality and autophagic flux defects whereas the variants are less efficient in rescuing the phenotypes.

CONCLUSION

The YKT6 variants are partial loss-of-function alleles and the p.(Tyr185Cys) is more severe than p.(Tyr64Cys).

Novel Pathogenic DNAH5 Variants in Primary Ciliary Dyskinesia: Association with Visceral Heterotaxia and Neonatal Cholestasis

The dynein axonemal heavy chain 5 gene codes for a subunit of axonemal dynein necessary for ciliary motor function. Though research has elucidated the consequences of some variants in this gene, it is still unclear whether many variants in the DNAH5 locus are benign or pathogenic due to the rarity of primary ciliary dyskinesia (PCD, of which Kartagener's syndrome is a subset). Here, we introduce the case of an infant boy presenting with the classical findings of PCD along with visceral heterotaxia and neonatal cholestasis. Genetic testing indicated that the patient is a compound heterozygote with a pathogenic c.8498G > A (known as pathogenic) on the maternally derived allele and two variants of uncertain significance, c.1206T > A and c.7800T > G, on the paternally derived allele. As PCD is autosomal recessive, we conclude that one, or both, of these paternally derived variants are pathogenic. To our knowledge, this is the first time that the clinical implications of c.1206T > A (p.Asn402Lys) and c.7800T > G (p.Ile2600Met) are documented. Furthermore, we use this case as an example to recommend clinicians to assess for PCD and laterality defects when presented with severe infantile cholestasis. While the association of cholestasis with PCD is relatively uncommon, PCD is a risk factor for increased prevalence of biliary atresia and infections, both of which are known causes of cholestasis in early infancy.

Biliary Atresia Remnants Revisited: Myogenesis, Hepatic Duct-Like Structures, and Fate of Peribiliary Glands

PURPOSE AND CONTEXT

Proximal levels of excised remnants from youngest infants may reveal early features of biliary atresia (BA).

METHOD

A targeted IHC survey was applied to 34 most proximal 2 levels in 17 BA remnants excised at age 10-74 days including 7 = <30 days old and 6 control hepatic ducts (HD).

KEY RESULTS

Severity of inflammation and extent of active fibroplasia do not distinguish proximal remnants in younger (n = 7) and older (n = 10) infants. In 27/34 levels of 14/17 remnants, reactive stroma is focally SM-MHC-2 (+), marking smooth muscle myosin, termed reactive myogenesis (RM), that is absent in controls. RM facilitates identification of 3 novel hepatic duct remnants (HDR): an HD-like collagen collar lined by degenerating cholangiocytes (n = 5); erosion defects in loose reactive stroma (n = 14); solitary foci of hyperplastic squamoid epithelium (n = 4). Peribiliary glands are either hyperplastic or atretic and typically lack RM.

CONCLUSION

Minimally inflammed end-stage lesions in BA remnants occur at youngest ages favoring prenatal onset. Three novel HDR are defined. RM, a useful surrogate for HDR, is a prevalent inappropriate stromal reaction in proximal remnants of uncertain biological significance. RM is the source of mature smooth muscle in BA remnants.

Stx4 is required to regulate cardiomyocyte Ca2+ handling during vertebrate cardiac development

Requirements for vesicle fusion within the heart remain poorly understood, despite the multitude of processes that necessitate proper intracellular trafficking within cardiomyocytes. Here, we show that Syntaxin 4 (STX4), a target-Soluble N-ethylmaleimide sensitive factor attachment receptor (t-SNARE) protein, is required for normal vertebrate cardiac conduction and vesicular transport. Two patients were identified with damaging variants in STX4. A patient with a homozygous R240W missense variant displayed biventricular dilated cardiomyopathy, ectopy, and runs of non-sustained ventricular tachycardia, sensorineural hearing loss, global developmental delay, and hypotonia, while a second patient displayed severe pleiotropic abnormalities and perinatal lethality. CRISPR/Cas9-generated stx4 mutant zebrafish exhibited defects reminiscent of these patients' clinical presentations, including linearized hearts, bradycardia, otic vesicle dysgenesis, neuronal atrophy, and touch insensitivity by 3 days post fertilization. Imaging of Vamp2+ vesicles within stx4 mutant zebrafish hearts showed reduced docking to the cardiomyocyte sarcolemma. Optical mapping of the embryonic hearts coupled with pharmacological modulation of Ca²⁺ handling together support that zebrafish stx4 mutants have a reduction in L-type Ca²⁺ channel modulation. Transgenic overexpression of zebrafish Stx4^R241W, analogous to the first patient's STX4^R240W variant, indicated that the variant is hypomorphic. Thus, these data show an in vivo requirement for SNAREs in regulating normal embryonic cardiac function and that variants in STX4 are associated with pleiotropic human disease, including cardiomyopathy.

Hypoplasia of Extrahepatic Biliary Tree and Intrahepatic Cholangiolopathy in Cystic Fibrosis Imperfectly Mimic Biliary Atresia in 4 Infants With Cystic Fibrosis and Kasai Portoenterostomy

Four male infants with cystic fibrosis and prolonged neonatal jaundice underwent Kasai procedure to relieve biliary obstruction due to apparent biliary atresia. The excised remnants had viscid mucus accumulation in hypoplastic gallbladders and distended peribiliary glands. Main hepatic ducts were narrow and/or malformed. Microscopic differences between the gallbladder and extrahepatic bile ducts in cystic fibrosis and sporadic biliary atresia were unequivocal, despite some histologic overlap; no erosive or fibro-obliterative lesions typical of biliary atresia were seen. Common in liver, biopsies were small duct cholangiopathy with intense focal cholangiolitis and massive accumulation of ceroid pigment within damaged cholangiocytes, and in portal macrophages, portal fibrosis, and unequivocal features of large duct obstruction were inconspicuous compared with biliary atresia. Plugs of bile in small ducts tended to be pale and strongly periodic acid-Schiff-reactive in cystic fibrosis. Distinguishing the liver lesion from that of biliary atresia is challenging but possible. Liver biopsies from 2 additional infants with cystic fibrosis and prolonged jaundice that spontaneously resolved showed a similar small duct cholangiopathy. Small gallbladders and extrahepatic ducts challenge surgical judgment as findings in liver biopsies challenge the pathologist. The decision to perform a Kasai procedure is reasonable when mimicry of biliary atresia is grossly complete. We hypothesize that a disorder of bile volume/flow during development and/or early infancy linked to the CFTR mutation alone or in combination with the stresses of neonatal intensive care causes destructive cholangiolitis and intrahepatic reduction of bile flow with secondary hypoplasia of extrahepatic biliary structures.

Congenital Portosystemic Shunts in Children: Associations, Complications, and Outcomes

BACKGROUND

Congenital portosystemic shunt (CPSS) is a rare malformation in which splanchnic venous flow bypasses the liver. CPSS is associated with other congenital anomalies and syndromes and can be associated with life-threatening complications. CPSS and their management remain underreported in the literature. Here, we review the clinical characteristics, management, and outcomes of a cohort of children and young adults with CPSS from two pediatric centers.

METHODS

Cases of CPSS from Cincinnati Children's Hospital Medical Center and C.S. Mott Children's Hospital were reviewed to define CPSS anatomy, associated anomalies, complications, interventions, and outcomes. The imaging features and histopathology of liver lesions were characterized in detail.

RESULTS

A total of 11 cases were identified. Median age was 10 years (range 0-26); 8 (73%) cases were female. Associated anomalies included six patients with heterotaxy (55%), five patients with congenital heart disease (45%), three patients with Turner syndrome (27%), and two patients with omphalocele, exstrophy, imperforate anus, spinal defects (OEIS) complex (18%). Eight (73%) cases had hyperammonemia ± encephalopathy. A 4-month-old presented with hepatopulmonary syndrome, and 12-year-old presented with pulmonary hypertension. Eight patients (73%) had liver lesions including five with premalignant adenomas and three with well-differentiated hepatocellular carcinoma (HCC). Four children underwent successful CPSS occlusion/ligation. Three children underwent liver transplant (2) or resection (1) for HCC without recurrence at extended follow-up.

CONCLUSIONS

CPSS is associated with multiple anomalies (heterotaxy, congenital heart disease) and syndromes (Turner syndrome). CPSS liver lesions should be very carefully evaluated due to risk of premalignant adenomas and HCC. Serious complications of CPSS can occur at a young age but can be managed endovascularly or with open surgery.

Inborn Errors of Bile Acid Metabolism

Inborn errors of bile acid metabolism are rare causes of neonatal cholestasis and liver disease in older children and adults. The diagnosis should be considered in the context of hyperbilirubinemia with normal serum bile acids and made by urinary liquid secondary ionization mass spectrometry or DNA testing. Cholic acid is an effective treatment of most single-enzyme defects and patients with Zellweger spectrum disorder with liver disease.

Large-scale proteomics identifies MMP-7 as a sentinel of epithelial injury and of biliary atresia

Biliary atresia is a progressive infantile cholangiopathy of complex pathogenesis. Although early diagnosis and surgery are the best predictors of treatment response, current diagnostic approaches are imprecise and time-consuming. We used large-scale, quantitative serum proteomics at the time of diagnosis of biliary atresia and other cholestatic syndromes (serving as disease controls) to identify biomarkers of disease. In a discovery cohort of 70 subjects, the lead biomarker was matrix metalloproteinase-7 (MMP-7), which retained high distinguishing features for biliary atresia in two validation cohorts. Notably, the diagnostic performance reached 95% when MMP-7 was combined with γ-glutamyltranspeptidase (GGT), a marker of cholestasis. Using human tissue and an experimental model of biliary atresia, we found that MMP-7 is primarily expressed by cholangiocytes, released upon epithelial injury, and promotes the experimental disease phenotype. Thus, we propose that serum MMP-7 (alone or in combination with GGT) is a diagnostic biomarker for biliary atresia and may serve as a therapeutic target.

Long-Term Cholic Acid Therapy in Zellweger Spectrum Disorders

Zellweger spectrum disorders (ZSDs), a subgroup of peroxisomal biogenesis disorders, have a generalized defect in peroxisome function. Liver disease in ZSDs has been linked to accumulation of C₂₇-bile acid intermediates due to the lack of peroxisomal β-oxidation of these intermediates to form primary C₂₄-bile acids. Oral treatment with primary bile acid, cholic acid (CA), inhibits formation of hepatotoxic C₂₇-bile acids by restoring normal physiologic feedback inhibition on bile acid synthesis. We present the long-term CA treatment and liver-related outcomes for 3 pediatric patients with ZSDs who have received CA treatment for ≥15 years. Ongoing CA treatment was associated with stabilized liver function, as shown by serum biochemistries and liver histopathology, and no treatment-related adverse effects were observed. All 3 patients have attended regular school with classroom accommodations and attained a good quality of life. Our patient outcomes suggest that early and ongoing CA therapy may sustain liver function in patients with ZSDs.

Zebrafish abcb11b mutant reveals strategies to restore bile excretion impaired by bile salt export pump deficiency

Bile salt export pump (BSEP) adenosine triphosphate-binding cassette B11 (ABCB11) is a liver-specific ABC transporter that mediates canalicular bile salt excretion from hepatocytes. Human mutations in ABCB11 cause progressive familial intrahepatic cholestasis type 2. Although over 150 ABCB11 variants have been reported, our understanding of their biological consequences is limited by the lack of an experimental model that recapitulates the patient phenotypes. We applied CRISPR/Cas9-based genome editing technology to knock out abcb11b, the ortholog of human ABCB11, in zebrafish and found that these mutants died prematurely. Histological and ultrastructural analyses showed that abcb11b mutant zebrafish exhibited hepatocyte injury similar to that seen in patients with progressive familial intrahepatic cholestasis type 2. Hepatocytes of mutant zebrafish failed to excrete the fluorescently tagged bile acid that is a substrate of human BSEP. Multidrug resistance protein 1, which is thought to play a compensatory role in Abcb11 knockout mice, was mislocalized to the hepatocyte cytoplasm in abcb11b mutant zebrafish and in a patient lacking BSEP protein due to nonsense mutations in ABCB11. We discovered that BSEP deficiency induced autophagy in both human and zebrafish hepatocytes. Treatment with rapamycin restored bile acid excretion, attenuated hepatocyte damage, and extended the life span of abcb11b mutant zebrafish, correlating with the recovery of canalicular multidrug resistance protein 1 localization.

CONCLUSIONS

Collectively, these data suggest a model that rapamycin rescues BSEP-deficient phenotypes by prompting alternative transporters to excrete bile salts; multidrug resistance protein 1 is a candidate for such an alternative transporter. (Hepatology 2018;67:1531-1545).

Infant Mortality, Cause of Death, and Vital Records Reporting in Ohio, United States

Introduction Infant mortality rate is a sensitive metric for population health and well-being. Challenges in achieving accurate reporting of these data can lead to inaccurate targeting of public health interventions. We analyzed a cohort from a pediatric tertiary care referral medical center to evaluate concordance between autopsy cause of death (COD) and death certificate documentation for infants <1 year of age. We predicted that infant COD as documented through vital records would not correspond to that as determined by autopsy. Methods We conducted a retrospective review comparing causes of infant death reported through Ohio Department of Health documents to those on Cincinnati Children's Hospital Medical Center autopsy reports over an 8-year period from January 1, 2006 through December 31, 2013. Results We analyzed 276 total cases of which 167 (61.5 %) represented infants born preterm. Autopsy reports identified 55 % of cases had a congenital anomaly. Additionally, 34 % of all cases had primary or contributing COD related to infection and 14.5 % of all cases indicated chorioamnionitis. We identified 156 (56.5 %) death certificates discordant with autopsy COD of which 52 (33.3 %) involved infection and 24 (15.4 %) involved congenital anomalies. Discussion There are opportunities to improve COD reporting through training for providers, and improvement of established state certification systems. Future strategies to reduce infant mortality will be better informed through enhancements in vital records COD reporting.

Hepatic Hilar Lymph Node Reactivity at Kasai Portoenterostomy for Biliary Atresia: Correlations With Age, Outcome, and Histology of Proximal Biliary Remnant

We hypothesized that if infection is the proximate cause of congenital biliary atresia, an appropriate response to antigen would occur in lymph nodes contiguous with the biliary remnant. We compared the number of follicular germinal centers (GC) in 79 surgically excised hilar lymph nodes (LN) and 27 incidentally discovered cystic duct LNs in 84 subjects at the time of hepatic portoenterostomy (HPE) for biliary atresia (BA) to autopsy controls from the pancreaticobiliary region of non-septic infants >3 months old at death. All 27 control LN lacked GC, a sign in infants of a primary response to antigenic stimulation. GC were found in 53% of 106 LN in 56 of 84 subjects. Visible surgically excised LN contiguous with the most proximal biliary remnants had 1 or more well-formed reactive GC in only 26/51 subjects. Presence of GC and number of GC/LN was unrelated to age at onset of jaundice or to active fibroplasia in the biliary remnant but was related to older age at HPE. Absent GC in visible and incidentally removed cystic duct LNs predicted survival with the native liver at 2 and 3 years after HPE, P = .03, but significance was lost at longer intervals. The uncommon inflammatory lesions occasionally found in remnants could be secondary either to bile-induced injury or secondary infection established as obstruction evolves. The absence of consistent evidence of antigenic stimulation in LN contiguous with the biliary remnant supports existence of at least 1 major alternative to infection in the etiology of biliary atresia.

Two Case Reports of FGF23-Induced Hypophosphatemia in Childhood Biliary Atresia

Cholestatic liver disease has long been associated with childhood rickets, secondary to impaired absorption of fat-soluble vitamin D. Elevated serum levels of fibroblast growth factor 23 (FGF23), secondary to genetic defects or tumor-induced osteomalacia, causes hypophosphatemic rickets in childhood. We present 2 infants with end-stage liver disease due to biliary atresia (BA) who developed hypophosphatemia with renal phosphate wasting. Serum FGF23 levels were elevated more than 8 times the upper limit of normal, and the older infant showed radiographic evidence of rickets. Both infants required large supplements of phosphate in addition to calcitriol. Following liver transplantation, FGF23 normalized in both patients and phosphate and calcitriol supplementation were discontinued. Immunohistochemistry revealed ectopic overexpression of FGF23 by hepatocytes in the BA liver. These observations highlight a unique cause of hypophosphatemic rickets in childhood and suggest the need for further investigation into the relationship between BA and other cholestatic disorders, and bone metabolism.

Calretinin-Immunoreactive Hypoinnervation in Down Syndrome (DS): Report of an Infant with Very Short-Segment Hirschsprung Disease and Comparison to Biopsy Findings in 20 Normal Infants and 11 Infants with DS and Chronic Constipation

In Down syndrome (DS) constipation is common, and the incidence of Hirschsprung disease (HD) is 1-2%. Rectal suction biopsies (RSBs) in DS may show discordant features; calretinin immunoreactivity (CRir) often helps resolve discrepancies. We report a case of unequivocal very short-segment HD (vsHD) in an infant with DS who had aganglionosis with abnormal acetylcholine esterase (AChE) activity in 3 RSBs. The CRir patterns were scanty positive rather than the expected absent CRir innervation in the lamina propria (LP). The resection specimen was grossly typical for short-segment HD, with a 5.5-cm, narrow but normally ganglionated segment proximal to the verified very short distal anganglionic zone. Unequivocal calretinin hypoinnervation was limited to the distal 2 cm, substantiating the warning of Kapur that small numbers of CRir nerves in the LP do not exclude a diagnosis of vsHD. We evaluated RSBs from 11 DS and 20 randomly selected normal infants <6 months of age with chronic constipation. The normal infants had abundant mucosal calretinin innervation and AChE histochemistry. We observed variable CRir hypoinnervation in RSBs in DS infants (including 6/7 with "normal" original diagnosis and 1/4 with HD). Our findings caution against overdependence on "normal" calretinin immunohistochemistry and suggest that AChE may be more reliable than CRir in the context of DS. An unknown number of patients with DS may have enteric nervous system disorders functionally similar to HD, which are possibly related to abnormal or imbalanced autonomic innervation, of which distal calretinin hypoinnervation is one manifestation, despite the presence of ganglia.

Early-lethal Costello syndrome due to rare HRAS Tandem Base substitution (c.35_36GC>AA; p.G12E)-associated pulmonary vascular disease

Costello syndrome is a rare, autosomal-dominant syndrome caused by activating missense mutations in the Harvey rat sarcoma viral oncogene homolog (HRAS), most often p.G12S. Several rare mutations have consistently been associated with a more severe phenotype that is often lethal in infancy. Cause of death is most often respiratory failure, with hypertrophic cardiomyopathy playing a significant role in morbidity. Impaired fibroblast elastogenesis is thought to contribute to the Costello phenotype, but reports of histologic evidence of disordered elastogenesis at autopsy are limited. We report a patient with Costello syndrome due to a rare tandem base substitution (c.35_36GC>AA) resulting in the p.G12E missense change. The proband died at the age of 3 months from respiratory failure, with minimal evidence of cardiomyopathy. The autopsy disclosed pulmonary vascular dysplasia affecting small arteries and veins associated with abnormal elastin distribution in tortuous dilated arteries and veins, with nonuniform wall thickness and semiobstructive lesions at artery branch points typical of early pulmonary hypertensive vascular disease. Elastic fibers in the dermis were abnormally short and fragmented. This case suggests that disordered elastogenesis in the pulmonary vasculature and undiagnosed (or underdiagnosed) pulmonary hypertension may contribute to morbidity in patients with Costello syndrome.

Extrahepatic anomalies in infants with biliary atresia: results of a large prospective North American multicenter study

The etiology of biliary atresia (BA) is unknown. Given that patterns of anomalies might provide etiopathogenetic clues, we used data from the North American Childhood Liver Disease Research and Education Network to analyze patterns of anomalies in infants with BA. In all, 289 infants who were enrolled in the prospective database prior to surgery at any of 15 participating centers were evaluated. Group 1 was nonsyndromic, isolated BA (without major malformations) (n = 242, 84%), Group 2 was BA and at least one malformation considered major as defined by the National Birth Defects Prevention Study but without laterality defects (n = 17, 6%). Group 3 was syndromic, with laterality defects (n = 30, 10%). In the population as a whole, anomalies (either major or minor) were most prevalent in the cardiovascular (16%) and gastrointestinal (14%) systems. Group 3 patients accounted for the majority of subjects with cardiac, gastrointestinal, and splenic anomalies. Group 2 subjects also frequently displayed cardiovascular (71%) and gastrointestinal (24%) anomalies; interestingly, this group had genitourinary anomalies more frequently (47%) compared to Group 3 subjects (10%).

CONCLUSION

This study identified a group of BA (Group 2) that differed from the classical syndromic and nonsyndromic groups and that was defined by multiple malformations without laterality defects. Careful phenotyping of the patterns of anomalies may be critical to the interpretation of both genetic and environmental risk factors associated with BA, allowing new insight into pathogenesis and/or outcome.

Validation of a score tool for measurement of histological severity in juvenile dermatomyositis and association with clinical severity of disease

Objectives

To study muscle biopsy tissue from patients with juvenile dermatomyositis (JDM) in order to test the reliability of a score tool designed to quantify the severity of histological abnormalities when applied to biceps humeri in addition to quadriceps femoris. Additionally, to evaluate whether elements of the tool correlate with clinical measures of disease severity.

Methods

55 patients with JDM with muscle biopsy tissue and clinical data available were included. Biopsy samples (33 quadriceps, 22 biceps) were prepared and stained using standardised protocols. A Latin square design was used by the International Juvenile Dermatomyositis Biopsy Consensus Group to score cases using our previously published score tool. Reliability was assessed by intraclass correlation coefficient (ICC) and scorer agreement (α) by assessing variation in scorers’ ratings. Scores from the most reliable tool items correlated with clinical measures of disease activity at the time of biopsy.

Results

Inter- and intraobserver agreement was good or high for many tool items, including overall assessment of severity using a Visual Analogue Scale. The tool functioned equally well on biceps and quadriceps samples. A modified tool using the most reliable score items showed good correlation with measures of disease activity.

Conclusions

The JDM biopsy score tool has high inter- and intraobserver agreement and can be used on both biceps and quadriceps muscle tissue. Importantly, the modified tool correlates well with clinical measures of disease activity. We propose that standardised assessment of muscle biopsy tissue should be considered in diagnostic investigation and clinical trials in JDM.

Abstract 520: Elastic Fiber Fragmentation and Aberrant Angiogenesis Precede Inflammation in Early-Onset Aortic Valve Disease

Introduction

Elastic fiber fragmentation (EFF) is a hallmark of aortic valve disease (AVD), and both inflammation and neovascularization have been identified as late findings, presumably due to atherosclerosis through a wound healing like response. However, EFF independently stimulates angiogenesis, suggesting an alternative mechanism for neovascularization in AVD.

Hypothesis

We hypothesized that aberrant angiogenesis would be an early AVD finding, preceding inflammation, due to EFF.

Methods

To examine disease progression, valve tissue was examined using histochemistry and immunohistochemistry from early (<40yo) and late (≥40yo) onset AVD specimens, as well as age-matched autopsy control aortic valves. Angiogenesis (VEGF-A, CD-31, SMA and chondromodulin), EFF (elastin, fibrillin-1, emilin-1, fibulin-5), progenitor valve interstitial cell phenotype (CD-34, CD-45) and inflammation (CD-68, LRP-5) were assessed.

Results

Bicuspid aortic valve was more common in early-onset AVD (n=21), and cardiovascular comorbidities were more common in late-onset AVD (n=11). Early-onset AVD specimens demonstrated angiogenesis without inflammation or atherosclerosis. A distinct pattern of EFF and elastic fiber components surrounded early-onset AVD neovessels, which were not present in control valves, including increased emilin and decreased fibulin-5, and the elastase/anti-elastase ratio and localization were altered in both early and late-onset AVD, suggesting a dynamic disease progression. Interestingly, progenitor VICs were present in control valves at both stages and were unchanged in age-matched AVD specimens.

Conclusions

Aberrant angiogenesis is an early mechanism in AVD pathogenesis preceding inflammation, implicating EFF as an inciting factor. Elucidation of the underlying mechanisms may inform the development of new pharmacologic therapeutics and durable bioprostheses.

Genetic defects in bile acid conjugation cause fat-soluble vitamin deficiency

BACKGROUND & AIMS

The final step in bile acid synthesis involves conjugation with glycine and taurine, which promotes a high intraluminal micellar concentration to facilitate lipid absorption. We investigated the clinical, biochemical, molecular, and morphologic features of a genetic defect in bile acid conjugation in 10 pediatric patients with fat-soluble vitamin deficiency, some with growth failure or transient neonatal cholestatic hepatitis.

METHODS

We identified the genetic defect that causes this disorder using mass spectrometry analysis of urine, bile, and serum samples and sequence analysis of the genes encoding bile acid-CoA:amino acid N-acyltransferase (BAAT) and bile acid-CoA ligase (SLC27A5).

RESULTS

Levels of urinary bile acids were increased (432 ± 248 μmol/L) and predominantly excreted in unconjugated forms (79.4% ± 3.9%) and as sulfates and glucuronides. Glycine or taurine conjugates were absent in the urine, bile, and serum. Unconjugated bile acids accounted for 95.7% ± 5.8% of the bile acids in duodenal bile, with cholic acid accounting for 82.4% ± 5.5% of the total. Duodenal bile acid concentrations were 12.1 ± 5.9 mmol/L, which is too low for efficient lipid absorption. The biochemical profile was consistent with defective bile acid amidation. Molecular analysis of BAAT confirmed 4 different homozygous mutations in 8 patients tested.

CONCLUSIONS

Based on a study of 10 pediatric patients, genetic defects that disrupt bile acid amidation cause fat-soluble vitamin deficiency and growth failure, indicating the importance of bile acid conjugation in lipid absorption. Some patients developed liver disease with features of a cholangiopathy. These findings indicate that patients with idiopathic neonatal cholestasis or later onset of unexplained fat-soluble vitamin deficiency should be screened for defects in bile acid conjugation.

Rectal biopsy in children with Down syndrome and chronic constipation: Hirschsprung disease vs non-hirschsprung disease

Hirschsprung disease (HD) is reported in patients with Down syndrome with a frequency between 2% and 10%. The incidence of HD is 2% in our community-based registry that contains >700 patients with Down syndrome. We reviewed rectal biopsy findings in 32 of these patients who had suction rectal biopsy performed between 1980 and 2009 to investigate the cause of chronic constipation. We confirmed that 15 patients had diagnostic histologic and histochemical features of HD. More challenging were findings in 5 of 17 patients, in whom ganglia coexisted with equivocal acetylcholinesterase reaction patterns and/or hypertrophic submucosal nerves. In this retrospective study, we were able to resolve most of these discrepant findings by demonstrating normal calretinin-positive nerve twigs in the lamina propria and muscularis mucosae. The clinical significance of these unexpected findings in suction rectal biopsy specimens that did not satisfy strict criteria for a tissue diagnosis of HD is unknown. We speculate that a minority of these patients have transition zone morphology or an incomplete/atypical form of HD. Further investigations may help resolve discrepancies that arise when suction rectal biopsy is used to investigate chronic constipation in Down syndrome.

Importance of muscle light microscopic mitochondrial subsarcolemmal aggregates in the diagnosis of respiratory chain deficiency

The purpose of this study was to evaluate relationships between subsarcolemmal mitochondrial aggregates and electron transport chain deficiencies in skeletal muscle with the objective of establishing an association between mitochondrial accumulation and electron transport chain complex deficiency. We conducted a large-scale, retrospective study to evaluate factors associated with subsarcolemmal mitochondrial aggregates (percent) in pediatric patients who received muscle biopsies for suspected respiratory chain disorders. Patients were included if they had histochemical stains for assessment of mitochondrial pathology and had biochemical testing for muscle electron transport chain complex activities. Significant positive bivariate correlations (n = 337) were found between subsarcolemmal mitochondrial aggregate percentage and electron transport chain complexes II, IV, I + III, and II + III activities. Evaluation showed that a cutoff value of > 2% subsarcolemmal mitochondrial aggregates had poor overall diagnostic accuracy (mean, 32%), compared with a < 5% cutoff (mean, 60%). To better evaluate the effects of subsarcolemmal mitochondrial aggregates percentages, patients were stratified according to lower one-third (group 1, n = 120 plus ties) and upper one-third (group 2, n = 115 plus ties) of subsarcolemmal mitochondrial aggregates values. Although only minor clinical and pathologic differences were observed, group 1 participants had significantly lower electron transport chain complex activities than group 2 for all enzymes except complex III. Logistic regression showed over 2-fold greater odds of deficiency for electron transport chain complexes I + III (P = .01) and II + III (P = .03) for group 1 participants compared with group 2. We conclude that, contrary to the previous > 2.0% subsarcolemmal mitochondrial aggregates cutoff for respiratory chain disorder, patients with a low subsarcolemmal mitochondrial aggregates percentage (≤4%) are significantly more likely to have electron transport chain complex deficiency than patients with increased subsarcolemmal mitochondrial aggregates percentage (≥10%). This morphological approach for assessment of mitochondrial proliferation may assist clinicians to select further testing to rule out an electron transport chain complex deficiency in children by other methods, including direct biochemical testing of electron transport chain complex activities, measurement of muscle coenzyme Q10 content, or evaluation for a mitochondrial DNA depletion syndrome.

Design and validation of the biliary atresia research consortium histologic assessment system for cholestasis in infancy

BACKGROUND & AIMS

Pathologists participating in the National Institutes of Health-sponsored Biliary Atresia Research Consortium (BARC) developed and then evaluated a standardized system for histologic reporting of liver biopsies from infants with cholestasis.

METHODS

A set of 97 anonymous liver biopsy samples was sent to 10 pathologists at BARC centers. A semiquantitative scoring system that had 16 histologic features was developed and then used by the pathologists, who had no knowledge of clinical history, imaging results, or laboratory data. Interobserver agreement was evaluated statistically. Agreement on scoring of each feature and on the pathologists' diagnosis, compared with the final clinical diagnosis, was evaluated by using weighted kappa statistics.

RESULTS

There was moderate to substantial interobserver agreement in identification of bile plugs in ducts, giant-cell transformation, extramedullary hematopoiesis, and bile duct proliferation. The pathologists' diagnosis of obstruction in clinically proven cases of biliary atresia (BA) ranged from 79%-98%, with a positive predictive value of 90.7%. Histologic features that best predicted BA, on the basis of logistic regression, included bile duct proliferation, portal fibrosis, and absence of sinusoidal fibrosis (each P<.0001).

CONCLUSIONS

The BARC histologic assessment system identified features of liver biopsies from cholestatic infants, with good interobserver agreement, that might be used in diagnosis and determination of prognosis. The system diagnosed BA with a high level of sensitivity and identified infants with biliary obstruction with reasonable interobserver agreement. However, distinguishing between BA and disorders such as total parenteral nutrition-associated liver disease and alpha(1)-antitrypsin deficiency is not possible without adequate clinical information.

Leukocyte adhesion deficiency type 1 presenting with recurrent pyoderma gangrenosum and flaccid scarring

We report an 11-year-old boy with a longstanding history of recurrent pyoderma gangrenosum and abnormal wound healing who eventually developed a fatal invasive fungal infection. This article emphasizes the importance to consider leukocyte adhesion deficiency type 1 in the differential diagnosis of patients with recurrent skin ulcers.

A fetus with hypertrophic cardiomyopathy, restrictive, and single-ventricle physiology, and a beta-myosin heavy chain mutation

Cardiomyopathy is a significant clinical problem associated with sudden death. A molecular taxonomy is emerging that is refining the clinical classification system. We describe a patient with a pathogenic familial beta-myosin heavy chain mutation who was prenatally diagnosed with left ventricular hypoplasia and restrictive diastolic physiology.

Ductal plate malformation-like arrays in early explants after a Kasai procedure are independent of splenic malformation complex (heterotaxy)

Biliary atresia has at least 2 proposed forms, the common perinatal and the less common embryonic subtype with earlier onset and/or extrahepatic developmental anomalies. Histologic evidence of ductal plate malformation (DPM)-like change in liver has been proposed both as a marker for the embryonic type and as a predictor of poor outcome after Kasai portoenterostomy. We investigated the prevalence of DPM-like change in liver explants in usual biliary atresia (BA) and in BA with splenic malformation syndrome (BASM). Liver sections from 8 patients with BA and 6 with BASM, all of whom had a Kasai procedure followed by explant before age 2 years, were analyzed using hematoxylin and eosin, trichrome, CK7, and AE1/AE3 stains. Each block was scored for inflammation and fibrosis. We estimated the number of portal areas per block and counted the number of definite and possible examples of DPM-like change, defined as a circumferential duct complex arranged around a fibrovascular core. We assessed whether the frequency per portal area was related to low and high scores for either inflammation or fibrosis. Definite and possible examples of DPM-like arrays were present in about 10% of portal areas in both patient groups, but these were unevenly distributed. There was no statistical difference between BA and BASM in terms of the number of examples per portal area. No correlation existed between degree of fibrosis and the intensity of portal inflammation and the number of DPM-like arrays. Ductal plate malformation-like arrays do not distinguish perinatal BA from BA associated with heterotaxy in liver explants after a failed Kasai procedure.

Phenotypic and microscopic description of a new case of Ermine phenotype

We describe a new case of Ermine phenotype. The patient had the striking pattern of skin and hair involvement that characterize the condition, global developmental delay, growth retardation, microcephaly, and bilateral hearing loss. Results of extensive workup for several other neurologic, metabolic, mitochondrial, genetic and chromosomal conditions were normal. Microscopic examination demonstrated normal numbers of melanocytes and variable amounts of pigment depending on the degree of pigmentation in the region biopsied. Ultrastructure of melanosomes was abnormal suggesting a defect in melanin synthesis. Ermine phenotype has a distinct clinical presentation compared to other syndromes associated with abnormal pigment and deafness. Therefore, this should be included as an independent condition in the differential diagnosis. Additional phenotypic and pathologic descriptions are needed to better define this condition clinically, pathologically, and genetically.

Megalencephalic leukoencephalopathy with subcortical cysts: a third confirmed case with literature review

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) causes early-onset, slowly progressive central nervous system white matter disease, macrocephaly, and later cognitive and motor decline. We describe brain structure in a patient with MLC and proven MLC1 mutations. A male, normal at birth, had macrocephaly at 6 months followed by developmental delay. Magnetic resonance imaging showed extensive signal abnormality in cerebral white matter and subcortical progressive cystic changes in the bilateral temporal and right frontal areas. Biopsy of frontal gyrus at age 15 months showed normal gray matter. The subcortical white matter was pale due to prominent fine uniform 2- to 4-mu-thick vacuoles with a few interspersed myelinated axons and rare microglia. The vacuoles had a single-, double-, or, rarely, triple-unit membrane (resembling myelin) and contained occasional organelles but no intermediate filaments. Both normal myelinated and thinly myelinated axons were observed. The outer and occasionally the inner layers of myelin surrounding intact axons formed blebs that may represent a source for vacuoles. Genetic analysis identified 2 heterozygous mutations of intron 3 (c.322-1 G>A) and intron 7 (c.597+1G>A), the 1st leading to deletion of amino acids 60 to 89 and the 2nd to deletion of amino acids 194 to 199. Fine uniform vacuolation of white matter with wide separation of myelinated axons is the hallmark of MLC in early childhood.

Non-lethal congenital hypotonia due to glycogen storage disease type IV

Glycogen storage disease type IV (GSD-IV) is an autosomal recessive genetic disorder due to a deficiency in the activity of the glycogen branching enzyme (GBE). A deficiency in GBE activity results in the accumulation of glycogen with fewer branching points and long, unbranched outer chains. The disorder results in a variable phenotype, including musculoskeletal, cardiac, neurological, and hepatic involvement, alone or in continuum, which can be identified at any stage of life. The classic form of GSD-IV is a hepatic presentation, which presents in the first 18 months of life with failure to thrive, hepatomegaly, and cirrhosis that progresses to liver failure, resulting in death by age 5 years. A severe congenital musculoskeletal phenotype with death in the neonatal period has also been described. We report an unusual case of congenital musculoskeletal presentation of GSD-IV with stable congenital hypotonia, gross motor delay, and severe fibro-fatty replacement of the musculature, but no hepatic or cardiac involvement. Molecular analysis revealed two novel missense mutations with amino acid changes in the GBE gene (Q236H and R262C), which may account for the mild phenotype.

Concurrent course of transient neonatal diabetes with cholestasis and paucity of interlobular bile ducts: a case report

We report for the first time a patient with both transient neonatal diabetes mellitus (TNDM) and idiopathic neonatal cholestasis, with both features resolving over a similar time course. Cholestasis was due to paucity of interlobular bile ducts (PILBD). Genetic analysis was consistent with a uniparental disomy of chromosome 6. Paucity of interlobular bile ducts is common in Alagille syndrome but also occurs by unknown mechanisms in a wide spectrum of other diseases. We propose a shared explanation for this patient's TNDM and PILBD mediated by the noted chromosomal abnormality. We suggest that hepatobiliary function be evaluated in patients with TNDM to determine the prevalence and course of cholestasis of the disease.

Variability of acetylcholinesterase hyperinnervation patterns in distal rectal suction biopsy specimens in Hirschsprung disease

Variability in cholinergic innervation may contribute to false-negative and false-positive evaluations for Hirschsprung disease (HD). We compared intraspecimen variability of histochemical acetylcholinesterase (ACE) activity in 62 distal rectal mucosal biopsy specimens from 33 patients with short-segment HD (SSHD), 14 patients with short-segment HD/Down syndrome (SSHD/DS), 10 patients with total colonic aganglionosis (HDTC), and 45 ganglionated control specimens obtained because of clinical suspicion for HD. Specimens were evaluated in 1-mm linear segments for abnormal distribution and abnormal intensity of staining reaction in the lamina propria (LP), muscularis mucosae (MM), numerical excess of small submucosal nerves (SSN), and presence or absence of large submucosal nerves (LSN) defined as >35 microns in diameter. Patients with HD and controls were predominantly infant males. Aggregate length of specimens was 186 mm in HD and 136 mm in controls. We defined multiple patterns and relative frequencies of normal and abnormal ACE reactivity in the muscularis mucosae, submucosal nerves, and innervation in the lamina propria. We verified a hyperinnervation pattern more common in neonates within each subset of HD. Large submucosal nerves >35 microns in diameter are relatively less common in SSHD/DS and HDTC. Eleven of 57 patients with HD had at least 1 mm of normal muscularis mucosae accounting for 19/186 mm examined. Ten percent of control mm had at least 1 submucosal nerve >35 microns in diameter. Intraspecimen variability in ACE patterns, when extreme, can usually be resolved by findings elsewhere in an adequate specimen, minimizing the need for repeat procedures.

Mechanisms of disease: Inborn errors of bile acid synthesis

Inborn errors of bile acid synthesis are rare genetic disorders that can present as neonatal cholestasis, neurologic disease or fat-soluble-vitamin deficiencies. There are nine known defects of bile acid synthesis, including oxysterol 7alpha-hydroxylase deficiency, Delta(4)-3-oxosteroid-5beta-reductase deficiency, 3beta-hydroxy-Delta(5)-C(27)-steroid dehydrogenase deficiency, cerebrotendinous xanthomatosis (also known as sterol 27-hydroxylase deficiency), alpha-methylacyl-CoA racemase deficiency, and Zellweger syndrome (also known as cerebrohepatorenal syndrome). These diseases are characterized by a failure to produce normal bile acids and an accumulation of unusual bile acids and bile acid intermediaries. Individuals with inborn errors of bile acid synthesis generally present with the hallmark features of normal or low serum bile acid concentrations, normal gamma-glutamyl transpeptidase concentrations and the absence of pruritus. Failure to diagnose any of these conditions can result in liver failure or progressive chronic liver disease. If recognized early, many patients can have a remarkable clinical response to oral bile acid therapy.

False negative histochemical reaction for myophosphorylase activity in fulminant sepsis due to methicillin resistant Staphylococcus aureus

We report a false negative histochemical reaction for myophosphorylase in the case of an 11 year old with fulminant Staphylococcus aureus. Due to increased creatine kinase levels and marked myoglobinuria a muscle biopsy was performed prior to death. The biopsy revealed rhabdomyolysis, glycogen depletion and absent myophosphorylase reactivity. Subsequent myophosphorylase quantification was normal. This unique case of a false negative myophosphorylase histochemical reaction is apparently related to sepsis.

International consensus on a proposed score system for muscle biopsy evaluation in patients with juvenile dermatomyositis: A tool for potential use in clinical trials

OBJECTIVE

To devise and test a system with which to evaluate abnormalities on muscle biopsy samples obtained from children diagnosed with juvenile dermatomyositis (DM).

METHODS

We established an International Consensus Group on Juvenile DM Biopsy and carried out 2 phases of consensus process and scoring workshops. Biopsy sections (n = 33) were stained by standard methods. The scoring tool was based on 4 domains of change: inflammatory, vascular, muscle fiber, and connective tissue. Using a Latin square design, biopsy samples were scored by 11 experts for items in each domain, and for a global abnormality measure using a 10-cm visual analog score (VAS 0-10). The tool's reliability was assessed using an intraclass correlation coefficient (ICC) and scorer agreement (alpha) by determining variation in scorers' ratings.

RESULTS

There was good agreement in many items of the tool, and several items refined between the meetings improved in reliability and/or agreement. The inflammatory and muscle fiber domains had the highest reliability and agreement. The overall VAS score for abnormality had high agreement and reliability, reaching an ICC of 0.863 at the second consensus meeting.

CONCLUSION

We propose a provisional scoring system to measure abnormalities on muscle biopsy samples obtained from children with juvenile DM. This system needs to be validated, and then could be used in prospective studies to test which features of muscle pathology are prognostic of disease course or outcome. We suggest that the process we used could be a template for developing similar systems in other forms of myositis.

DNA sequence of the translocation breakpoints in undifferentiated embryonal sarcoma arising in mesenchymal hamartoma of the liver harboring the t(11;19)(q11;q13.4) translocation

Undifferentiated embryonal sarcoma of the liver is a highly malignant and aggressive tumor that occasionally arises within mesenchymal hamartoma of the liver (MHL), a benign tumor that typically occurs in young children. Undifferentiated embryonal sarcoma arising in MHL, as well as uncomplicated MHL, frequently harbor rearrangements of band 19q13.4, including the translocation t(11;19)(q13;q13.4). In this study we report the cloning and DNA sequence analysis of the translocation breakpoints in an undifferentiated embryonal sarcoma arising in MHL known to harbor t(11;19). In this case, the breakpoint at 11q13 occurred in the MALAT1 gene, also known as ALPHA. MALAT1 is rearranged in renal tumors harboring the t(6;11)(p21;q13) translocation, and noncoding MALAT1 transcripts are overexpressed in a number of human carcinomas. The breakpoint at 19q13.4 occurs at a locus we refer to as MHLB1, for Mesenchymal Hamartoma of the Liver Breakpoint 1. Although the MHLB1 locus does not contain a known gene, several human ESTs map to the region (a subset of which show homology to the nuclear RNA export factor (NXF) gene family), and the region is conserved between many mammalian species.

Mutations in the MPV17 gene are responsible for rapidly progressive liver failure in infancy

MPV17 is a mitochondrial inner membrane protein of unknown function recently recognized as responsible for a mitochondrial DNA depletion syndrome. The aim of this study is to delineate the specific clinical, pathological, biochemical, and molecular features associated with mitochondrial DNA depletion due to MPV17 gene mutations. We report 4 cases from 3 ethnically diverse families with MPV17 mutations. Importantly, 2 of these cases presented with isolated liver failure during infancy without notable neurologic dysfunction.

CONCLUSION

We therefore propose that mutations in the MPV17 gene be considered in the course of evaluating the molecular etiology for isolated, rapidly progressive infantile hepatic failure.

MLC1 is associated with the dystrophin-glycoprotein complex at astrocytic endfeet

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a progressive cerebral white matter disease with onset in childhood, caused by mutations in the MLC1 gene. MLC1 is a protein with unknown function that is mainly expressed in the brain in astrocytic endfeet at the blood–brain and cerebrospinal fluid–brain barriers. It shares its localization at astrocytic endfeet with the dystrophin-associated glycoprotein complex (DGC). The objective of the present study was to investigate the possible association of MLC1 with the DGC. To test this hypothesis, (co)-localization of DGC-proteins and MLC1 was analyzed by immunohistochemical stainings in gliotic brain tissue from a patient with multiple sclerosis, in glioblastoma tissue and in brain tissue from an MLC patient. In control tissue, a direct protein interaction was tested by immunoprecipitation. Results revealed that MLC1 is co-localized with DGC-proteins in gliotic brain tissue. We demonstrated that both MLC1 and aquaporin-4, a member of the DGC, were redistributed in glioblastoma cells. In MLC brain tissue, we showed absence of MLC1 and altered expression of several DGC-proteins. We demonstrated a direct protein interaction between MLC1 and Kir4.1. From these results we conclude that MLC1 is associated with the DGC at astrocytic endfeet.

Inborn errors of bile acid metabolism

Bile acids are synthesized by the liver from cholesterol through a complex series of reactions involving at least 14 enzymatic steps. A failure to perform any of these reactions will block bile acid production with failure to produce "normal bile acids" and, instead, result in the accumulation of unusual bile acids and intermediary metabolites. Failure to synthesize bile acids leads to reduced bile flow and decreased intraluminal solubilization of fat and fat-soluble vitamins. In some circumstances, the intermediates created because of blockade in the bile acid biosynthetic pathway may be toxic to hepatocytes. Nine recognized inborn errors of bile acid metabolism have been identified that lead to enzyme deficiencies and impaired bile acid synthesis in infants, children, and adults. Patients may present with neonatal cholestasis, neurologic disease, or fat and fat-soluble vitamin malabsorption. If untreated, progressive liver disease may develop or reduced intestinal bile acid concentrations may lead to serious morbidity or mortality. This review focuses on a description of the disorders of bile acid synthesis that are directly related to single defects in the metabolic pathway, their proposed pathogenesis, treatment, and prognosis.

Combined omphalomesenteric and urachal remnants in an 18-month-old girl

A toddler with a persistent congenital umbilical papule is described. The papule was found to contain both omphalomesenteric and urachal remnants. This patient's findings illustrate the importance of further evaluation of umbilical lesions when conventional therapy with silver nitrate fails.

Predictability of the clinical course of juvenile dermatomyositis based on initial muscle biopsy: A retrospective study of 72 patients

OBJECTIVE

Except when the diagnosis of juvenile dermatomyositis (DM) is in doubt, a case has not been made for routine muscle biopsy (MB). We sought to determine whether MB findings prior to systemic therapy have prognostic value.

METHODS

We reviewed the hospital records and slides prepared from the initial open MB of 72 patients treated at one center between 1977 and 2002 and followed for a minimum of 2 years. None of the patients had received a course of systemic corticosteroid therapy at the time of MB. Our approach to MB evaluation was based on recent discussions with muscle pathology experts to develop criteria for assessing inflammation, vasculopathy, myofiber atrophy, regeneration, acute and chronic myopathic change, and stromal changes. Using simple and multivariate logistic regression, we tested each MB parameter for ability to predict outcome using 2 published classification systems.

RESULTS

Extensive active myopathic changes (excluding regeneration) and central nuclei without basophilia predicted chronic juvenile DM. Severe arteropathic change, positive arterial direct immunofluorescence, obvious foci of severe capillary loss/endomysial fibrosis, and muscle infarcts predicted chronic juvenile DM, particularly with ulceration. Other MB parameters, regardless of severity, were not significant predictors of chronic juvenile DM versus limited disease.

CONCLUSION

A scoring system for evaluating pretreatment MB in juvenile DM that focuses on extent of necrotizing myopathy, severity of vasculopathy, and features of established chronicity such as central nucleation of nonbasophilic myofibers may provide a basis for stratification of therapeutic regimens according to risk for chronic disease. The validity of our findings should be prospectively tested.

Proliferative activity of human thyroid cells in various age groups and its correlation with the risk of thyroid cancer after radiation exposure

CONTEXT

The thyroid gland is vulnerable to the carcinogenic effects of ionizing radiation, and there is a well-documented inverse correlation between thyroid cancer and age at exposure, particularly for ages less than 20 yr. One of the factors responsible for this phenomenon may be more rapid cell proliferation in children.

OBJECTIVE

The objective of this study was to determine the proliferative rate of normal human thyroid cells in different age groups.

DESIGN

We used immunohistochemical analysis to determine the Ki-67 proliferative index in 117 thyroid glands obtained at autopsy, including 25 fetal thyroids (11-40 wk gestation), 55 childhood thyroids (0-19 yr), and 37 adult thyroids (20-60 yr).

RESULTS

The rate of Ki-67 labeling in the three groups was 7.4 +/- 6.10, 0.23 +/- 0.15, and 0.08 +/- 0.04% respectively, demonstrating an overall trend for diminishing proliferative activity of thyroid cells with increasing age. However, a lack of correlation was noted between the slopes of cancer risk calculated from previous studies of irradiated populations and proliferative rate in the pediatric age intervals of 0-4 and 5-9 yr, suggesting that other factors are likely to be responsible for the particularly high sensitivity to radiation-induced thyroid cancer among the youngest children.

CONCLUSIONS

Our findings of a general decrease in proliferative activity of thyroid cells with age may explain, at least in part, the higher risks of radiation-related thyroid cancer in children compared with adults. However, the variation in the rate of cell proliferation is unlikely to be responsible entirely for this phenomenon and other factors may also be involved.

What more can we learn from muscle histopathology in children with dermatomyositis/polymyositis?

OBJECTIVE

To correlate disease course and complications in children with juvenile dermatomyositis (JDM) and polymyositis (JPM) with specific features of muscle pathology on biopsy.

METHODS

This is a retrospective cohort analysis of 59 children diagnosed with JDM or JPM between 1965 and 1998 and followed at the Cincinnati Children's Hospital Medical Center (CCHMC) for a mean duration of 7.3 years (range 1.1-24.5 years). Disease course was characterized as limited, chronic non-ulcerative or chronic ulcerative, similar to previously defined disease course subtypes reported by Crowe et al.(1). All subjects had diagnostic muscle biopsies performed at CCHMC and had disease for at least two years' duration in order to classify their disease course as either limited or chronic. Features of muscle histopathology that were evaluated included loss of the intramuscular capillary bed, infarct, perifascicular myopathy, direct immunofluorescence (DIF) staining of the intramuscular vasculature and specifically, the locale of DIF staining, i.e., small arteries or capillaries. Disease complications that were assessed included calcinosis, contractures, muscle atrophy, lipodystrophy, gastrointestinal ulceration, cutaneous ulceration and death. Data analysis was completed using Chi-square or Fisher's exact tests and logistic regression modeling.

RESULTS

Twenty-two children (37%) had limited disease, 24 (41%) had chronic non-ulcerative disease and 13 (22%) had chronic ulcerative disease. Neither loss of the intramuscular capillary bed nor perifascicular myopathy on muscle biopsy significantly correlated with disease course or the various complications evaluated in this study. DIF staining of intramuscular vessels overall was not significantly associated with clinical disease course, but the localization of DIF staining to intramuscular arteries (rather than to capillaries) was significantly associated with the outcome of chronic ulcerative disease. Nine of the 13 children with chronic ulcerative disease had DIF-arterial staining on muscle biopsy (69%), significantly greater than DIF-arterial staining in children with limited disease (32% had DIF-arterial staining) (p = 0.04), chronic non-ulcerative disease (8% had DIF-arterial staining) (p = 0.0002), and non-ulcerative disease overall (limited + chronic non-ulcerative disease groups combined) (20% had DIF-arterial staining), with p = 0.001. Additionally, lack of DIF-arterial staining on biopsy was significantly correlated with patients not having gastrointestinal ulceration (p = 0.002), cutaneous ulceration (p = 0.004) and/or death (p = 0.02) as disease-related complications. Infarct on muscle biopsy was significantly associated with the development of chronic ulcerative disease (p = 0.02), being present on biopsy in 23% of children with chronic ulcerative disease compared with none of the patients with chronic non-ulcerative disease and 4% of those with limited disease. Infarct on muscle biopsy correlated with the outcomes of death (p = 0.01) and gastrointestinal ulceration (p = 0.03), but not with the development of cutaneous ulceration (p = 0.18).

CONCLUSION

DIF-arterial staining and infarct on muscle biopsy are significantly associated with the development of chronic ulcerative disease in JDM and JPM, while perifascicular myopathy and loss of the intramuscular capillary network are not associated with disease course. The presence of DIF-arterial staining and infarct on biopsy should suggest early use of second-line therapeutic agents to more quickly bring disease activity under control.