Pelger-Huet Anomaly in Cats

Transcription

1 Vet. Pathol. 22: 7-74 ( 98) Pelger-Huet Anomaly in Cats K. S. LATIMER, P. M. RAKICH, and D. F. THOMPSON Department of Veterinary Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA, and Animal Hospital of North Asheville, Inc., Asheville, NC Abstract. Pelger-Huet anomaly was diagnosed in a young male cat on the basis of persistent nuclear hyposegmentation of blood granulocytes, absence of clinical disease or feline leukemia virus infection, and demonstration of genetic transmission of the anomaly. Neutrophils, eosinophils, basophils, and monocytes had significantly less nuclear segmentation when compared to similar leukocyte types from a control cat. On smears of bone marrow, megakaryocytes also appeared hyposegmented. A test mating with an unaffected queen produced a litter of five kittens (three males, two females). One male and one female kitten had the Pelger-Huet trait on examination of blood smears. Autosomal dominant transmission of this anomaly is suspected based on these findings. Pelger-Huet anomaly is an inherited disorder of leukocyte development characterized by nuclear hyposegmentation of granulocytes.2 Although the nuclear shape of affected granulocytes resembles bands, metamyelocytes, or myelocytes, the chromatin pattern appears aggregated and mat~re.~ Peiger-Huet anomaly is considered a rare disorder and has been reported sporadically in people,' rabbits,' I and dogs.2..h.8.'2.. I A single report of Pelger-Huet anomaly in cats describes the hematologic findings in two ten-year-old castrated male littermates.2' The present report describes another case of Pelger-Huet anomaly in a male cat and the results of a test mating with an unaffected queen. Case History A five- to six-month-old male domestic shorthair cat was presented because of anorexia. The rectal temperature was 4.9"C, but no additional abnormalities were found on physical examination. A blood sample was collected in ethylenediaminetetraacetate for a complete blood count at a commercial laboratory (Roche Biomedical Laboratories, Inc., Burlington, NC) and feline leukemia virus test (Leukassay F, Pittman-Moore, Inc., Washington Crossing, NJ). Antibiotic therapy with amoxicillin and gentamicin sulfate was begun pending laboratory results. Examination of the stained blood smear revealed a left shift back to neutrophil metamyelocytes (table I) and the presence of eosinophil bands. However, these granulocytes had coarse, mature chromatin. On the basis of granulocyte nuclear morphology, Pelger-Huet anomaly was suspected. The test for feline leukemia virus was negative. At 2 weeks after treatment, the cat was clinically healthy. Evaluation of a second blood sample indicated persistent 7 hyposegmentation of granulocytes (table I). The owners temporarily donated the cat to the University of Georgia Department of Veterinary Pathology for additional hematologic and breeding studies. Materials and Methods Ethylenediaminetetraacetate-blood samples were collected periodically by jugular venipuncture for complete blood counts. White cell counts were done on an electronic particle counter (Coulter Counter, Model D2N, Coulter Industries, Inc., Hialeah, FL), and differential counts were done on Wright-stained blood smears.i A bone marrow aspirate was taken from the left trochantenc fossa using a disposable sternal needle. Feline leukemia virus testing was done on plasma samples by an enzyme-linked immunosorbent assay using a commercial kit as previously mentioned. Stained blood smears from the Pelger-Huet cat and a healthy control cat were compared to determine the degree of nuclear segmentation for neutrophils. eosinophils, basophils, and monocytes. One hundred consecutive cells of each leukocyte type were graded according to published guidelines.' The cells were scored as follows: grade, nucleus round or oval; grade 2, nucleus indented slightly; grade, nucleus bandshaped; grade 4, two lobes; grade, three lobes; grade, four lobes; grade 7, five lobes; grade 8, six lobes; grade 9, seven lobes. The data were tested by one way analysis of variance for each cell type. Group means were compared using Newman-Kuel's test. In each instance, the level of significance tested was P.. To determine the genetic transmittance of Pelger-Huet anomaly in cats, the male was mated to an unaffected, feline leukemia virus-negative queen. The offspring were surveyed for the Pelger-Huet trait at six weeks of age by microscopic examination of stained blood smears obtained from clipped toenails.

2 Pelger-Huet Anomaly 7 Table I. Sequential leukograms and feline leukemia virus test results for a cat with Pelger-Hiiet anomaly 9//8 I O/ 4/8 2/8 /4/84 7/9/84 Leu kocytes/pl, 2,, 7,28,89 Neutrophils/pl Segmented cells,44 Bands,,7,84,2 4,2 Juveniles Ly mphocytes/pl,99, 7,72,,4 Monocytes/pl Eosinophils/pl 9,4 4 Basophils/pl 4 8 Feline leukemia Negative ND Negative Negative Negative virus test ND = not determined. Results Periodic blood examinations over a ten-month period showed a persistent left shift in the absence of clinical disease or feline leukemia virus infection (table I). A shift to neutrophil metamyelocytes and myelocytes was observed, but the chromatin pattern remained coarse and mature. The majority of the neutrophils had band-shaped nuclei (fig. ). Most eosinophils had oval to indented nuclei (fig. 2). Occasionally, neutrophils and eosinophils had two rounded nuclear lobes connected by a thin filament, the so-called pince-nez or spectacle form. Basophils usually had band-shaped or bilobate nuclei (fig. ). Although basophils were filled with round grayish-beige granules, some of these cells had scattered, poorly defined metachromatic spots. Monocytes had round to slightly indented nuclei with a lacy chromatin pattern and blue-gray cytoplasm. Monocytes often were round and pseudopodia were inapparent (fig. 4). The morphology of lymphocytes, erythrocytes, and platelets was unremarkable. When compared to corresponding leukocyte types from a healthy control cat, the nuclei of feline Pelger- Huet neutrophils, eosinophils, basophils, and monocytes were significantly hyposegmented (P I., table ). As expected, monocytes had the least nuclear segmentation in both the Pelger-Huet and control cats. Basophils, on the other hand, had the most nuclear segmentation in the cat with Pelger-Huet anomaly. Besides granulocyte hyposegmentation, megakaryocytes in bone marrow aspirates had an apparent decrease in nuclear lobulation. A single test mating produced a litter of five healthy kittens (three males, two females). Blood smear examination indicated that one male and one female kitten had the Pelger-Huet trait (fig. ). No Barr bodies or sex chromatin drumsticks were observed in neutrophils or eosinophils from the affected female kitten. Discussion Three criteria are necessary to establish a diagnosis of Pelger-Huet anomaly.2 First, persistent hyposegmentation of granulocytes should be apparent on the blood smear. Second, infectious diseases, neoplastic diseases, or drug exposure which would result in acquired cellular hyposegmentation (pseudo-pelger-huet anomaly) must be excluded. Finally, an hereditary background or documented transmission of the Pelger- Huet trait should be established. Leukocyte nuclear hyposegmentation was present in this cat over a ten-month observation period. Detailed examination of the leukocytes on blood smears of this cat indicated significant nuclear hyposegmentation of neutrophils, eosinophils, basophils, and monocytes. Although Pelger-Huet anomaly is readily appreciated in neutrophils and eosinophils, nuclear hyposegmentation also has been reported in human ba~ophils.. ~ and in canine2 and humani4 monocytes. In studies of canine Pelger-Huet anomaly, some monocytes contained nuclei with little or no indentation instead of the more common horseshoe-shaped nucleus.2 Our findings are consistent with current theories of hematopoiesis which suggest that granulocytes and monocytes are derived from a common stem cell. Basophils are thought to develop in concert with other granulocytes in the bone marrow, but their stem cell has not been identified. Hyposegmentation of basophils in this cat provides indirect evidence that basophil development is closely related to the other lobated leukocytes. The apparent decrease in nuclear lobulation of megakaryocytes observed in this cat also has been described in persons7 which further supports current theories of hematopoiesis. These findings suggest that Pelger-Huet anomaly is a stem cell defect in the nuclear segmentation or lobulation process. Pseudo-Pelger-Huet anomaly is an acquired, usually

3 2 Latimer, Rakich, and Thompson Fig. : Fig. 2: Fig. : Fig. 4: Feline Pelger-Huet neutrophils; nuclear hyposegmentation with coarse mature chromatin. Feline Pelger-Huet eosinophils with rod-shaped granules and hyposegmented nuclei with coarse chromatin pattern. Feline Pelger-Huet basophils. More nuclear segmentation is apparent than in other leukocyte types. Feline Pelger-Huet monocyte with round cell margins lacks pseudopodia. Lymphocyte is present for size comparison. Table. Nuclear segmentation grades for consecutive leukocytes of various types Leukocyte twe Neutrophils Pelger-Huet" Monocytes Pelger-Hueta Eosinophils Pelger-Huet" Basophils Peker-Huet' a 2 Nuclear segmentation grade Average segmentation grade Significantly different from control at P c..

4 Pelger-Huet Anomaly 7 transient. hyposegmentation of granulocytes. This entity can occur in people during severe infection, leukemia, neoplasia metastatic to the bone marrow, and following drug therapy with sulfonamides or colchicine." In veterinary medicine, psuedo-pelger-huet anomaly has been reported in a cow with ruminal atony4 and in a dog following treatment with multiple drugs. I' Although pseudo-pelger-huet anomaly has not been described in cats, feline leukemia virus infection can cause normal to low white blood cell counts with prolonged left shifts.i States of acquired granulocyte hyposegmentation tend to be transient if the underlying disease is corrected. Pseudo-Pelger-Huet anomaly was excluded in this cat on the basis of negative feline leukemia virus tests, absence of clinical disease, and persistence of leukocyte nuclear hyposegmentation. Conclusive proof of a diagnosis of Pelger-Huet anomaly was provided by breeding studies. In a single test mating, two of five kittens had the Pelger-Huet trait (fig. ). Since one of the affected kittens was a female and the other a male, this breeding trial demonstrates autosomal transmission of the anomaly. This finding agrees with previous studies of Pelger-Huet transmission in rabbits,'' persons," and dogs.2 The number of affected to unaffected kittens approximates a : ratio. Assuming Pelger-Huet anomaly is controlled by a single allele, two possible explanations exist. First, the male parent could be homozygous and the female parent heterozygous for a recessive Pelger- Huet gene. Upon mating these animals, % of the kittens would be homozygotes and express the Pelger- Huet trait. Based on current evidence this situation is unlikely. The homozygous state is usually lethal in rabbits' I and possibly in persons.' Surviving homozygous rabbits'' and persons'.7 are rare and have variable degrees of skeletal deformity. The scarcity of Pelger- Huet anomaly in cats suggests the female was negative for the Pelger-Huet gene unless spontaneous mutation occurred. IrQ Fig. : Genetic transmission of Pelger-Huet anomaly in cats. Squares represent males and circles represent females. Black symbols indicate affected animals. The second plausible explanation is that the male could be heterozygous for a dominant Pelger-Huet gene while the female was negative for this trait. If these animals were mated, % of the kittens would be heterozygous for a dominant gene and express the Pelger-Huet trait. Genetic studies in rabbits' and persons.', l9 support this hypothesis, but further breeding studies will be necessary to prove this theory in cats. Although rare, the incidence of Pelger-Huet anomaly in cats may be higher than reflected in the literature because complete blood counts are not done routinely on healthy animals, and the condition may be diagnosed improperly when encountered. When a persistent left shift is reflected in hemograms, Pelger-Huet anomaly often is not considered in the differential diagnosis, whereas severe bacterial infection and preleukemic syndromes are. Acknowledgements Presented in part at the Thirty-Fifth Annual Meeting of the American College of Veterinary Pathologists and the Annual Meeting of the American Society of Veterinary Clinical Pathologists, Toronto, Ontario, Canada, November, 984. We thank Ms. Dawn Martin for donating her cat for study, Ms. Lou Ann Brown for providing the female cat, and Ms. Ingrid Kircher for technical assistance. This research was supported by the Department of Vetennary Pathology and the University of Georgia Veterinary Medical Experiment Station. References AZNAR, J.; VAYA, A,: Homozygous form of the Pelger- Huet leukocyte anomaly in man. Acta Haematol (Basel) : 9-2, 98 BOWLES, C.A.: ALSAKER, R.D.; WOLFLE, T.L.: Studies of the Pelger-Huet anomaly in foxhounds. Am J Pathol 9:27-248, 979 BREITSCHWERDT, E.B.; OCHOA, R.; BARTA, M.: BARTA,.; MCCLURE, J.; WALTMAN, C.: Clinical and laboratory characterization of Basenjis with immunoproliferative small intestinal disease. Am J Vet Res , 984 CARPER, H.A.; OEHLER, P.: Pseudo-pelger neutrophils in the cow. VM/SAC : , 9 FELDMAN, B.F.: Pelger-Huet anomaly. In: Spontaneous Animal Models of Human Diseases, ed. Andrews, Ward, and Altman, pp Academic Press Inc., New York, 979 FELDMAN, B.F.: RAMANS, A.U.: The Pelger-Huet anomaly of granulocytic leukocytes in the dog. Canine Pract :22-, 97 HAVERKAMP BEGEMANN, N.; VAN LOOKEREN CAMPAGNE, A.: Homozygous form of Pelger-Huet nuclear anomaly in man. Acta Haematol (Basel) 7:29-, 92

5 74 Latimer, Rakich, and Thompson 8 KISS, M.; KOMAR, G.: Pelger-Huet sche Kernanomalie der Leukozyten bei einem Hunde. Berl Muench Tieraerztl Wochenschr 24:474-47, 97 9 KLEIN, A.; HUSSAR, A.E.; BORNSTEIN, S.: Pelger-Huet anomaly ofthe leukocytes. N Engl J Med 2: 7-2, 9 LASZLO, J.; RUNDLES, R.W.: Morphology of granulocytes and their precursors. In: Hematology, ed. Williams, Beutler, Erslev, Rundles, 2nd ed., pp McGraw- Hill Book Co., New York, 977 NACHTSHEIM, H.: The Pelger-anomaly in man and rabbit: A Mendelian character of the nuclei of the leucocytes. J Hered 4: -7, 9 2 PACE, E.M.: Pelger-Huet anomaly transmission. Canine Pract 4: -4, 977 PRASE, K.W.: Disorders of leukocytes. In: Textbook of Internal Medicine, Diseases of the Dog and Cat, ed. Ettinger, 2nd ed., pp W.B. Saunders Co., Philadelphia, 98 4 ROSE, W.F.; GURNEY, C.W.: The Pelger-Huet anomaly in three families and its use in determining the disappear- ance of transfused neutrophils from peripheral blood. Blood 4: 7-8, I99 SCHALM, O.W.: Interesting features of canine leukocytes. Calif Vet 9:2-27, 9 SCHALM, O.W.; JAIN, N.C.; CARROLL, E.J.: Veterinary Hematology, rd ed., pp. -8. Lea & Febiger, Philadelphia, 97 7 SCHRADER, J.W.: Bone marrow differentiation in vitro. CRC Crit Rev Immunol4: , SHULL, R.M.; POWELL, D.: Acquired hyposegmentation of granulocytes (Pseudo-Pelger-Huet anomaly) in a dog. Cornell Vet 9:24-247, SKENDZEL, L.P.; HOFFMAN, G.C.: The Pelger anomaly of leukocytes: Forty-one cases in seven families. Am J Clin Pathol7:294-, 92 2 TVEDTEN, H. W.: Pelger-Huet anomaly, hereditary hyposegmentation of granulocytes. Comp Pathol Bull : -4, 98 2 WEBER, S.E.; FELDMAN, B.F.; EVANS, D.A.: Pelger-Huet anomaly of granulocytic leukocytes in two feline littermates. Feline Pract :44-47, 98 Request reprints from Dr. Kenneth S. Latimer, Department of Veterinary Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 2 (USA).