What is Histiocytosis X?

Histiocytosis X

Histiocytosis X, also known as Langerhans cell Histiocytosis (LCH) results from the neoplastic proliferation of Langerhans cells. Langerhans cells (LCs) are the specialized dendritic cell that resides in mucocutaneous tissue and upon activation become specialized for antigen presentation to T cells. Upon maturation, LCs looks more like that of tissue macrophage (morphologists call it histiocyte) that’s why it is known as LCH or Histiocytosis X. 

The peak age of onset is 2-4 years of age. Males are affected more than female.

Clinical features of histiocytosis X:

• It is a multi-system disorder but in up to 25% of cases, only one system may be affected too. 

• Skin: A skin rash is common. Individual histiocytomas are pinkish-brown papules of varying size (1-5 mm)

• Respiratory: Lung fibrosis, bullae and large airway obstruction by histiocytomas. Both restrictive and /or obstructive respiratory defects are found sometimes. 

• Bone: Any bone may be involved but it has a special predilection to the skull bones. There, it appears as a large radiolucent lesion on X-ray skull. Marrow infiltration may take place resulting in pancytopenia. 

• Ears: Otitis externa, aural discharge

• Eyes: Retro-ocular mass causes proptosis

• Reticuloendothelial system: Splenomegaly, hepatomegaly, lymphadenopathy. Sometimes, lymphadenopathy is massive

• CNS: In one-third of the cases, Diabetes insipidus may be developed due to histiocytic infiltration in the pituitary stack resulting in lack of ADH. Spinal cord compression may occur in rare cases. 

Variants of histiocytosis X:

Diagnosis of histiocytosis X: 

By demonstrating histiocytes and small round cells in histological specimens of affected tissues

Treatment of histiocytosis X: 

• Spontaneous regression (may occur in some cases)
• Steroids
• Cytotoxic drugs (e.g. vincristine or etoposide) in some cases

Reference: 

• Harrison’s Principles of Internal Medicine 2 volumes 19th Edition: 709
• Rapid Review Pathology, 4th Edition by EDWARD F. GOLJAN, MD: 344 or 350
• BRS Pathology, 5th Edition: 358
• Robbins basic pathology, 10th Edition: 484 (491)