Remarks on THE HAEMORRHAGIC DIATHESIS
Authors: H. L. Tidy
Journal: BMJ (1928)

THE title " The haemorrhagic diathesis" includes all varieties of primary purpura.. Secondary symliptomatic purpura will be r-eferred to incidentally.Haemophilia is not included.The primary .purpurasare divided into two groups:(1) haemorrhagic purpura; (2) anaphylactoid purpuira .The first group includes all grad.es of severity in which the escape of whole blood from the vessels constitutes the essential feature.The anaphylactoid group includes Henoch's anid Sch6nlein's purpura.This group exhibits not only haemorrhages, but also swellings which do niot contain blood cells, and is characterized by abdomiiinal pain and colic, and by swelling and pain around the joints.In urticaria there are similar swellings and pains, but no escape of blood.lJrticaria is undoubtedlv due to a transient increased permeability of the capillary endo- theliium.It will be held here that three grades of capillary defect exist-namely, haemorrhagic purpura, anaphylactoid purpura, and urticaria.Variations in the platelets are secondary factors.The term a angio-staxis" is suggested for the group.Normal Function of the Platelets.Two funcietions are usually ascribed to the platelets.(1) When lplatelets disintegrate they are said to seE free substances which take part in coagulation of the blood.It is doubtful whether the action of coagulation is of great imiiportance.(2) A function in protecting injured or abnormally permeable capillary endothelium.This is effected by platelets adhering in masses to injured intima, and is partly a mechanical blockage and-partlyv a preparaton for coagulation of the blood.-In capillary haemorrhages the-circulating.platelets are thus affected by (a) a loss eqial, to the -amoit of blood escaping, and (b) a special loss owilng -to their" adherence to the weakened spots and consequelnt destruction, -;and lhence the loss of platelets is out -of p)roliortionto the amount of blood escaping.Tbe llormal number of platelets is from 200,000 to 350,000 per c.mm.It may vary with great rapidity.-.SYMPTOMATOLOGY OF THE HIArMO-RRHAGIC PURPUIJ \t.The principial miianlifestations to be considered are:1.The character of the haemorrbages. 2. Coagulation time, and retractility of the clot.3. Bleeding time.4. The toturniquet or capillary resistance test (the Rumpel-Leede test).Hess's test. 5. Variations in the number of the platelets.6.The presence or absence of splenic enlargement.1.The Character of the Haenmorrhaaes.T'le haemorrhages may be inito the skiil, frlom tlhe mulllcous membranes, into the subQutan.eoustissues consti- tutinlg ecchymoses, anid also a general tenidency to bleed easily.T he relationship of suclh conditions as essential haematuiria is very importantl, but will not be lhere referred to further.Many enitities lhave been separated from these haemiior- rhages, such as purpura simplex, lplrpura htaemllorrlragica, and many others.Bleeding from the mlucous memiibranes can1not be accelpted as distinguishing a slpecial group of plrlpura.It ofteni occur s froin timne to tine, to a mild degree, in cases which nlever exhibit any giucat severity.N-eitlher by t he type of haemr'liages, noilr by tlheir severity can any dividing line be distinguIlished between tlhe puirpuras * Abstract of 'paper.readbefore the Seliion of Medieino of thie Royal Society of Mledicine on February 28th, 1928. in this group.If purpura haemorrhagica is to be separated as an entitv from mild chronic purpura it must be on other than the clinical manifestations.