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Porphyric Red Cells
Published in Ronald L. Nagel, Genetically Abnormal Red Cells, 2019
The synthesis of heme is partitioned between the mitochondria and cytosol of the cells. A number of different enzymes participate in the synthesis, making many diverse regulation mechanisms possible. Decreased activity of an enzyme leads to accumulation of the substrates before the block. Different enzyme defects will lead to accumulation of different substrates and to a variety of diseases called porphyrias. Overproduction of porphyrins and other precursors occur mainly in the liver and the erythroid marrow. In the erythorid marrow porphyrins will accumulate in the erythrocytes. Uroporphyrin, and to a lesser extent coproporphyrin, will accumulate in erythropoietic porphyria, free protoporphyrin will accumulate in erythropoietic protoporphyria, and zinc protoporphyrin will accumulate in erythrohepatic porphyria. Zinc protoporphyrin can also be synthesized in other nonhereditary diseases such as iron-deficiency anemia, anemia of chronic diseases, and lead intoxication.
Risk Assessment and Regulatory Toxicology
Published in Frank A. Barile, Barile’s Clinical Toxicology, 2019
The agency fulfills its mandate by setting standards established by regulations. For example, the OSHA Lead Standards for General Industry and Construction require employers to provide biological monitoring for workers exposed to airborne lead above the action level. Monitoring must be provided for lead and zinc protoporphyrin (or free erythrocyte protoporphyrin) in blood (see Chapter 24, Metals, for description). The employer is required to have these analyses performed by a laboratory that meets accuracy requirements specified by OSHA. The OSHA List of Laboratories Approved for Blood Lead Analysis is designed to provide a source to locate laboratories determined by OSHA to meet the requirements of the accuracy provisions of the lead standards. Laboratories voluntarily provide proficiency test data to OSHA for evaluation.
Cutaneous Porphyrias
Published in Henry W. Lim, Herbert Hönigsmann, John L. M. Hawk, Photodermatology, 2007
Gillian M. Murphy, Karl E. Anderson
The diagnosis of EPP rests on finding substantially increased amounts protoporphyrin in erythrocytes, with free protoporphyrin rather than zinc protoporphyrin accounting for the increase (Table 3). Transient fluorescence of red cells by fluorescence microscopy reflects this increase. Formation of zinc protoporphyrin is apparently depends on normal FECH activity. In the variant form of EPP in which FECH activity is normal, erythrocytes contain increased amounts of both free and zinc protoporphyrin. Erythrocyte zinc protoporphyrin is also increased in many other conditions affecting erythrocytes, such as some homozygous porphyrias, iron deficiency, lead poisoning, anemia of chronic disease and hemolytic conditions (52).
Hb Nouakchott [α114(GH2)Pro→Leu; HBA1: c.344C>T], A Second and Third Case Described in Two Unrelated Dutch Families
Published in Hemoglobin, 2018
Kirsten M. Pondman, Jacoline W. Brinkman, Hanneke M. van der Straaten, An K. Stroobants, Cornelis L. Harteveld
Hematological parameters were within normal range (Table 1). Proband A and his carrier father showed a low mean corpuscular Hb (MCH) level, but his sister, who is a non carrier, also showed a low MCH, which indicates that this is most likely not associated with the inheritance of the Hb variant. Proband B showed normal MCH, the normal zinc protoporphyrin (ZPP) values indicated the absence of iron deficiency. Haptoglobin levels were normal excluding hemolysis in Hb Nouakchott carriers. The HPLC pattern appeared normal, however, slightly asymmetric as far as the Hb A peak was concerned (Figure 1). There were no indications of β-thalassemia (β-thal) (normal Hb A2) or Hb variants (no clear extra peaks) [Figure 1(a)]. The CE pattern showed an Hb X fraction of 7.0–9.0%, eluting before Hb A (Table 1) [Figure 1(b)].
Porphyria: awareness is the key to diagnosis!
Published in Acta Clinica Belgica, 2022
Benjamin Heymans, Wouter Meersseman
Although protoporphyrias do have a very unique clinical presentation, a long delay in diagnosis is not uncommon [16]. These diseases can be identified by measuring the level of total erythrocyte protoporphyrins. An elevated level can arise in a wide variety of diseases such as anaemia of chronic disease and lead poisoning. Therefore, in case of elevation, the fractions of metal-free protoporphyrins and the zinc protoporphyrins should be determined. The proportion of zinc protoporphyrin to total erythrocyte protoporphyrin will be around 5% in EPP and between 20 and 40% in XLP [1]. Other diseases will have even larger proportion of zinc protoporphyrins (more than 50%). Finally, the diagnosis is confirmed by genetic mutation analysis.
Porphyrias and photosensitivity: pathophysiology for the clinician
Published in Postgraduate Medicine, 2018
Loukas Kakoullis, Stylianos Louppides, Eleni Papachristodoulou, George Panos
The reason behind this is that, unlike EPP, the erythrocyte protoporphyrin in lead poisoning and iron deficiency is not present as a free base but is chelated to zinc [81,82]. Zinc is an alternative metal substrate for ferrochelatase and can be incorporated into protoporphyrin, forming zinc-protoporphyrin (ZnPP) [19], which is far less phototoxic than metal-free protoporphyrin [83]. ZnPP is a normal metabolite found in trace amounts during normal heme synthesis [19], and in increased concentrations in iron deficiency, lead poisoning [76] and XLEPP [9].