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Case study (49) – Autoimmune hemolytic anemia

A 55-year-old lady, who is a heavy smoker, develops a productive cough and receives oral amoxicillin.

Her symptoms persisted, and one week later she developed progressive fatigue and shortness of breath.

Her full blood count shows:

Hemoglobin (Hb):  87 g/L

Mean corpuscular volume (MCV): 110 fL

White blood cells (WBC:) 11.3 X 109/L (neutrophils 71%)

Platelets: 305 X 109/L



Q1. Comment on the blood film.

. Comment on the blood film.

What is the likely diagnosis?

Q4. What further investigations are indicated?

Q5. How would you treat her?


A1. The chest x-ray shows evidence of lobar pneumonia affecting the right base.

A2. The blood film shows marked auto-agglutination, suggesting the presence of cold agglutinins.

A3. Autoimmune hemolytic anemia with cold agglutinins secondary to Mycoplasma pneumoniae infection.

A4. A direct anti-globulin (DAT) test was positive and demonstrated both IgM and complement on the red cell surface. Mycoplasma titers should be assessed.

The blood group should be determined, and the cold agglutinin titer should be measured.

Autoimmune hemolytic anemia following M. pneumoniae infection is typically associated with an increased titer of anti-I antibodies, which react optimally at 4°C.

Patients with cold reactive autoantibodies often develop acrocyanosis and Raynaud’s phenomenon, as the periphery is at a lower temperature than the body core. 

The suggested mechanism of autoimmune hemolytic anemia following M. pneumoniae infection is that antibodies to the organism cross-react with the I antigen, which is normally expressed on all adult red cells.

Other infections that may lead to autoimmune hemolytic anemia include syphilis and infectious

A5. Treatment is with erythromycin.