Hypothyroidism with ATP8B1 Deficiency

A recent study (L Li et al. J Pediatr 2015; 157: 1334-9) indicated that hypothyroidism may be another extrahepatic feature of patients with ATP8B1 deficiency; this mutation’s main manifestation has been intrahepatic cholestasis in either progressive familial intrahepatic cholestasis (PFIC type 1) or benign recurrent intrahepatic cholestasis (BRIC type 1).

In this study, 3/13 were hypothyroid and an additional 2/13 had subclinical hypothyroidism.  These patients were compared with a cohort of children with ABCB11 deficiency (PFIC type 2 or BRIC type 2) in which 0/19 had hypothyroidism.

Related blog posts:

Targeted Therapy for PFIC type 2

Progressive Familial Intrahepatic Cholestasis, type 2, (PFIC2) is due to decrease (or absent) function of the bile salt export pump (BSEP) encoded by ABCB11 has been treated mainly in a symptomatic manner with medicines like ursodeoxycholic acid and sometimes biliary diversion.  PFIC2 has been associated with increased risk for hepatocellular carcinoma (HCC).

A recent study (E Gonzales, et al. Hepatology 2015; 62: 558-66) indicates that newer therapies targeting the specific mutation may be effective.

In this study, treatment with oral 4-phenylbutyrate (4-PB) in four patients improved pruritus, serum bile acid concentrations, and liver function tests. 4-PB is considered a chaperone drug and may partially correct mistrafficking.

The associated editorial (pg 349-50) notes that 4-PB has an unpleasant taste and requires ingestion of a large number of pills. In addition, patients with complete loss of BSEP, 4-PB will not be effective. Finally, even in patients with a clinical response, it is unclear if this will lower the risk of HCC.

A second study (S Varma et al. Hepatology 2015; 62: 198-206) retrospectively studied 22 children with PFIC2.  “Children with late-onset presentation, lower ALT, and intracellular BSEP expression are likely to respond, at least transiently, to nontransplant treatment.”  Nontransplant treatment in this cohort included ursodeoxycholic acid in 19 (10 mg/kg thrice daily) and partial biliary diversion in 3.  Higher ALT values were considered to be >165 IU/L. Another point in this study: response to treatment can be slow and take many months.

My take: These studies provide useful information about which patients with PFIC2 respond medically and introduce a new therapy, 4-PB.

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Is this really newsworthy? Perhaps next week: man with venomous snakes says they make great pets?

Perhaps next week the story will be: man with venomous snakes says they make great pets?

Clinical Features of Byler Disease

A recent article (Morris AL, et al. JPGN 2015; 60: 460-6) provides a detailed analysis of six cases of Byler disease during their first two years of life.  These cases were strictly defined and defined by homozygous c.923G>T mutation of ATP8b1.

Presenting features:

  • 2 with newborn direct hyperbilirubinemia
  • 2 with complications of coagulopathy. “Bleeding diathesis is a particular issue in the Amish community where home delivery is common and vitamin K may not be administered perinatally.”
  • 1 with failure to thrive and rickets
  • 1 was a sibling identified with newborn genetic testing

Key features:

  • Intensive fat-soluble vitamin supplementation was needed. “Vitamin K deficiency can be lethal.”
  • Poor growth was frequent (Figure 2): “growth trajectories were generally at the low end of percentiles and did not reflect parental size.” It was “typically responsive to supplementation with medium-chain triglyceride-based formula. and/or use of 30 cal per ounce formulae.”
  • Elevated serum bile acids and low normal GGT (Υ-glutamyltranspeptidase)
  • Diarrhea was commonly reported
  • Intractable pruritus in 4 of 6 children which developed between 6-12 months of age;  in two patients rifampin therapy was effective.
  • Partial external biliary diversion was used in 4 children during 2nd year of life; there was a “generally favorable response to PEBD.”
  • There were not issues noted with portal hypertension

Bottomline: This report shares some practical experience with this rare disorder.

Related blog posts:

“Genetic Testing and the Future of Pediatric Gastroenterology”

Last night, a symposium on “Genetic Testing and the Future of Pediatric Gastroenterology” sponsored by Children’s Healthcare of Atlanta took place.  The speakers included Dr. Ben Gold from our pediatric GI group (GI Care for Kids), Dr. Saul Karpen and Dr. Subra Kugasthasan (Emory), and Dr. Robert Heuckeroth (CHOP).

This blog entry has abbreviated/summarized the presentations. Though not intentional, some important material is likely to have been omitted; in addition, transcription errors are possible as well.  All of the speakers had terrific presentations.

GI Genetic Testing –Subra Kugathasan

Reasons for genetic testing:

  • Predicting prognosis: predicting stricturing/fibrosis in Crohn’s, predicting cancer in ulcerative colitis; BRCA1 in breast cancer
  • Choosing the right medicine: pharmcogenomics
  • Precision medicine: prevention of disease, slowing progression of disease.

Examples in current medicine:

  • Recurrent pancreatitis –novel mutations identified in SPINK1.  Also now hereditary pancreatitis may be due to mutations in CPA1, GGT1, CLDN2, MMP1, MTHFR in addition to CTRC, SPINK1, CFTR, and PRSS1.
  • Inflammatory bowel disease (IBD):IL10 Receptor mutation , TTC7A –>VEO IBD; IPEX gene (can worsen with immunosuppression). Panel testing now available for 40 genes –4 of 22 patients identified with IBD.  Identifying cause of VEO IBD may lead to treatment: bone marrow transplantation.
  • IBD: CLIA/CAP certified Emory Genetics panel ~50 genes (genetics.emory.edu/egl/tests/view.php?testid=4420). Dr. Kugathasan indicated that this testing is likely to be a better 1st step then exome testing. Yield with exome sequencing (in highly selected populations) about 25% at this time but likely to increase. If negative, can proceed with whole exome sequence.  Numerous problems with exome sequencing; for example, exome sequencing may identify genes of unknown significance and identifying genetic problems unrelated to clinical issue.

Who/When to test?

  • Very early onset disease (<10 years), atypical presentation, perhaps treatment-refractory.

Take-home point: “All GI diseases have genetic testing in future.” Testing for highly selected patients for gene defects can be accomplished with gene panel and if negative, whole exome testing.

Related blog posts:

Liver: Cholestatic & Metabolic Diseases of Infants and Children —Saul Karpen

Potential areas for genetic testing:

  • Neonatal cholestasis: PFIC, Metaboic, Biliary Atresia
  • NAFLD
  • Transplant

“Why bother…they all get transplanted anyway…”  According to Dr. Karpen, this view needs to be reconsidered.

Neonatal cholestasis:

  • (Front Pediatr 2014; 2: 65)  41% with biliary atresia, 13% idiopathic, and a lot of others.  N=82. Other etiologies: Genetic disorders; Biliary disease (eg. Caroli), transporter defects (PFICs/BRICs), Metabolic (Niemann-Pick C, tyrosinemia, HFI, Peroxisomal, GSDs, Peroxisomal, Mitochondrial, A1AT). Thus, panels to identify these disorders can be very helpful.
  • Emory Cholestasis 56+ Gene Panel. Testing is cheaper than endoscopy

PFIC: Progressive Familial Intrahepatic Cholestasis

  • PFIC1: ATP8B1 (Byler) –besides cholestasis, patients often with diarrhea, hearing loss, very itchy; can have cirrhosis at 2 years of life
  • PFIC2: ABCB11 (BSEP deficiency) –can have cirrhosis at 6 mo, prone to HCC (as early as 13 mo), very itchy
  •  PFIC3 (high GGT) ABCB4 –can have cirrhosis at 5 mo, can cause problems at later ages as well (eg. intrahepatic cholestasis of pregnancy, gallstones); increase risk for HCC/cholangiocarcinoma.
  • Identifying PFIC (could mimic PSC) and BRIC (Benign Recurrent Intrahepatic Cholestasis)–is helpful in following patients for specific management when symptoms recur and to screen for complications (eg. HCC).

Biliary Atresia:

  • No clear genetics in most
  • Laterality defects in 5-10% -asplenia/polysplenia, cardiac defects
  • GPC1 gene is a susceptibility gene in zebrafish
  • ADD3 gene identified in Han Chinese OR 2.38 –may be a susceptibility gene. (30% of cases, 17% of controls)

NAFLD: Associated with increased mortality compared with matched controls. Patients develop thicker atherosclerotic plaques. PNPLA3 gene identified as a susceptibility gene for NAFLD and is highly prevalent in Hispanic populations.  Similarly, PNPLA3 has been associated with NASH in Italian populations.  If you have this genotype, this increases risk of liver fat in the face of increased sugar consumption.

Transplant medicine: Deoxyguanosine Kinase Deficiency (DGUOK) –rapid sequencing for this gene pretransplant –If positive, should not be transplanted. These individuals have systemic disease that cannot be cured with liver transplantation.

Who/When for genetic testing?: DGUOK in liver failure patients, and in infants without diagnosis after liver biopsy/exclusion of A1AT

Take-home message: Genetic testing has a role in pediatric liver disease and it is affordable.

Related blog posts:

GI –Single Microbes to the Microbiome and GI Disease —Ben Gold

  • Described why changes in our environment can trigger development of disease due to changes in microbiome (eg. immigrants/children with IBD in developed countries at much higher rate than at developing countries)
  • Discussed Helicobacter pylori –‘how a single microbe which may have been good turned bad’
  • Described pathogenesis. What you get exposed to early on may lead to an exaggerated response by T-cells/immune system.  Healthy microbiota is critical to train the immune system via GALT to protect host and decrease the chances for immune overexpression.

Key points:

  • 100 trillion bacteria that live in our GI tract. 10x number of human cells in our body and 100x as many genes as there are in the human genome.  Partnership between humans and their microbiome developed over thousands of years.
  • Vaginal delivery is NOT sterile. Are there consequences to C-section? Food allergy for infant –OR 2.5 if Mom with food allergy delivers vaginally vs OR 7.8 if Mom has food allergy and delivers via C-section. Also, some data indicates increased risk of EoE if born via C-section.  From DAY 1, microbiome can be influence by environmental factors.
  • Influencing microbiome happens mainly during first three years of life.

Why the microbiome is so important/more pointers:

  1. Since 1950, there has been a huge decline in infectious diseases like measles, mumps, hepatitis A, tuberculosis, etc
  2. Coincident with these decreases there has been increased multiple sclerosis, Crohn’s disease, asthma, food allergy, autoimmune diseases
  3. Sanitized food supply, decrease in naturally fermented foods, urban lifestyle, antibiotics, C-section all lead to lower microbial exposure and altered intestinal microbiota. This in turn may lead to an inadequate immune response.
  4. Elie Metchnikoff 1845-1916: suggested ingested bacteria could be healthy. Probiotics/prebiotics are not a new idea!
  5. Obese patients had very high levels of Firmicutes and low Bacteroidetes.
  6. Fecal microbial transplantation (FMT)–reseeding GI microbiome. FMT may be beneficial to many diseases and is being  studied.

Helicobacter pylori -evidence of H pylori as far back as 60,000 years ago and has evolved with humans. H pylori may have helped provided a positive immune response in children and adults.

Bottomline: Human genetic diseases may be heavily influenced by the 300 trillion bacteria and their genes; these bacteria are susceptible to environmental disease.

Related blog posts:

 

Genetic Basis of Motility —Robert Heuckeroth

  • Basic machinery controlling motility described –enteric neurons, muscles, pacemaker cells.
  • Very little clinical overlap between modern genetic testing and applicable motility disorders: achalasia, gastroparesis, pseudoobstruction, Hirschsprung’s or irritable bowel
  • Focused testing for suspected diagnosis is being displaced by broader testing in serious disease, especially since more extensive genetic testing may be more cost-effective. When to do exome sequencing?

Hirschsprung’s disease:

  • 1:5000 children.
  • 100X higher risk in Down Syndrome.
  • Prenatal testing not helpful at this time. There may be >360 genes that increase risk (variable degree of risk) of Hirschsprung’s disease; hence prenatal testing not that helpful at this time.
  • 30 associated genetic syndromes with Hirschsprung’s, >12 known gene defects.  Hirschsprung’s disease: 25% with RET haploinsufficiency.  RET haploinsufficiency –increases risk of Hirschsprung’s disease >2500-fold risk.
  • Gene environment interactions can increase risk of developing Hirschsprung’s disease –if vitamin A deficient, mice with increased risk.
  • RET gene –>too little RET increases risk of Hirschsprung’s
  • RET gene –>too much RET increases risk of MEN2B, MEN2A.  Though 7.5% of MEN2A have Hirschsprung’s –works out to be 1 in 100 kids with Hirschsprung’s have MEN2A mutations.  ??test for this??

Pseudoobstruction genetic basis– a number of genes identified, including ACTG2 (smooth muscle actin gene).  If you understand etiology, this may lead to prevention and treatment.

Take-home message: Currently biggest problem with genetic testing, especially with motility disorders, is identifying genetic defect of unknown significance.  Thus, testing needs to be done as part of research studies.

Related blog posts:

 

 

 

Understanding Cholestatic Pruritus

A recent review (Hepatology 2014; 60: 399-407) sorts out “facts and fiction” with regard to pruritus in cholestasis.

The authors note that for more than 2000 years there has been a search for the potential pruritogen in cholestasis, “when Aretaeus the Cappadocian (2nd century B.C.) stated that ‘pruritus in jaundiced patients is caused by prickly bilious particles.'”

Key points of review:

Pruritus affects a large number of hepatobiliary diseases

  • Hepatocellular cholestasis: intrahepatic cholestasis of pregnancy (ICP), benign recurrent intrahepatic cholestasis (BRIC), progressive familial intrahepatic cholestasis (PFIC1, PFIC2), Hepatitis C
  • Biliary-liver diseases: primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC), PFIC3, Alagille, Drug-induced diseases
  • Obstructive cholestasis: gallstones, IgG4-associated cholangitis, biliary atresia, and other causes

Most recently lysophosphatidic acid LPA) and autotaxin (ATX) have been shown to be important pruritogen candidates in cholestasis

  • “ATX is the main source of circulating LPA levels…In cholestasis, serum ATX activity, but not other putative markers of itch such as serum bile salt levels or serum μ-opiod activity, were correlated with itch intensity.”
  • “Rifampicin was found to reduce ATX expression at the transcriptional level.”  This may explain rifampicin’s efficacy for pruritus in cholestasis.
  • “When the enterohepatic circulation is interrupted by nasobiliary drainage, circulating levels of ATX rapidly dropped concomitant with relief of pruritus.”  So, while ATX is not secreted into bile, other substances in bile, like steroid hormones, like play a role in the induction of ATX.

Current therapeutic recommendations (dosing recommendations provided by authors in Table 3)

  • 1st line: Cholestyramine (except in ICP in which ursodeoxycholic acid is considered 1st line)
  • 2nd line: Rifampicin
  • 3rd line: naltrexone
  • 4th line: sertraline
  • Experimental: ondansetron, phenobarbitol, propranolol, lidocaine, dronabinol, butorphanol, phototherapy, nasobiliary drainage, plasmapharesis (and similar treatments), biliary diversion
  • Liver transplantation

Related blog posts:

Disclaimer: These blog posts are for educational purposes only. Specific dosing of medications/diets (along with potential adverse effects) should be confirmed by prescribing physician/nutritionist.  This content is not a substitute for medical advice, diagnosis or treatment provided by a qualified healthcare provider. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a condition.

Emerging Treatment for PFIC-2

A great example of “bench to bedside” research was recently published (J Pediatr 2014; 164: 1219-27). While this research involved treatment of a rare condition, progressive familial intrahepatic cholestasis type 2 (PFIC2), the way the authors used a series of convincing experiments to determine the effect of a new medication shows how important a single patient can be in advancing medical treatment.  For PFIC2, the implications of this study are more direct since there are no established medications.

Previous experimental evidence has indicated that 4-phenylbutyrate (4PB), a drug used to treat ornithine transcarbamylase deficiency (OTCD), can increase the expression of the bile salt export pump (BSEP). Since BSEP, encoded by ABCB11 gene, is defective in PFIC2, the authors sought to determine whether 4PB would be effective for patients with PFIC2 who showed a reduced (but not absent) BSEP expression.

They identified a jaundiced infant female at 2 months of age with normal GGT who was diagnosed with PFIC2 due to the presence of the c.3692G>A (p.R1231Q) mutation in both alleles of ABCB11.

The authors then treated this infant with 200 mg/kg/day (into 4 doses a day) with 4PB; gradually the dosage was increased to 500 mg/kg/day.  The authors performed elegant in vitro studies from genomic DNA from peripheral leukocytes along with histologic studies from liver biopsy specimens.

Key Findings:

At the 500 mg/kg/day dosage, BSEP expression at the canalicular membrane was partially restored and this coincided with improved liver tests, improved liver histology, and relief of pruritus.

Conclusion: 4PB retards degradation of the canalicular BSEP which resulted in biochemical and histologic improvement.  This study involved only one patient; thus, further studies will be needed.

Related blog post:

BRIC, PFIC, and nasobiliary drainage | gutsandgrowth

BRIC, PFIC, and nasobiliary drainage

Case reports, when effective, help clinicians understand meaningful differences in disease presentation; in addition, they highlight practical treatment approaches.  An excellent example of one such case report is the following:

  • Zellos A et al.  JPGN 2012; 55: 88-90

These authors present a case with unique features that highlight some of the clinical problems with benign recurrent intrahepatic cholestasis (BRIC) and progressive familial intrahepatic cholestasis (PFIC).  BRIC1 and PFIC1 are associated with mutations in ATP8B1; BRIC2 and PFIC2 are associated with mutations in ABCB11.  The primary difference between BRIC and PFIC is the phenotypic expression.  In BRIC, individuals have episodes of cholestasis; in PFIC, progressive chronic liver disease develops in the first months of life.  PFIC2/ABCB11 mutations cause defective bile salt export pump (BSEP) at the bile-canniculus membrane.

Both ATP8B1 and ABCB11 intrahepatic cholestasis conditions present in a similar fashion with low GGT values.  In this case report, a 5-year-old presented with jaundice, acholic stools and dark urine.  His laboratory values revealed an ALT of 60 U/L, direct bilirubin of 7.6 mg/dL and gamma-glutamyl transpeptidase (GGT) of 10 U/L.  Initially, after exclusion of other liver conditions (eg. NL MRCP, copper studies, α-1 antitrypsin, autoimmune serology, infectious etiologies), the authors suspected ‘a clinicopathologic intergrade between BRIC and PFIC’ likely due to ATP8B1 as there was BSEP expression on liver biopsy immunostaining.  After sequencing did not demonstrate any ATP8B1 mutations, the authors identified two heterozygote mutations in ABCB11.

From a treatment standpoint, once nasobiliary drainage (NBD) was in place, the patient quickly improved.  This occurred after >6 weeks of failure with urosdeoxycholic acid/conservative measures.  As a precaution, the authors cultured the bile once a week and instituted antibiotic treatment when positive cultures were identified.

One other point alluded to by the authors is that the natural history of BRIC2 is poorly described.  Whether this disorder is truly ‘benign’ as the name suggests is unclear.  In patients with similar mutations who develop PFIC2, there is a high risk of hepatocellular carcinoma (HCC).

Intrahepatic Cholestasis Genes/Disorder (Clin Liver Dis 2006; 10: 27-53.)

Gene: Disorder (protein)
ABCB11: PFIC 2, BRIC 2 (BSEP)
ABCB4: PFIC 3, ICP (MDR3)
CFTR: CF (CFTR)
ATP8B1: PFIC1 -Byler’s (FIC1), BRIC, GFC -Greenland Familial
CLDN1: NISCH (Claudin 1) -neonatal sclerosing cholangitis/icthyosis
VPS33B: ARC syndrome (Vascular protein sorting 33) -arthrogryposis-renal dysfn-cholestasis, low GGT
AKR1D1: BAS: Bile acid synthetic defect: neonatal cholestasis with giant cell hepatitis
(5β-reductase)
HSD3B7: BAS (C27-3β-HSD)
CYP7BI: BAS (CYP7BI)
TJP2: (ZO-2) FHC: Familial hypercholanemia (tight junction protein)
BAAT: FHC (BAAT)
EPHX1: FHC (epoxide hydrolase)
JAG1: Alagille (JAG1) JAG1 is transmembrane cell-surface protein important in regulating cell fate during embryogenesis
PKHD1: ARPKD (fibrocystin -important in ciliary function and tubulogenesis)
PRKCSH: ADPLD (hepatocystin)
ABCC2: Dubin-Johnson syndrome (MRP2)
CIRH1A: NAIC -N Amer Indian childhood cirrhosis (Cirhin)

Additional references for BRIC/low GGT PFIC:

  • -JPGN 2010; 51: 494.  Use of biliary diversion –helpful in 18 PFIC2 cases with long-term f/u.
  • -Liver Transplantation 2010; 16: 856.  6 patients developed recurrent low gamma-glutamyl transpeptidase cholestasis, that mimics BSEP disease, following transplantation. All had documented genetic defects in ABCB11 that were predicted to lead to a congenital absence of BSEP protein.
  • -NEJM 2009; 361: 1359. Recurrence of BSEP deficiency p OLT due to antibodies against BSEP
  • -Hepatology 2010; 51: 1645. n=62 children & clinical course.
  • -Gastroenterol 2008; 134: 1203. Severe BSEP –82 different mutations in 109 families. (n=132 patients)
  • -JPGN 2008; 46: 241. Excellent review. FIC1 caused by mutations in ATP8B1, PFIC 2 caused by mutations in ABCB11 which encodes BSEP – bile salt export pump. Increased risk of HCC in PFIC2 especially.
  • -J Pediatr 2007; 150: 556.  Increase risk of HCC in PFIC2.
  • -Hepatology 2006; 44: 478-486. Cases of pediatric HCC in PFIC-2
  • -Gastroenterol 2006; 130: 908. Review of canalicular transport defects.
  • -Hepatology 2005; 42: 222. summary of cholestasis workshop
  • -Gastroenterol 2004; 126: 322. Review of bile salt transporters.
  • -JPGN 2002; 34: 7A. FTT, diarrhea persist p biliary diversion or transplant.

PFIC3 -High GGT

  • -Gastroenterol 2003; 124: 1037-42. MDR3 mutations causing cholelithiasis, cholestasis, biliary cirrhosis, & pregnancy cholestasis.
  • -Gastroenterol 2001; 120: 1448-1458. n=31 cases. MDR3 mutations. ABCB4 gene
  • -Gastroenterol 2001; 120: 1459-67. Gallbladder stones & chronic cholestasis in 6 MDR3+ pts. Avg age of presentation: 2.9yrs. Avg age of Tx: 7.5yrs.  Sx/S : high ggt cholestasis, pruritus, intrahepatic cholestasis of pregnancy in heterozygotes (& c contraception)
  • -Hepatology 1996; 23: 904-8. MDR3 gene assoc c PFIC