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
Site	lymph nodes, liver, spleen, bone marrow, others
Associated Dx	only in secondary (EBV infection, malignancy, rheumatologic disease)
Signs	fever, splenomegaly, jaundice
Prevalence	rare
Prognosis	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.