Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (295 page)

   Bone marrow aspiration and biopsy (see above).

   Cytogenetic and FISH analysis may establish the precise diagnosis in myelodysplastic syndromes or other hematologic malignancies. Newer whole-genome scanning technologies such as single nucleotide polymorphism (SNP) array–based karyotyping may be an additional diagnostic technology.

   Histochemistry for infiltrative congenital disorders.

Suggested Readings

Nester CM, Thomas CP. Atypical hemolytic uyremic syndrome: what it is, how is it diagnosed, and how is it treated.
Hematology Am Soc Hematol Educ Program.
2012;2012: 617–625.

Scheinberg P, Young NS. How I treat acquired aplastic anemia.
Blood.
2012;120:1185–1196.

PURE RED CELL APLASIA (PRCA)

   Definition

Chronic condition of profound anemia, characterized by severe reduction or absence of reticulocytes, and absent bone marrow erythroid precursors. (The congenital pure red cell aplasia is described below under Diamond-Blackfan anemia.) All other cell lines are normal. Most cases are mediated by IgG autoantibodies. PRCA may be associated with certain drugs, thymomas, collagen vascular syndromes, or CLL, or follow parvovirus B19 infection. It may also be part of the 5q
⁻
myelodysplastic syndrome. PRCA may also develop following administration of recombinant erythropoietin due to the development of antierythropoietin antibodies.

   Laboratory Findings

   CBC: severe reduction but normal-appearing RBCs; normal WBC and platelet counts.

   Reticulocytes are severely decreased or absent.

   Bone marrow is normocellular, but erythroid precursors cells are absent (giant normoblasts may be seen if the etiology is a parvovirus infection). White cell precursors and megakaryocytes (except in the 5q
⁻
syndrome) are normal.

   Serum iron and transferrin saturation are increased.

FANCONI ANEMIA (FA)

   Definition

The most common inherited AA. Autosomal recessive syndrome in childhood, associated with congenital anomalies of short stature, rudimentary thumbs, hypoplastic radii, renal anomalies, and skin spots. There is an increased incidence of myelodysplastic syndrome, acute myelogenous leukemia, and squamous cell carcinomas. The diagnosis is usually made between the ages of 6 and 9 years, but in rare cases, it may not been made until adulthood.

   Laboratory Findings

The hematologic findings evolve over months or years: macrocytic anemia, leukopenia due to neutropenia, and mild to moderate thrombocytopenia.

   
Cytogenetics
: Normal chromosome numbers but structural instability causing breaks, gaps, constrictions, and rearrangements. The diagnosis is made by the presence of increased chromosomal breakage in lymphocytes cultured in the presence of DNA cross-linking agents.