Autoimmune Hemolytic Anemia - Hematology

Snapshot
- A 57-year-old woman recently moved from Florida to Maine over the summer. She presents in November as a new patient, looking to establish a primary care relationship. She complains that ever since the temperature dropped, she develops painful, numb, blue fingers, and toes. They return back to normal once she warms up indoors. However, this happens every time her fingers and toes are cold. Her nose sometimes turns blue too. On closer questioning, a few weeks ago, she felt fatigued and had a “long cold,” with sore throat and swollen lymph nodes. She shows a photo of her lymph nodes at the time.

Introduction

Characteristics	Warm Agglutinin (IgG)	Cold Aglutinin (IgM)
Temperature at which antibodies are most reactive to RBC	Body temperature	Lower temperatures (<37°F)
Chronic vs acute	Chronic	Acute Complement-mediated
Associated conditions	SLE(most common) CLL Drugs (α-methyldopa and penicillin)	Mycoplasma pneumonia Infectious mononucleosis (EBV)
Epidemiology	AIHA (most common)	More common in women
Mnemonic	Warm weather isGGGreat	Cold weather is for ice cream, yuMMM

Evaluation

Characteristics	Warm Agglutinin (IgG)	Cold Aglutinin (IgM)
Direct Coombs test results	+ Direct Coombs test with anti-IgG Coombs reagent	+ Direct Coombs test (DAT) with anti-C3 Coombs reagent
Indirect Coombs test results	+ Indirect Coombs test (tests for IgG autoantibodies)	- Indirect Coombs test (tests for IgG autoantibodies, not performed with IgM antibodies)
Other tests	RBCs spontaneously agglutinate at room temperature	Most accurate test Cold agglutinin titer
Complement levels	Normal	↓ C3 and C4

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