Macroamylasemia

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Macroamylasaemia is the presence of serum amylase of a large molecular size, seen in both otherwise healthy individuals, and also in various diseases. Amylase seems to be able to self-polymerise and/or form ~~immune~~ complexes with other blood proteins, e.g. immunoglobulins.

Epidemiology

Macroamylasaemia is found in ~1% normoamylasaemic individuals and up to 2.5% in those with hyperamylasaemia ⁴. It has been found more commonly in men and the middle-aged but this is based on limited datasets.

Pathophysiology

Macroenzymes are not uncommon on laboratory assays of human blood. Many proteins self-polymerise or form complexes with other proteins, which are normal constituents of blood, e.g. globulins, carrier molecules, etc ⁵.

The normal amylase molecule has a molecular weight of 45 kDa, but in macroamylasaemia the amylase forms a complex with globulin forming a much larger macromolecule ~200 kDa. Normal non-complexed amylase is freely filtered at the renal glomerulus and although most is reabsorbed in the tubules ~25% is excreted in the urine. However in macroamylasaemia the molecule is too large to be filtered by the kidney resulting in a normal urinary amylase despite an elevated serum amylase ³.

Interpretation

This condition can be confused with other causes of raised serum amylase (e.g. acute pancreatitis). Macroamylasaemia is accompanied by normal serum lipase and urinary amylase levels. By contradistinction, in pancreatic disease the serum lipase will usually be elevated as well ².

Causes of macroamylasemia

liver disease
diabetes mellitus
malignancy
malabsorption
autoimmune disorders
infusion of hydroxyethyl starch (HES)

History and etymology

~~Macroamylasaemia~~Macroamylase was first described in 1964 by Wilding. The term 'macroamylasaemia' was coined by Berk et al. in 1967 ⁴.

-<p><strong>Macroamylasaemia </strong>is the presence of <a href="/articles/amylase-1">serum amylase</a> of a large molecular size, seen in both otherwise healthy individuals, and also in various diseases. Amylase seems to be able to self-polymerise and/or form immune complexes with immunoglobulins.</p><h4>Epidemiology</h4><p>Macroamylasaemia is found in ~1% normoamylasaemic individuals and up to 2.5% in those with <a title="Hyperamylasaemia" href="/articles/amylase-1">hyperamylasaemia</a> <sup>4</sup>. It has been found more commonly in men and the middle-aged but this is based on limited datasets. </p><h4>Pathophysiology</h4><p>The normal amylase molecule has a molecular weight of 45 kDa, but in macroamylasaemia the amylase forms a complex with globulin forming a much larger macromolecule ~200 kDa. Normal non-complexed amylase is freely filtered at the renal glomerulus and although most is reabsorbed in the tubules ~25% is excreted in the urine. However in macroamylasaemia the molecule is too large to be filtered by the kidney resulting in a normal urinary amylase despite an elevated serum amylase <sup>3</sup>. </p><h4>Interpretation</h4><p>This condition can be confused with other causes of raised serum amylase (e.g. <a href="/articles/acute-pancreatitis">acute pancreatitis</a>). Macroamylasaemia is accompanied by normal serum <a href="/articles/lipase">lipase</a> and urinary amylase levels. By contradistinction, in pancreatic disease the serum lipase will usually be elevated as well <sup>2</sup>.</p><h4>Causes of macroamylasemia</h4><ul>
+<p><strong>Macroamylasaemia </strong>is the presence of <a href="/articles/amylase-1">serum amylase</a> of a large molecular size, seen in both otherwise healthy individuals, and also in various diseases. Amylase seems to be able to self-polymerise and/or form complexes with other blood proteins, e.g. immunoglobulins.</p><h4>Epidemiology</h4><p>Macroamylasaemia is found in ~1% normoamylasaemic individuals and up to 2.5% in those with <a href="/articles/amylase-1">hyperamylasaemia</a> <sup>4</sup>. It has been found more commonly in men and the middle-aged but this is based on limited datasets. </p><h4>Pathophysiology</h4><p>Macroenzymes are not uncommon on laboratory assays of human blood. Many proteins self-polymerise or form complexes with other proteins, which are normal constituents of blood, e.g. globulins, carrier molecules, etc <sup>5</sup>. </p><p>The normal amylase molecule has a molecular weight of 45 kDa, but in macroamylasaemia the amylase forms a complex with globulin forming a much larger macromolecule ~200 kDa. Normal non-complexed amylase is freely filtered at the renal glomerulus and although most is reabsorbed in the tubules ~25% is excreted in the urine. However in macroamylasaemia the molecule is too large to be filtered by the kidney resulting in a normal urinary amylase despite an elevated serum amylase <sup>3</sup>. </p><h4>Interpretation</h4><p>This condition can be confused with other causes of raised serum amylase (e.g. <a href="/articles/acute-pancreatitis">acute pancreatitis</a>). Macroamylasaemia is accompanied by normal serum <a href="/articles/lipase">lipase</a> and urinary amylase levels. By contradistinction, in pancreatic disease the serum lipase will usually be elevated as well <sup>2</sup>.</p><h4>Causes of macroamylasemia</h4><ul>
-</ul><h4>History and etymology</h4><p>Macroamylasaemia was first described in 1964 by <strong>Wilding</strong>. The term 'macroamylasaemia' was coined by <strong>Berk </strong>et al. in 1967 <sup>4</sup>.</p>
+</ul><h4>History and etymology</h4><p>Macroamylase was first described in 1964 by <strong>Wilding</strong>. The term 'macroamylasaemia' was coined by <strong>Berk </strong>et al. in 1967 <sup>4</sup>.</p>

References changed:

5. Taes YE, Louagie H, Yvergneaux JP, De Buyzere ML, De Puydt H, Delanghe JR, Lott JA. Prolonged hyperlipasemia attributable to a novel type of macrolipase. (2000) Clinical chemistry. 46 (12): 2008-13. <a href="https://www.ncbi.nlm.nih.gov/pubmed/11106339">Pubmed</a> <span class="ref_v4"></span>