• tetrasomy 9p;
  • polycythaemia vera.

A 42-year-old Armenian woman was referred to the hospital for progressive left upper abdominal discomfort. The medical history revealed a non-erosive, seronegative rheumatoid arthritis for which she used non-steroidal anti-inflammatory drugs and sulphasalazine. The family history was non-contributory. Physical examination revealed no abnormalities except for splenomegaly. Laboratory investigations showed a leucocyte count of 23·8 × 109/l (normal: 4·0–10·0 × 109/l) with 88% neutrophils and no immature myeloid and erythroid cells, haemoglobin concentration of 12·8 g/dl (normal: 11·6–16·0 g/dl), mean corpuscular volume of 82 fl (normal: 80–101 fl), haematocrit of 0·39 l/l (normal: 0·37–0·47 l/l), platelet count of 508 × 109/l (normal: 150–300 × 109/l) and ferritin level of 7·2 μg/l (normal: 9–59 μg/l). A peripheral blood film showed teardrop cells. A biochemical profile was normal except for a slightly increased lactate dehydrogenase of 316 U/l (normal: 114–235 U/l). No signs of haemolysis were present. The vitamin B12 level was normal. The leucocyte alkaline phosphatase score was 230 (normal: 35–100) in the absence of reactive conditions. A bone marrow aspirate showed increased cellularity with prominent megakaryocytopoiesis and marked hyperploidy. Bone marrow histology showed panhyperplasia with prominent dysmegakaryocytopoiesis, intrasinusoidial haematopoiesis and diffuse reticuline fibrosis. In the absence of erythropoietin, spontaneous growth of erythroid progenitors could be shown in an erythroid burst-forming unit (BFU-E) assay. The red cell mass (RCM) was increased to 2500 ml. The mean normal RCM was calculated at 1525 ml according to the formulae of Pearson et al (1995), with an upper limit of 1906 ml (99% range which equates to ± 25% of the mean value). The bone marrow cells from a 24-h non-stimulated culture showed a 46,XX,add(15)(p13),add(21) (p13)[16]/46,XX[4] karyotype. Fluorescence in situ hybridization (FISH) demonstrated that the (extra) material on both the short arms of the chromosomes 15 and 21 was derived from chromosome 9. The full karyotype was therefore: 46,XX,add(15)(p13),add(21)(p13).ish der(15) t(9;15)(p13;p13)(wcp9+),der(21)(9;21)(p13;p13)(wcp9+). No constitutional cytogenetic abnormalities could be shown. No BCR–ABL transcripts were detected using reverse transcription polymerase chain reaction (RT-PCR). A chronic myeloproliferative syndrome was diagnosed which was compatible with polycythaemia vera (PV) with an unique chromosomal abnormality. Low-dose acetylsalicylic acid was started.

Recently, (partial) trisomy of the short arm of chromosome 9 and an additional i(9)(p10) as the sole anomaly in PV leading to tetrasomy of the short arm of chromosome 9 have been reported (Blij-Philipsen et al, 1997; Chen et al, 1998). In our case, a partial tetrasomy of the short arm of chromosome 9 was found, namely tetrasomy 9p13[RIGHTWARDS ARROW]pter. From these data it might be concluded that the amplification of a gene or genes on 9p (between p13 and pter) may play a crucial role in the pathogenesis of PV. This is supported by data showing that trisomy 9 is one of the most common anomalies in PV (Diez-Martin et al, 1991). To this end, understanding the role of human interleukin 11 (IL-11) receptor α-chain (IL11RA) gene (9p13) in PV might be of interest as IL-11 is thought to play a pivotal role in early haematopoiesis and at multiple stages of erythropoiesis (Quesniaux et al, 1992; Roeder et al, 1998).


  1. Top of page
  2. References