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Table of Contents
Definition / general | Clinical features | Uses by pathologists | Microscopic (histologic) images | Positive staining - normal | Positive staining - diseaseCite this page: Pernick N. Alkaline phosphatase. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/stainsalkphos.html. Accessed May 24th, 2019.
Definition / general
- Membrane bound glycoprotein with hepatic, osseous, renal and placental isoenzymes
- See also PLAP-placental alkaline phosphatase
- Tissue-nonspecific alkaline phosphatase (TNAP) plays a key role in bone mineralization by degrading inorganic pyrophosphate and providing free inorganic phosphate
- TNAP gene defect causes hypophosphatasia, characteristic of systemic skeletal hypomineralization
- Surgical pathology applications discussed below
Clinical features
- May be affected by ABO loci and obesity (BMC Genomics 2013;14:684)
- Elevated alkaline phosphatase screens for Vitamin D deficiency, although rarely alkaline phosphatase is normal (Clin Pediatr Endocrinol 2013;22:73)
- Bone alkaline phosphatase is associated with acute myocardial infarction in a population with high prevalence of hypovitaminosis D (Clin Chim Acta 2013;425:192)
- May predict outcome in alcoholic hepatitis (Biomed Res Int 2013;2013:614081)
- Higher serum levels in patients with chronic kidney disease stages 3-4 are associated with higher mortality and end stage renal disease (Am J Kidney Dis 2013;62:703)
Uses by pathologists
- Component of an alternative method in immunohistochemistry, click here
- Muscle biopsies uses an enzymatic technique
- Use frozen tissue (protocol from IHC World)
- In inflammatory myopathies, appears to “spill out” from capillaries into interstitium due to increased vascular permeability
- Also a marker for regenerating myofibers
- Osteoblasts (active)
- Often labeled using naphthol phosphate and the diazonium dye fast blue to demonstrate alkaline phosphatase enzyme activity directly, present on apical (secretory) cell membrane
- Confirms diagnosis of giant cell tumor of bone (Virchows Arch A Pathol Anat Histol 1978;378:287)
Microscopic (histologic) images
Images hosted on other servers:
Muscle: various images
Muscle: immature
small fibers have
cytoplasmic staining
Positive staining - normal
- Cardiac muscle, smooth muscle
- Endothelial cells: sites of alkaline phophatase activity appear red, nuclei stain blue
- Osteoblasts
Positive staining - disease
- Giant cell tumor of bone and soft tissue, mononuclear stromal cells (Hum Pathol 2005;36:945)
- Muscle: regenerating fibers, immature muscle fibers, proliferative connective tissues
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