Langerhans Cell Histiocytosis (LCH)

1

What are the former names of Langerhans cell histiocytosis?

What is known today as Langerhans cell histiocytosis (LCH) was first described in the early 1900s. By 1953, the diagnoses of eosinophilic granuloma, Hand-Schüller-Christian disease, Letterer-Siwe disease, and Hashimoto-Pritzker disease were grouped together as a disease spectrum known as Histiocytosis X. The “X” stood for “unknown,” representing the lack of understanding of the underlying pathology. In 1973 Nezelof and colleagues coined the term LCH with the identification of Birbeck granules, thought to be pathognomonic of Langerhans cells, which until recently, was considered the pathogenic cell.

2

What is the cause of LCH?

The underlying etiology has long been debated: dysfunctional or exaggerated inflammatory response versus neoplastic disorder. It has since been determined that LCH is secondary to a clonal expansion or neoplasm of myeloid precursor cells that differentiate into dendritic cells.

3

Discuss the clinical presentations of LCH.

Patients may present with a wide spectrum of disease involving one organ system (single-system) or more than one (multisystem).

• Single-system: The most common presentations include bone or skin lesions.

  • Lytic bone lesions typically involve the skull, followed by the spine, limbs, or pelvis.

  • Skin involvement is noted in approximately one-third of children with LCH, classically an erythematous papule that may ulcerate or depigment.

  • Lymph node involvement occurs in less than 10% of children.

• Multisystem: Other organ systems that can be involved include the liver, spleen, bone marrow, lungs, and central nervous system (CNS). The aggressive presentation of multisystem disease is usually seen in children younger than 2 years. The presentation is often similar to an acute leukemia, with evidence of bone marrow suppression, hepatosplenomegaly, and constitutional symptoms.

  • Lungs: Involvement may be manifested by respiratory distress with tachypnea, retractions, and persistent cough. Chronic respiratory failure may ensue as a result of widespread cyst and bullae formation. Rupture of a bullous lesion may lead to pneumothorax.

  • Bone, skin, and lymph node involvement usually coexist with a presentation similar to single-system disease.

  • Gingival disease is marked by early loss of deciduous teeth and gum hypertrophy.

  • Auditory canal involvement is manifested by persistent ear drainage nonresponsive to antibiotics.

4

Describe the epidemiology of LCH.

LCH occurs in approximately 5 out of 1,000,000 children, with an average age of diagnosis of 3 years. Males and females are affected near equally, and Hispanic children are more commonly affected than other ethnicities.