Condition at the benign end of the spectrum of histiocytosis X associated with unifocal or multifocal granulomas containing Langerhans cells & eosinophils
Terminology
Histiocytosis X comprises a spectrum of disorders.
EG
most benign.
Hand-Schuller-Christian disease
exophthalmos, diabetes insipidus, & bone destruction
Letterer-Siwe syndrome
Most severe & potentially fatal
characterized by hepatosplenomegaly, lymphadenopathy, anaemia, acute infections & a downhill course
Epidemiology
First two decades of life
Slightly more common in males
Pathology
cell of origin is the Langerhans cell, a dendritic antigen presenting cell that is found all throughout the body, particularly in the skin & bones
Langerhans cell contains Birbeck granules, & has a nucleus with a deep cleft
Other cells found in the granulomas include eosinophils, PMNLs, giant cells, & mononuclear cells. The Langerhans cells are arranged in clusters.
Necrosis is very commonly seen
Grossly the lesion is soft, tan to reddish & occasionally greenish
Distribution
Skull, spine, pelvis & long bones, particularly the femur
Most commonly unifocal but may be multifocal – up to 50%
Has a preference for the skull & femur in children (sites of haematopoietic tissue) & the pelvis, ribs & skull in adults
Clinical
Commonest symptom is pain. The pain is often worse at night
May be accompanied by a palpable mass, fever & a limited range of motion
Skin lesions are often seen
Investigations
Laboratory
Rarely helpful. Occasional leukocytosis & elevated ESR. Usually no eosinophilia
Xray
XR typically shows lucent lesion sometimes with sclerosis.
lesion is typically in the medullary canal of the diaphysis of a long bone
It can occur in the epiphysis, however, & cross open growth plates
It may cause cortical destruction
It is the great mimicker & is in the differential diagnosis of any skeletal lesion. There may be expansion or periosteal reaction
In the spine causes vertebra plana
MRI
typically low T1 signal & high T2 signal. Surrounding oedema
Differential diagnosis
Osteomyelitis
Ewing’s sarcoma
Treatment
For EG, treatment is usually observation & the tendency is for resolution. Healing usually takes at least 5 months.
If there is ongoing pain or a lesion in a weight bearing bone then intralesional corticosteroids or curettage & bone grafting is used
