Insight Into Alpha-1 Antitrypsin Heterozygosity

CV Schneider, K Hamesch et al. Gastroenterol 2020; 159: 534-548Liver Phenotypes of European Adults Heterozygous or Homozygous for Pi∗Z Variant of AAT (Pi∗MZ vs Pi∗ZZ genotype) and Noncarriers)

Key findings:

  • Ten percent of subjects with the Pi∗MZ genotype vs 4% of noncarriers had LSMs (liver stiffness measurements) of 7.1 kPa or more (adjusted odds ratio, 4.8; 95% confidence interval, 2.0–11.8)
  • Obesity and diabetes were the most important factors associated with LSMs ≥7.1 kPa in subjects with the Pi∗MZ genotype.
  • AAT inclusions were detected in liver biopsies of 63% of subjects with the Pi∗MZ genotype, vs 97% of subjects with the Pi∗ZZ genotype, and increased with liver fibrosis stages.

The associated editorial (pg 433-34) noted that Pi∗MZ genotype is a disease modifier in cystic fibrosis, alcoholic liver disease, and nonalcoholic liver disease.

My take: This study indicates that Pi∗MZ genotype for alpha-one antitrypsin are more likely to develop liver fibrosis in the presence of other risk factors like obesity and diabetes mellitus.

Related blog posts:

Alpha-1-Antitrypsin Deficiency

A recent terrific review on Alpha-1-Antitrypsin (A1AT) Deficiency: P Strnad et al. NEJM 2020; 382: 1443-55

Background:

  • 95% of A1AT deficiency is due to homozygosity for the Z allele; prevalence of 1 in 2000 in those of European descent.
  • A1AT protects the lung tissue against attack by the enzyme neutrophil elastase.
  • The presence of A1AT genetic variants suggests that these mutations may confer a selective advantage, perhaps by amplifying the inflammatory response to invasive respiratory/gastrointestinal infections.

Pathophysiology/Clinical Features:

  • Table 1 lists the key alleles/mutations associated with A1AT deficiency -17 deficiency/null listed including: F, I, Iners, King’s, M-malton, M-procida, Pittsburgh, Queen’s, S, S-iyama, Z, QO-bellingham, QO-granitefalls, QO-hongkong
  • S allele deficiency often results in disease (emphysema, cirrhosis) in the setting of SZ heterozygotes.  The disease is typically less severe than in ZZ disease.  This allele is the most common deficiency variant (1 in 5 in Southern Europe, 1 in 30 in U.S.)
  • Z allele deficiency is the most common severe deficiency variant.  Carrier frequency: 1 in 27 persons in Northern Europe, 1 in 83 in the U.S. It is NOT seen in China, Japan, Korea, Malaysia, or Northern and Western Africa.

PI ZZ Genotype:

  • 73% of infants with PI ZZ genotype had elevated ALT level in the 1st 12 months of life
  • Cholestatic jaundice noted in 10% of infant; 15% of these infants progress to juvenile cirrhosis
  • Only 15% with abnormal ALT values by 12 years of age
  • 35% of adults with ZZ genotype show clinically-significant liver fibrosis. Risk factors for advanced fibrosis: male gender, metabolic syndrome/obesity, and alcohol consumption.

Lung Disease Due to A1AT Deficiency:

  • The clinical features of lung disease due to A1AT deficiency are “mainly indistinguishable from those of nonhereditary emphysema…this is partly why severe A1AT deficiency remains undiagnosed in approximately 90% of case, with an interval of 5 to 7 years from the onset of symptoms to diagnosis.”  When the diagnosis is late, lung disease has become irreversible.
  • Early diagnosis allows lifestyle changes (eg. smoking cessation), reduction in occupational risks, and access to therapies.

MZ Phenotype:

PI MZ genotype is more susceptible to multiple disorders, including a predisposition to COPD (at least among smokers) with odds ratio of 1.4.  Other conditions with increased risk: NAFLD-related cirrhosis (OR 3-7), Alcoholic cirrhosis, and CF-associated liver disease

Treatment:

  • Smoking cessation
  • Plasma-purified A1AT infusions.  “Randomized, controlled trials have focused on decreased loss of lung density as the primary efficacy outcome;” however, augmentation therapy has not been to shown to effect other measures, “such as FEV1, quality of life, or exacerbation of COPD.”

Related blog posts:

Also, this study was previously alluded to by this blog, but now is in print:

Briefly noted: X Lu et al. SARS-CoV-2 Infection in Children (NEJM 2020; 382: 1663-5). In 171 Chinese children with confirmed SARS-CoV-2 infection, 41.5% had fever during illness; 27 (15.8%) had no symptoms of infection or radiographic findings. Three required ICU/ventilator support; all had coexisting conditions.  One 10 month old child with intussusception died.

Liver Shorts March 2020 & COVID-19 Screenshots

Sofusbuvir and Ribavirin for children with hepatitis C infection (3-12 yrs, genotype 2 or 3) P Rosenthal et al. Hepatology 2020; 71: 31-43. n=54.  SVR12 was 98% (one patient did not complete treatment).

Alpha-one antitrypsin heterozygositiy contributes to cirrhosis in fatty liver disease. Liver Transplantation 2020; 26: 17-24. From the discussion: “unexpected PASD+ globules, in the context of advanced liver disease, are a specific finding that indicates the presence of a mutant A1AT allele.”  Of 196 explanted livers from NASH patients, 21 (11%) has PASD+ globules; however, among NASH patients the frequency was 47%.  Also, the Z allele was present in 10% of all tested liver explants, this exceeds the 2% rate in the general population.  Thus, in agreement with other studies, A1AT heterozygosity contributes to chronic liver failure, but may affect fatty liver disease more than other chronic liver diseases.

Durability of HBsAg Loss in Hepatitis B AS Alawad et al. Clin Gastroenterol Hepatol 2020;18: 700-09.  In this retorspective study form NIH, 89/787 HBsAg-positive patients cleared HBsA; 65 had confirmed clearance. (spontaneous in 19, post-interferon in 22, and post-NA treatment in 24). 62 of 65 remained negative after a mean time of 9.6 years. 3 patients had seroreversion at a mean of 20 months after stopping therapy, though this was transient in 2 of 3 and may have been a false-positive.

Are Medications Contributing to Obesity and Fatty Liver Disease? ~25% of U.S. adults take a prescription medication  that often produces obesity as an adverse effect. (Hales CM et al. Obesity Week 2019, Link to Abstract T-OR-2037). PRESCRIPTION MEDICATIONS THAT PROMOTE WEIGHT GAIN: Prevalence of Use Among U.S. Adults, 2013-2016 Common obesogenic medications in this cohort, (n=11,055), included all glucocorticoids, beta-blockers, and antihistamines and some agents among antidepressants, antipsychotics, antidiabetics and progestin-only contraceptives.  Medications were defined as promoting weight gain according to the Endocrine Society Clinical Practice Guideline for the Pharmacological Management of Obesity (J Clin Endocrinol Metab, 2015).

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More fallout from Coronavirus: NY Times: Coronavirus May Add Billions to Nation’s Health Care Bill Insurance premiums could spike as much as 40 percent next year, a new analysis warns, as employers and insurers confront the projected tens of billions of dollars in additional costs of treating coronavirus patients.

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