Case report and literature review: transient Inab phenotype and an agglutinating anti-IFC in a patient with a gastrointestinal problem.
BACKGROUND
The Inab phenotype is a rare deficiency of all Cromer antigens. These antigens are carried on the decay-accelerating factor (DAF, CD55) molecule that is attached to the red blood cell (RBC) membrane by a glycosylphosphatidylinositol (GPI) anchor. Although typically inherited, an acquired and transient form of the Inab phenotype also exists. A patient with the triad of transient Inab phenotype, a direct-agglutinating anti-IFC, and gastrointestinal (GI) abnormalities is reported.


METHODS
An 18-month-old boy with gastroesophageal reflux disease requiring a feeding tube, milk and soy intolerance, and severe growth retardation, as well as vision and hearing deficits from cytomegalovirus infection, was identified when pretransfusion testing revealed a potent panagglutinin (titer > 2000 at 4 degrees C). This antibody did not react with Dr(a-) and IFC RBCs, and the autocontrol was negative. The patient's RBCs lacked CD55 by flow cytometric techniques but had normal levels of CD59 and antigens such as Yt(a) and Emm, carried on GPI-linked proteins, thus excluding paroxysmal nocturnal hemoglobinuria. Several months after initial detection, the anti-IFC was virtually undetectable and his cells reacted weakly with anti-IFC, anti-Dr(a), and anti-CD55. RBCs from the propositus' parents and brother demonstrated normal CD55 and CD59 expression.


CONCLUSIONS
This is the first example of a direct-agglutinating anti-IFC. The cause of the transient depression in CD55 protein (and thus Cromer system antigens) and appearance of anti-IFC remains unknown, as does the relationship between the patient's GI system abnormalities and these serologic findings.
Yazer
Mark H
MH
Institute for Transfusion Medicine and Department of Pathology, University of Pittsburgh, Pennsylvania, USA.
Judd
W John
WJ
Davenport
Robertson D
RD
Dake
Louann R
LR
Lomas-Francis
Christine
C
Hue-Roye
Kim
K
Powell
Vivien
V
Reid
Marion
M
D000371:Agglutination; D018958:CD55 Antigens / Q000097:blood*; D018957:CD59 Antigens / Q000097:blood*; D004910:Erythrocyte Membrane / Q000276:immunology; D005500:Follow-Up Studies; D005764:Gastroesophageal Reflux; D006801:Humans; D007223:Infant; D007518:Isoantibodies / Q000097:blood* / Q000276:immunology; D008297:Male; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D012196:Review Literature as Topic; D017422:Sequence Analysis, DNA; D013997:Time Factors; D044465:White People
D018958:CD55 Antigens; D018957:CD59 Antigens; D007518:Isoantibodies