Pure red cell aplasia

normocytic, normochromic anemia characterized by a severe reduction in circulating reticulocytes and marked reduction or absence of erythroid precursors in the bone marrow

thought to be related to abnormal T-cell function and IgG antibodies that target erythroblasts and erythropoietin

• Acquired

  • Most often idiopathic

  • Possible associated conditions

    • Thymoma

    • Myelodysplastic syndrome

    • Adverse drugs effects (e.g., from phenytoin, chloramphenicol)

    • Parvovirus B19 infection

    • Autoimmune disorders (e.g., type 1 diabetes, thyroiditis, rheumatoid arthritis)

• Congenital: Diamond-Blackfan anemia (DBA)

• Low reticulocyte count

• Bone marrow biopsy shows marked reduction or absence of erythroid precursors.

• Treatment of the underlying cause (e.g., cessation of possible offending agents, thymectomy)

• Red blood cell transfusion for symptomatic patients

• Immunosuppressive and/or cytotoxic agents (e.g., glucocorticoids, cyclosporine, cyclophosphamide)

• Intrinsic defect of erythroid progenitor cells → ↑ apoptosis

• Usually autosomal dominant inheritance or associated with impaired ribosome synthesis mutations

• Rapid onset of macrocytic (nonmegaloblastic) anemia in infancy (usually diagnosed within the first year of life)

physical abnormalities manifest in ∼50% of affected individuals

• Fatigue, poor feeding

• Short stature, webbed neck

• Upper extremity malformations (e.g., triphalangeal thumbs)

• Microcephaly, micrognathia

• Hypertelorism, flat nasal bridge, cleft palate

• Congenital cataracts or glaucoma

• Atrial and ventricular septal defects

• Electrophoresis

  • Elevated HbF levels

  • Low total Hb levels

• Specific laboratory findings

  • Elevated erythrocyte adenosine deaminase levels (eADA)

  • Increased expression of i antigen in RBCs

• Corticosteroids (first-line treatment)

• Chronic red cell transfusions: individuals who do not respond to corticosteroids

• Hematopoietic stem cell transplantation

• Increased risk of malignancy: acute myelogenous leukemia, myelodysplastic syndrome, solid tumors (e.g., colon cancer, osteogenic sarcoma)

• Treatment-associated complications: iron overload due to repeated transfusions, corticosteroid-induced hyperglycemia

• Endocrine dysfunction: adrenal insufficiency, hypogonadism, vitamin D deficiency

X-ray right and left thumb (PA view)

A small triangular bone (delta phalanx, or longitudinal epiphyseal bracket; red overlay) is present between the proximal and distal phalanx of each thumb. There is ulnar deviation of the distal thumbs.

A delta phalanx can appear as an isolated finding or as part of a wide variety of congenital syndromes and dysplasias.