70 POST GRADUATE. MEDICAL JOURNAL February 1948

and of the State, and although it must be agreedthat the care of rheumatic children deserves thefirst consideration, there is every justification toset up a system of cardiac clinics based on anation-wide organization for the benefit of cardiaccases of any type.The crippling effect of rheumatic heairt disease,

the growing incidence of arterial hypertensive

disease and of the degenerative cardio-vasculardisease generally call for a comprehensive schemeproviding up-to-date diagnostic and remedialfacilities, as well as after-care and rehabilitation forall cases of cardio-vascular disese.

I beg to extend my sincere thanks to Dr. MauriceDavidson for his criticism and helpful advice in thepreparation of this article.

HAEMOLYTIC ANAEMIA, WITH PARTICULARREFERENCE TO CAUSE AND^ MECHANISM

By J. V. DACIE, M.B., M.R.C.P. (LOND.)Department of Pathology, British Post Graduate Medical School, London

The anaemias resulting from abnormally rapidhaemolysis constitute an important group of dis-orders of great interest to both clinician.and path-ologist, but although considerable progress towardstheir understanding has been made in recentyears, much is still unexplained. In this shortreview general principles are first considered, then,choosing certain important types of haemolyticanaemia as examples, the various mechanisms ofcausation are discussed. Recent work of im-portance is mentioned as far as possible and someof the many points still requiring elucidation areindicated.

The Results of Increased Haemolysis(a) Increased blood pigment excretionThe essential feature of haemolytic anaemia,

however caused, is a shortening of the life of thered blood cell, now known with certainty to benormally about 120 days. In health, therefore,about o.85 per cent. of the circulating red cells areeliminated from the circulation daily; in hae-molytic anaemia, however, the rate of destructionmay be increased tenfold or more.The result of this unusually rapid haemolysis is

a greatly increased excretion of bile pigment,almost invariably accompanied by jaundice. Theexcess bilirubin in the plasma gives a Van denBergh reaction of the indirect type. In thefaeces, the content of bile derivatives, usuallymeasured as ' urobilinogen,' is above the normaldaily figure of 8o to 250 mgm. The urine generallycontains no bilirubin-the jaundice is ' acholuric,'and only traces of urobilinogen.

In some less common types of haemolyticanaemia blood destruction takes place mainly inthe circulating blood stream, and blood pigmentmay appear in the urine (haemoglobinuria). Inthe more common types in which haemolysisseems to take place chiefly in backwaters of themain blood stream, such as within the splenicpulp, haemoglobinuria is not seen. In the formerinstance the patient's plasma may contain con-siderable amounts of oxyhaemoglobin and methae-malbumin, the haemoglobin in the urine beingderived from the plasma oxyhaemoglobin.(b) Compensatory red cell regeneration; the bone

marrow and the peripheral blood picture inhaemolytic anaemia

Increased haemolysis leads invariably to in-creased red cell formation within the bone marrow,at least after the first few days of a haemolyticattack, and equilibrium between destruction andformation may be eventually attained. Usually,however, the red cell count is well below normal.Many patients stabilize with haemoglobin levelsbetween 5o and 8o per cent.

This increased marrow activity is accompaniedby a centrifugal spread of red marrow into the longbones and a partial or complete disappearance offat spaces from large areas of marrow, which be-comes increasingly hyperplastic and erythro-cytogenic. The presence in the peripheral bloodof an increased proportion of reticulocytes isevidence of this. The reticulocyte count mayindeed reach very high levels; sometimes asmany as 50 per cent. of the red cells, or evenmore, are in this form. Macrocytosis is commonly

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February 1948 DACIE: Haemolytic Anaemia, with Particular Reference to Cause 71

TABLE I

THE DUAL PATHWAY OF INCREASED BLOOD PIGMENT EXCRETION IN HAEMOLYTIC ANAEMIA (A SIMPLIFIED SCHEME)

Haemoglobin(intracorpuscular)

Less rapid haemolysis Rapid 'intravascular' haemolysis

Bilirubin-globin 'Haemoglobinaemia'(in plasma) (oxyhaemoglobin in plasma)

Liver Methaemalbuminaemia Haemoglobinuria(methaemalbumin in plasma) (haemoglobin in urine)

Bilirubin ? Bilirubin(in bile)

Urobilinogen(in faeces)

encountered. The cause of this change is un-certain: it may depend in part, at least, upon theincreased percentage of reticulocytes present. Itis not modified by liver therapy. There may beconsiderable anisocytosis but poikilocytes are notusually seen, the even roundness and full haemo-globin content of the red cells in haemolyticanaemia being often a striking feature. Micro-spherocytes are often, but not invariably, present.Nucleated red cells are sometimes seen in theperipheral circulation and have been thought toindicate extra-medullary erythropoiesis. Theyare, however, rarely present in large numbers(erythroblastaemia). They occur most commonlywhen the patient is an infant or child; lessfrequently in an adult (Fig. i). Immature leu-cocytes in considerable numbers may rarely bepresent in the peripheral blood (leukaemoidreaction).

Red Cell Destruction in Health and DiseaseA real understanding of the causes and mech-

anisms of red cell destruction in health would bea great help in the elucidation of what may happenin disease. Unfortunately, even less is known ofthe former than of the latter. There are four mainhypotheses: (a) that red cells are eliminated fromthe circulation due to the phagocytic activity ofreticulo-endothelial cells, (b) that the mechanicaltrauma to the cells resulting from continuousrapid circulation eventually ruptures the red cellenvelopes, (c) that auto-antibodies or chemicalhaemolysins are responsible and (d) that destruc-tion is due to the effects of stasis in the spleen andelsewhere. The truth is obscure; perhaps someor all the above mechanisms play an integrated

part. In disease, the mechanism may be moreobvious. For instance, erythrophagocytosis maybe conspicuous in the spleen and in lymph glands,and even in the peripheral blood stream (Fig. i).Even here the probability is that it is a secondaryphenomenon, the cells phagocytosed having beenpreviously damaged by antibody or haemolyticchemical. Certain types of pathological cells suchas microspherocytes, sickle cells and probably allpoikilocytes and agglutinated cells have beenshown to be more easily ruptured than normal bymechanical means. The importance of auto-antibodies is being increasingly revealed; theirdevelopment is responsible for haemolytic diseaseof the newborn and many examples of acquiredhaemolytic anaemia. Stasis within the spleen isprobably an important cause of blood destructionin familial haemolytic anaemia (acholuric jaundice).The truth is that haemolytic anaemia may be

caused by a variety of mechanisms, about whichenough is now known to justify a pathogeneticclassification. Although incomplete and tentativethis is preferable to a clinical grouping or one basedpurely on morphological haematology.

Classification of Haemolytic AnaemiasIn the following classification (Table 2) the

primary division is between an intrinsic (con-genital or acquired) and an extrinsic origin, theformer group being divided into those disorders inwhich the primary abnormality seems to be in-herent in the red cells themselves and into thosein which the plasma and/or tissues of the patientcontain a haemolytic substance secondarily affect-ing the red cells.

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72 POST GRADUATE MEDICAL JOURNAL February I948

* .>;. ...p.

. .,.

4.0* * f .

FIG. I.-Photomicrograph of a blood film from a woman,aged 30, suffering from acquired haemolytic anaemia.Microspherocytosis, erythroblastaemia and erythro-phagocytosis are well shown. The 'Coombs Test' for' incomplete' antibody was positive. The patient hadrelapsed after a temporary remission following splenec-tomy Is months previously. Jenner-Giemsa X 500.

FIG. 2.-Photomicrograph of a blood film from a womanaged 24 with acquired haemolytic anaemia. An auto-haemolysin was present in her serum and an autohae-magglutinin active at 370 C. The photograph showsintense autohaemagglutination and also erythrophago-cytosis. Jenner-Giemsa X 6oo. .

FIG. 3.-Photomicrograph of a blood film from a womanaged 6i suffering from polycythaemia vera. She hadreceived an overdose of acetylphenylhydrazine duringthe course of treatment. The photograph shows con-traction and distortion of the red cells and abundantbasophilic stippling. Jenner-Giemsa X 6oo.

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February 1948 DACIE: Haemolytic Anaemia, with Particular Reference to Cause 73

TABLE 2

A PATHOGENETIC GROUPING OF HAEMOLYTIC ANAEMIA(I) Intrinsic Origin (congenital or acquired disorders).

A. Due to increased sensitivity of the patient'scorpuscles to normal mechanisms. The faultlies in the cells themselves.

B. Due to the development of an abnormalhaemolytic mechanism. The fault lies in thepatient's plasma or tissues; the red cells areprimarily normal, but may be secondarilyaltered.

(2) Extrinsic Origin. Due to the effects of drugs,chemicals or toxins.

Important haemolytic anaemias belonging toGroup iA of Table 2 are listed in Table 3. Herealso might be classified pernicious anaemia andthalassaemia (Cooley's anaemia). In these latterdisorders there is an undoubted haemolytic ele-ment, possibly secondary to the production ofabnormally shaped cells (poikilocytes).

TABLE 3IMPORTANT TYPES OF HAEMOLYTIC ANAEMIA DUE TOCORPUSCULAR ABNORMALITIES INCREASING THE CELLS'SENSITIVITY TO NORMAL HAEMOLYTIC MECHANISMSI. Familial haemolytic Congenital origin. Abnor-

anaemia (acholuric mal corpuscles, evidencedjaundice). by microspherocytes and

increased fragility. Noplasma abnormalities. Nor-mal cells survive normallyafter transfusion into pa-tients. Patient's cells sur-vive badly in normal reci-pients.

2. Sickle cell anaemia. Constitutional origin. Ab-normal corpuscles sickledby anoxia. No plasmaabnormalities.

3. Nocturnal haemo- An acquired disorder. Ab-globinuria.' normal corpuscles evidenced

by in vitro lysis in normalsera. Exact abnormality notdetermined. No plasmaabnormalities. Normal redcells survive well after trans-fusion into patients.

In Table 4 are listed examples of haemolyticanaemia in which an abnormal haemolytic mech-anism is known to be the cause of the red celldestruction (Group iB of Table z). Auto-anti-bodies can be demonstrated adsorbed on to. thered cells and sometimes in the plasma.

TABLE 4TYPES OF HAEMOLYTIC ANAEMIA DUE TO AN ABNORMALHAEMOLYTIC MECHANISM, I.E., DUE TO THE PRESENCE

OF ANTI-CORPUSCULAR ANTIBODIES.I. Acquired haemolytic Not congenital or inherited.

anaemia. Corpuscular abnormalitiesinconstant, probably notprimary. Auto-antibodiesmay be present in plasma;

probably always demon-strable on cells.Antibodies usually of the'incomplete' type. Auto-agglutinins sometimes pre-sent; autohaemolysinrarely demonstrable. Nor-mal cells survive badly inpatients after transfusion,i.e., they are affected bysame haemolytic mechan-ism as are the patient's ownred cells.

2. Haemolytic disease Corpuscular abnormalitiesof the Newbom (spherocytosis and increased(erythroblastosis fragility) may be present,foetalis). but not probably primary.

Rh auto-antibodies (de-rived from mother) rarelydemonstrable in plasma, butincomplete ' Rh antibody

probably always demon-strable adsorbed on to theaffected cells. Normal cells(Rh+) often rapidly eli-minated after transfusion.

3. 'Cold' haemoglo- Corpuscles normal. Auto-binuria. haemolysin and haemag-

glutinin absorbed from theplasma on to red cells whenblood is chilled.

Representative haemolytic disorders due to theaction of extrinsic agents (Group 2 of Table 2) aregiven in Table 5.

TABLE 5EXAMPLES OF HAEMOLYTIC ANAEMIAS DUE TO ExTRINSIC

CAUSESi. Due to Drugs and Chemicals.

E.g., Sulphanilamide, phenylhydrazine, arsine.2. Due to Bacterial Toxins.

E.g., Cl. welchii haemolysin (as in puerperal 'gasgangrene ').

Mechanism of Haemolysis in HaemolyticAnaemiasIn this section will be considered the evidence

which has been held to justify the grouping to-gether of the anaemias listed in Table 3.(A) Importance of red cell abnormalities

Infamilial haemolytic anaemia several manifesta-tions of abnormality of the red cells may bedemonstrated. Most well known is the increasedosmotic fragility, which. has been repeatedlydemonstrated since first observed by Chauffard40 years ago; this increase in fragility is held to beassociated with the abnormally spheroidal shape ofthe cells (microspherocytosis). The red cells mayalso be observed to undergo unusually rapidspontaneous haemolysis when incubated in vitrounder sterile conditions (Dacie, I941), and to beabnormally sensitive to the haemolytic action oflysolecithin (Singer, I941) and to the effect of

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POST GRADUATE MEDICAL JOURNAL

mechanical trauma (Shen, Castle and Fleming,I944). No abnormalities or antibodies are presentin the patient's plasma. The above types ofcorpuscular abnormality which may be demon-strated in vitro seem to be associated with unusualsensitivity to the action of the spleen-the actualstagnation of blood within the organ may well con-tribute to this in vivo haemolysis. After splen-ectomy the cellular abnormalities may be lessmarked, but rarely disappear. In the absence ofthe spleen, however, they seem to be relativelyunimportant, for the rate of corpuscular break-down becomes normal or, if not entirely normal,is easily compensated for. The red cell count andhaemoglobin content soon rise to the normallevels. The results of transfusion experimentsclosely parallel in vitro findings. It has beenshown that normal red cells survive well in thesepatients, but the patients' corpuscles both beforeand after splenectomy are rapidly destroyed innormal recipients (Dacie and Mollison, I943).Many similarities exist between sickle ceil

anaemia and familial haemolytic anaemia. Inboth disorders the fundamental abnormality re-sides in the red cells themselves. There is an un-explained alteration in the shape of the corpusclestowards sickled forms whenever the level of re-duced haemoglobin within the cells increasesabove a certain critical, but variable, level. Theincreased rate of haemolysis in vivo is probablydue to two factors. The mechanical fragility ofsickled cells is considerably increased and actualvascular obstruction may result from the clump-ing of sickled cells. The patients' plasma isnormal. Nocturnal haemoglobinuria is a rare butmost interesting form of haemolytic anaemia. Oncemore the corpuscles themselves are at fault. Theexact abnormality is, however, obscure; perhapsthe cell membranes are defective. The corpusclesbehave as if sensitized with haemolytic ambo-ceptor, for they are readily haemolyzed in vitroby thermolabile components of normal serum(complement), and in vivo by the patient's ownplasma. In vitro tests demonstrate that noabnormal antibody exists in the patient's plasma.This has been confirmed by the good survival oftransfused normal cells (Mollison, I947).(B) Importance of plasma abnormalities (auto-

antibodies)In Table 2, Group iB, are listed three important

types of haemolytic anaemia. That termed' acquired haemolytic anaemia ' has recently re-ceived a good deal of attention and ways of dis-tinguishing cases from familial haemolytic anaemia,which it may closely simulate clinically, have beendiscovered (Loutit and Mollison, 1946). Acquiredhaemolytic anaemia results from the develQpmentof auto-antibodies capable of damaging the

patient's own red cells and accelerating the rateat which they are eliminated from the circulation.The ultimate cause of this auto-antibody forma-tion is quite unknown at the present time. Severaltypes of antibody may be present. The mostfrequent and important kind seems to be the so-called ' incomplete' antibody, best detected byagglutination of corpuscles on to which thisantibody, a globulin, has been absorbed by ananti-human-globulin serum prepared in a rabbit(Coombs, Mourant and Race, 1945). The resultof this ' Coombs test ' is of great importance indiagnosis. The positive results in acquired hae-molytic anaemia contrast with the negative resultsobtained in the familial disease. Incompleteantibody' free' in the plasma is seldom detected;presumably it is usually continuously adsorbed onto corpuscles as fast as it is formed. Autohae-magglutinins of the more usual type are sometimes,but inconstantly, present. They are mostly 'coldagglutinins' and seldom active at 370 C. Auto-haemolysins are rarely demonstrable. More thanone type of antibody effect may be observed in thesame patient, incomplete antibody and a hightitre cold auto-agglutinin for instance. Clinicallythe severity and course of the disorder are mostvariable. Those cases in which haemolysins aredemonstrable are particularly severe, and therapid intravascular haemolysis may be associatedwith haemoglobinuria. Transfusions with normalblood are of transient benefit; the transfusedcells are destroyed rapidly in much the same wayas are the patient's own cells (Mollison, 1947).This poor survival is of diagnostic importance andis in striking contrast with the good survival oftransfused blood in familial haemolytic anaemiaand in nocturnal haemoglobinuria where the faultlies entirely in the patient's corpuscles.

Alterations in corpuscular morphology are oftenencountered in acquired haemolytic anaemia;macrocytosis is frequent and there is often, butnot invariably, spherocytosis and increased fragilityof varying grades (Fig. i). These phenomena areprobably secondary events. They sometimes leadto errors in diagnosis. The cause of the increasedfragility is obscure ; in vitro exposure of cells tothe action of agglutinin and haemolysin does notseem to affect fragility. The role of the spleen islikewise uncertain; it is enlarged and palpable,but the enlargement is not on the whole as greatas in familial cases. Splenectomy is the onlyknown line of treatlnent and is often performed.It is usually followed by improvement, and some-times complete remission. The outlook is, how-ever, uncertain, and the progress of the diseasemay be hardly influenced. This is not to bewondered at, for the cause of the red cell destruc-tion does not reside primarily within the spleen.

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February 1948 DACIE: Haemolytic Anaemia, with Particular Reference to Cause 75

rhe organ may, however, contribute to hae-nolysis, by being a source of antibody and by re-moving damaged cells from the circulation. The-nding of activities of this nature may explain therariable benefits which may follow splenectomy.The exact manner in which ' incomplete' anti-

body causes haemolysis in vivo is not yet clear.[t has been suggested that auto-agglutinated cellsire filtered off from the circulation in the spleennd elsewhere, or that the increased mechanicalFragility of agglutinated cells may determine theirdestruction. Further evidence on these points isrequired. The ' cold' auto-agglutinins activeDnly at temperatures below body temperature areprobably of no importance; they may perhaps beooked upon as additional manifestations of thegeneral tendency to auto-antibody development.[f active at body temperature thay may wellcontribute to haemolysis, but this is rare (Fig. z).A,utohaemolysins act by damaging the corpuscular;urfaces and allowing them to be destroyed bymzyme systems in the plasma (complement).Haemolytic disease of the newborn. Many of the

'eatures of acquired haemolytic anaemia are re-?roduced in this disorder. Haemolysis is due to:he action of antibodies, which may be agglutininsr incomplete antibodies. In haemolytic disease)f the newborn, however, the development oftntibodies is not autogenous in the infant; theyire of maternal origin, being developed prior to thenfant's birth as a result of differences in cor-)uscular Rh antigens between the unborn infantnd the mother. Foetal corpuscular antigens,nter the maternal circulation and cause the mother:o develop antibodies. These antibodies re-,rossing the placental barrier damage the foetal*ed cells. This sequence of events is so well known:hat a further discussion would be out of place here.[t may be added, however, that as in acquirediaemolytic anaemia the exact way in which themntibodies cause destruction of the infant's cellsn vivo is far from clear.Cold haemoglobinuria is a rare but characteristic

lisorder, usually associated with syphilis, oftenmongenital in type. Intravascular haemolysis andiaemoglobinuria occur in episodes, and are)rought on by the patient becoming chilled. Inhe patient's plasma are found ' cold' antibodiesauto-agglutinins and autohaemolysins) which areLbsorbed on to corpuscles at relatively low temper-Lture, as might be found within the cutaneousressels in the limbs on a really cold day. Thetutohaemolysins damage the corpuscular mem-)ranes so that the cells become lysed by plasma

enzymes (complement), when they circulate oncemore within areas of the circulation where thetemperature is at or near 370 C.(C) Effects of drugs and chemicals

In Table 5 are listed representative drugs,chemicals and bacterial toxins, all capable ofcausing haemolysis. The exact way in whichsome of these drugs and chemicals work is againobscure. Sulphanilamide for instance is inert invitro and usually in vivo; its occasional hae-molytic action in vivo has been thought to be dueto the development of unusual derivatives, some ofwhich have been shown to cause increased fragilityand ultimately haemolysis in vitro (Emerson, Hamand Castle, 194I).Phenyhydrazine and acetylphenylhydrazine

regularly cause haemolysis in vivo. Morphologicalevidence of their damaging actions on the red cellscan be seen in blood films. Contracted and dis-torted cells and considerable basophilic puncta-tion may be observed when large doses are given(Fig- 3).

In Cl. welchii septicaem.ia intense haemolysismay develop, this appears to be due to the actionof the a toxin, a lecithinase, on the red cellenvelopes.

-SummaryHaemolytic anaemia in man is a syndrome of

varying causation. A brief description of the maineffects of increased haemolysis has been given andthis is followed by a tentative grouping of well-known types of haemolytic anaemia into threeclasses. The primary division is into those ofintrinsic and into those of extrinsic origin. Theformer is subdivided in those disorders in whichincreased haemolysis seems to be due to cor-puscular abnormalities, and into those in which anabnormal haemolytic mechanism is primarilyresponsible.

This pathogenetic classification is followed by aconsideration of the mechanism of haemolysis incertain well-known types of haemolytic anaemia.

BIBLIOGRAPHY

COOMBS, R. R. A., MOURANT, A. E. and RACE, R. R. (1945)Brit. J3. Exp. Path., 36, 255.

DACIE, J. V. (I941), . Path. Bact., 52, 331.DACIE, J. V. and MOLLISON, P. L. (1943), Lancet i, 550.EMERSON, C. P., HAM, T. H. and CASTLE, W. B. (I94I),

Y. Clin. Invest., 20, 451.LOUTIT, J. F. and MOLLISON, P. L. (1946), 7. Path. Bact.,

58, 7I1.MOLLISON, P. L. (I947), Clin. Sci., 6, 130.SHEN, S. C., CASTLE, W. B. and FLEMING, E. M. (I944),

Science, I00, 387.SINGER, K. (I940), Amer. .7. Med. Sci., I", 466.

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