An 82-year-old woman with severe transfusion-dependent macrocytic anemia for 1.5 years was assessed for myelodysplastic syndrome (MDS). She had no radiation, chemotherapy, alcohol or drug usage, lymphadenopathy, or hepatosplenomegaly. Hypothyroidism and vitamin B₁₂ and iron deficiency were ruled out. Her complete blood count showed the following: white blood cells, 5.5 × 10⁹/L; hemoglobin, 76 g/L; mean corpuscular volume, 98.2 fL; reticulocytes, 3 × 10⁹/L; platelets, 336 × 10⁹/L; and neutrophils, 4.09 × 10⁹/L. Blood smear was normal. Bone marrow (BM) aspirate illustrated normal megakaryopoeisis/granulopoiesis without dysplasia. Erythropoiesis was lacking with rare erythroprecursors (panel A; May-Grunwald-Giemsa stain, original magnification ×50). BM biopsy showed absence/markedly decreased erythropoiesis (panel B; hematoxylin and eosin stain, original magnification ×20) confirmed by E-cadherin/hemoglobin A staining. CD34/CD117/MPO/CD3/CD20/Parvo-B19 demonstrated no intrinsic marrow pathology. Flow cytometry demonstrated a mild reversed CD4/CD8 without clonality. T-cell receptor results were nonclonal. Karyotype analysis illustrated monosomy X in 10 out of 20 metaphases. Her history of several pregnancies rendered unrecognized Turner syndrome unlikely. This level of monosomy X (50%) is distinct from the sporadic low levels (<10%) routinely seen in peripheral blood lymphocytes. Monosomy X is reported in MDS/AML as a marker of clonal expansion in BM. Other congenital or secondary causes of pure red cell aplasia (PRCA) were ruled out. A diagnosis of myelodysplastic PRCA was suggested based on the clinical presentations/laboratory tests/BM/cytogenetics.

Myelodysplastic PRCA is an uncommon form of MDS and pathophysiologically distinct from the other types of PRCA.