Abstract

BMJ 2014;348:g1721 doi: 10.1136/bmj.g1721 (Published 3 March 2014) Page 1 of 3 Practice PRACTICE RATIONAL TESTING 1 2 DawnBrassspecialtytraineeinhaematology ,PamMckayconsultanthaematologist ,FionaScott consultant haematologist 1 2 DepartmentofHaematologyNinewellsHospital,Dundee,UK; DepartmentofHaematology,BeatsonOncologyCentre,GartnavalGeneralHospital, Glasgow, UK; Department of Haematology, Western General Hospital, Edinburgh EH4 2XU, UK 1 2 This series of occasional articles provides an update on the best use frombothcommunity andhospitalisedpatients. Most ofkeydiagnostictestsintheinitialinvestigationofcommonorimportant lymphopeniasresultfromareductioninTcellnumbers.Chronic clinical presentations. The series advisers are Steve Atkin, professor, severelymphopenia (<0.5×10 /L) may predisposepatientsto head of department of academic endocrinology, diabetes, and opportunisticinfectionssuch as pneumocystis pneumonia, metabolism, Hull York Medical School; and Eric Kilpatrick, honorary professor,departmentofclinicalbiochemistry,HullRoyalInfirmary,Hull oesophageal candidiasis,herpes zoster,andsystemic York Medical School. To suggest a topic for this series, please email cytomegalovirus. us at [email protected]. Lymphopenia may beconsidered as primary or secondary. Primary causesareuncommon andincludeawiderangeof A 55yearoldman hadafull bloodcount undertaken when he primary immunodeficiency diseases.Thesediseasesare presentedwithfatigue.Therewasnosignificantmedicalhistory characterisedbyrecurrent,severeorunusualinfections,failure of note. He was anon-smokerwho tooknomedications. He 9 tothrive inchildren,andsometimesautoimmune and was noted tohavealymphopenia of 0.8×10 /L (reference 9 inflammatorycomplications.Lymphopeniaisafeatureofmany interval1.5-4.0×10 /L).Otherwisehisresultswerenormal,with butnotall of these disorders. Persistent lymphopenia isa haemoglobin of 135g/L (130-180 g/L), white cellcount 9 9 9 commonfeatureofseverecombinedimmunodeficiency,which 4.2×10 /L (4-12×10 /L), andplateletcount 150×10 /L 9 typically presentswithsevere,recurrent infectionsandfailure (140-400×10 /L).Hedidnotreturnforfollow-upbutpresented tothrive inthe firstyearof life andusually requiresstem cell toalocalhospitalemergencydepartmentsixmonthslaterwith transplantation.Thuspersistentlymphopeniainaninfantshould ashort historyof