Cold AIHA

Question 1

What is cold AIHA and how does it arise?

Answer 1

• Autoimmune haemolysis of RBCs at cold temperatures.
• Production of IgM antibodies which bind to RBCs optimally at 4 degrees.
• Idiopathic or due to an underlying condition, such as cancer.
• The IgM antibodies bind to the RBCs in the peripheral circulation as it is cooler here, and this activates complement which creates pores in the RBCs and leads to intravascular lysis of the RBCs.
• This is a form of intravascular haemolysis.

Question 2

What are the symptoms and their explanations?

Answer 2

• Anaemia, fatigue, breathlessness – haemolysis of RBCs.
• Splenomegaly – increased RES mediated haemolysis.
• Jaundice – increased production of bilirubin due to breakdown of RBCs.
• Raynaud’s Phenomenon – painful blue fingers and occlusion of the vessels). Due to haemolysis of RBCs at the peripheral areas of the body.
• These symptoms are all seen when the patient enters a colder area.

Question 3

What are the laboratory findings?

Answer 3

• Anaemia – low RBCs and Hb
• Increased reticulocytes
• Blood film – agglutination at room temperature

Question 4

What further tests should be carried out?

Answer 4

• Strong positive DAT at room temperature, and shows only complement binding to the RBCs – no Ig involvement in binding.
• Cold agglutinins looked for in the sample.
• Biochemistry tests: LDH (increased), bilirubin (increased), haptoglobin (decreased)

Question 5

How is cold AIHA treated?

Answer 5

• Keep warm and wrap up in the cold, avoid the cold
• Monoclonal antibodies e.g., rituximab to remove self-reactive B lymphocytes
• Treat the underlying condition
• Folic acid and transfusions in severe cases