Hemophagocytic syndrome

Hemophagocytic syndrome, also known as hemophagocytic lymphohistiocytosis, is a rare condition often associated with viral infections.

Hemophagocytic syndrome
Diagnosis in short
Micrograph showing phagocytosed RBCs in hemophagocytic syndrome. H&E stain.
LM	macrophages containing erythrocytes (red blood cells), leukocytes, platelets
Subtypes	primary, secondary
LM DDx	overlapping cells, emperipolesis
Molecular	FHL1 mutation or FHL2 mutation in primary form
Site	lymph nodes, liver, spleen, bone marrow, others
Associated Dx	only in secondary form (EBV infection, malignancy, rheumatologic disease)
Clinical history	+/-consanguinity for primary form (autosomal recessive)
Signs	fever, splenomegaly, jaundice
Prevalence	rare
Blood work	+/-EBV serology (secondary form), +/-HIV serology (secondary form)
Prognosis	dependent on underlying cause
Clin. DDx	malignancy
Treatment	dependent on underlying cause

Clinical

Features:

• Fever.
• Splenomegaly.
• Jaundice.

Involved organs:

• Lymph nodes.
• Liver.
• Spleen.
• Bone marrow.

Classification

Classified by etiology:

1. Primary, i.e. inherited:
   • Etiology: dysfunction of cytotoxic T lymphocytes with macrophage activating cytokines.
   • Autosomal recessive.
   • Two genes identified:
     • FHL1.
     • FHL2.
2. Secondary:
   • Infection, e.g. EBV (most common infectious etiology), HIV.
   • Malignancy.
   • Rheumatologic condition.

Microscopic

Features:

• Macrophages with phagocytosed:
  • Erythrocytes.
  • Leukocytes.
  • Platelets.

DDx:

• Overlapping cells (red blood cells overlapping macrophages).
• Emperipolesis in the context of other pathology.

Images

• 

  Hemophagocytic syndrome - cropped - very high mag. (WC)

• 

  Hemophagocytic syndrome - very high mag. (WC)

• 

  HLH (WC)

www:

• Hemophagocytic syndrome - several images (upmc.edu).

See also

• Hematopathology.
• Myospherulosis.
• Emperipolesis.