An Address on SYMPTOMS AND PATHOGENESIS OF THE HAEMORRHAGIC DIATHESIS
Authors: H. L. Tidy
Journal: BMJ (1930)

TilE term "l haemorlrhagic diatlhesis " is applied to a coni- ditioPini u'-lhich, iithout cause, extr-avasation of blood tendcls to take pmlace into the skin an(d from the mltucous mnlenibr-anes.The group in the p)ast has been u-sually known by tlhe naame of piimaiiy puirpura," but numerous other terms have been emiiployed.Pur puira is the m-lost str iking featurie of the group, sinice its occurrence as a primary symTtom is conifinied to this entity, but it is not invariably or Iecss'larilv' present.The essential clharacteristic of tle dlisease is tlhe tendenvcy to sl)ontaneous liaenmorrhlages, and the nature of these milay be-veliy varied.In secondarv pulrpura the symptomatology may he identical, but somiie recognizable primar y disease is present.Haemophilia, however, is a syndrome of a different nature. PATHOGENESIS.Thie cause of these haemorrhages is still in douibt.Various orglias and tissues hiave been lhel(d to be initially at fault, and the influeimce and action of these will he consider-ed beloW-.Tin (re.sedl (.oalla.ryPerieac ility.-Thosm.all size of niann of time cutaineous haemorrhages leaves no doubt that the blood hias esca'ped fronm the capillaries.It is well kniownl tlhat the blood cells ar-e able, il ceitain circumstances, to traverse tlhe walls of these vessels.An inicr eagse in thle permeability of time elidotlieliulim of tle cal)illaries, on eaelling a certain stage, wvoull p)erlmit the blood cells to escape throulgh the vessel walls in suich a degree as to result ill tlhe app-earance of ctutanieous and other haemior- I'llS, clejmeiidiiig Ol tile site anild extent of the chlange.Is tIlCeIe ally evi(leilce for time o(clcluence of suiell undul.3permeability in tle lhae:emoi'lla(ric diathiesis?As the perme- ah)ility iner-eases from its niormial grade it will rekach a poinit at whflich it permits tile ')assage of an increased amount of plasma, but not of cells.Accumulations of suclh plasilla miuilst manifest themselves as wlheals, local oedema of the tissu.es,and urticai'il.Lewis, 14 ill his stud(ly of tlhe blood vesssels of tile skiln, ca1ine to tle conclusion tihat skin stiiuiiilatioi prodliiees w'hleals by causilig active dilatationl andh incresea(d permeabilitv of tiie miinuto endothelial vessels.The fluid pIresent w-as proved to be blood plasma.Tfllerefore, if incr-eased permeability is the cause of primary liaemiiorrhlnages, we wolil(l exlect in time Iliaeniorrllagic diatlmesis to finid the occurrencee 'of local oedeiias and urticaria.It is oell recognized that this is so.Clinically, in certain types of the haemorrhagic diathesis, thlere is close relatioishilip between tlle occurrence of wiealas an(l urticaria, an(l tlhe occurrence of purpur a and ecehlv-Moses.For examl)le, in a given individual attacks of urtiearia and of lmaenmorrhages mayv alternate, or both may be p)resent sinlultaneouslv.This is referried to further under " Svmptomato1ogy."Obviously it many be accepted thlat in such cases tile formllation of whmeals aiid of urticaria, and( the occurrence of liaenlorrlrag'es, ar e (lue to the same factors.A strikillng pblenlomelnon to whlieil Lewis called itteimtion is the occuirence of " refractoriness " in tue miaitnteir vessels.If a wlieal is produced by skin stimula- tioln, tlme site affected will not produce anotier wlieal u'ntil after tlie lapse of some days.For that perio(l it is refractory to the same or simailar stimuili.In refracto,'i- ne;;ss thie miniute vessels at e dilated, an(I (lo inot respond eitlier to vaso-constrictor substance or, on the otlier hand, to liistaminie or causes of increased p-ermeability.Lewis deicledl timat this is a dhirect property of tIme blood vessels.Aplparenftly the sallle plllenomlenon occur's ill the hlaemor- rhg.1ic diatlhesis.Osle'6 inl 1911, recorded as case in wliiclm a illlistal(l leaf was plaredI oni the epigastriium of a man on.ac"oulmlt of a sd(ieim p)ainl.In fact, this pain was the first * Delivered to the 8heffield Medico-Chirurgical Society.symnp)tom of the onset of acuite purpura hbaemlorrlhagica, and on the-inext day the puirpura appeared, and evenitually ha-emortlhages extended over the entire body, except the site which lhad been covered an(d stimulated bv the mustard leaf.In acase of mine, a miianilhad a pain in th6e knee, Whicllh he thought was lue to a strain, and for whlbich hie put on an elastic knee-cap.Purpura subsequently