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  • Brit. J. industr. Med., I966, 23, 83

    The Anaemia of Lead Poisoning: A Review H. A. WALDRON

    From the Medical Department, Vauxhall Motors Ltd., Luton, Beds.*

    Lead intoxication has been recognized as a clinical entity since ancient times. Hippocrates (370 B.C.) was probably the first person to associate lead with clinical symptoms, since when the harmful effects of lead on the body have been well documented. Early observations culminated in the brilliant monograph of Tanquerel des Planches (I839) in which the clinical aspects of the disease were completely outlined and most of the early signs of the disease were mentioned. So complete was this work that virtually nothing has been added to des Planches's observations since their publication. The earliest reference to lead anaemia was made in I83I by Laennec, who described thinness of the

    blood and pallor of the tissues in cases of lead poisoning at necropsy. The first direct evidence of the effect of lead on red blood cells was presented by Andral and Gavarret (I840), who counted the number of red blood cells in cases of lead poisoning and found the count to be much lower than normal.

    Since these early reports a great deal of work has been undertaken to try to discover the means by which lead causes anaemia, but it is probably true to say that at the present time this mechanism is still not fully understood. This review is an attempt to draw together at least some of the theories which have been advanced in the past and to present them, it is hoped, in an easily accessible manner for future workers in this field.

    Classification

    The anaemia of lead poisoning is seldom severe, the haemoglobin level rarely falling below 6o% or the red cell count below 4 x 106/c.mm. (Cantarow and Trumper, I944). There is a considerable varia- tion in the haemoglobin levels reported in the literature in cases of lead poisoning but the anaemia is usually said to be hypochromic. Thus Griggs (I964), in a study of 20 men with lead poisoning, found the anaemia to be mild and hypochromic with many reticulocytes and stippled cells present, although there was no correlation between the numbers of these cells and the degree of anaemia.

    Saita, Fiocchi, and Cattaneo (I952) made an extensive study of 41 cases of lead poisoning as a result of which they were able to classify the anaemia into three categories. In the pre-cinical stage the anaemia was normocytic and normochromic with hypochromia developing in the acute stage of the disease. A few patients in the acute stage tended to develop macrocytosis but as the disease moved into a chronic stage, half the patients had a macrocytic, hypochromic anaemia. In the other half the

    * Present address: 7 Elm Court, go Alcester Road, Moseley, Birmingham, I3.

    Received for publication October 6, I965.

    anaemia remained normocytic and normochromic. In children the anaemia is usually more severe and

    more pronouncedly microcytic and hypochromic, perhaps because lead poisoning in children is often associated coincidentally with a nutritional iron- deficiency disease (Watson, Decker, and Lichtman, I958). The anaemia of lead poisoning has many of the

    characteristics of thalassaemia from which it must be carefully differentiated. This is of particular im- portance in the Mediterranean countries where the incidence of thalassaemia is high. Most of the work in this connexion has been carried out in France or Italy (Saita and Moreo, 1959; Roche, Lejeune, Tolot, Mouriquand, Baron, Goineau, and Soubrier, I960; Gaultier, Fournier, and Gervais, I962; Gerard, Guerrin, and Roussel, I964). Differentia- tion between the two states lies mainly in demon- strating the presence ofhaemoglobin A2. In patients with thalassaemia this may be present in amounts up to io% whereas in the normal adult this type of haemoglobin amounts to less than 3%. Large amounts (40 to 90%) of foetal haemoglobin (Hb F) are also present in thalassaemia. There have been reports that Hb F is also found in cases of human lead poisoning and in lead-poisoned rabbits (Buczkowski, I964), but Lovisetto, Sibour, and

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  • Turco (I957) were unable to find it in I4 cases of plumbism, and Wolman and Bongiovanni (I956) in their review considered that only the normal adult haemoglobin (Hb A) was present in lead poisoning. A finding of excessive urinary coproporphyrin excretion will distinguish the patients with lead poisoning from those with thalassaemia. Lead anaemia has many of the features of a

    typical sideroblastic anaemia listed by MacGibbon and Mollin (I965), for example hypochromia, im- paired maturation and defective haemoglobinization of red cells, raised serum iron, rapid plasma iron clearance with decreased cell uptake of 59Fe, and erythroblasts containing iron-staining inclusion bodies (sideroblasts). It is classified as a sidero- blastic anaemia by Mollin (I965).

    Effects of Lead on Circulating Red Cells

    Osmotic Fragility A great deal of the early work on the pathogenesis of the anaemia of lead poisoning was carried out by Aub and his colleagues and reported in a series of classic papers (Aub, Reznikoff, and Smith, 1924; Aub, Minot, Fairhall, and Reznikoff, I924; Aub, Fairhall, Minot, and Reznikoff, I925; 1926). These authors found that normal washed or defibrinated red cells became more resistant to hypotonic saline after exposure to lead chloride solution. Cells that had been exposed to solutions of lead of concentrations as high as one part per ioo,ooo did not haemolyse in o-I% saline whereas normal cells were completely haemolysed in 0-25% saline. These observations on the effects of lead on the

    osmotic fragility of the red cell have been almost unanimously corroborated. Indeed the only dis- senting voice seems to be that of Sroczyn'ski who induced chronic and acute lead poisoning in rabbits by injecting a o9% solution of alkaline lead acetate into the marginal vein of the ear (Sroczynski, I959, I963) and found that red cells from both groups of animals showed a marked decrease in resistance to hypotonic saline solutions. The resistance was decreased more markedly in the acute group than in the chronic group. Many other authors, however, have recorded a normal or increased resistance to hypotonic saline solutions (Pearse, I926; Velicogna, 1933; Fullerton, 1952; Baron, 1954; Harris and Greenberg, I954; Crepet, Rubino, and Gobbato, I956; Rubino, Prato, and Fiorina, I956; Clarkson and Kench, I958b; Griggs and Harris, I958; Tishkoff, Granville, Rosen, and Dameshek, I958), and the findings of Aub and his colleagues may be taken as being well confirmed.

    Fullerton (1952), in her study of eight patients with plumbism, found that quantitative changes in

    fragility curves were altered pari passu with an increase in punctate basophil counts, but this observation has not been confirmed since. The changes in osmotic fragility induced by lead are, on the whole, slight, although the osmotic fragility of leaded red cells is more increased after sterile incu- bation for 24 hours (Harris, I963; Griggs, I964; Waldron, I964). The mechanism by which lead causes osmotic

    changes in red cells is not as yet understood. Lead affects the cation permeability of the cell membrane resulting in increased potassium loss (Joyce, Moore, and Weatherall, I954; Vincent and Blackburn, 1958). At concentrations of ioo JM/l., K+ loss is much increased, the effect decreasing with time (Passow and Tillmann, I955). It is thought that the increased osmotic resistance may indicate that more water could enter the cells before a critical spheroidal form is reached and lysis occurs (Griggs, I964), and it may be possible to equate the changes in osmotic fragility with the alterations in permeability since changes in permeability may affect the water relations of the cell.

    Mechanical Fragility Although Aub and his colleagues found that the osmotic fragility of the leaded red cell was decreased, they found, by con- trast, that the mechanical fragility was much in- creased. Thus, when leaded red cells were rotated in a tonometer or centrifuged, haemolysis due to the rolling of the red cells on the glass was markedly increased compared with normal red cells similarly treated. Shaking the cell suspensions in a shaking machine gave similar results. This double action of lead-decreasing the osmotic fragility whilst in- creasing the mechanical fragility-had also been seen by Fici (I920, I92Ia and b). From their observations Aub et al. concluded that

    leaded red cells were less able to withstand the dynamic trauma consequent upon passage through the capillaries and so broke up more readily than normal cells, giving rise to the anaemia seen in lead poisoning. This conclusion was in accord with the general concensus of opinion at the time, since early work by Heubel (I87I) and Bouchard (I873), later confirmed by Rauch (I922), had indicated that lead anaemia was due to the destruction of circulating red cells. Aub and Reznikoff (1924) proposed that the

    damage to the red cell envelope which brought about the increased mechanical fragility was caused by the liberation of free acid when lead combined with the inorganic phosphate of the red cells or plasma according to the following equation 3PbCl2 + 2Na2HPO4 =

    Pb3(PO4)2 + 4NaCl + 2HCI.

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