LearningRadiology - Histiocytosis X

Histiocytosis X

Letterer-Siwe Disease
·       10% of histiocytosis X
·       Acute disseminated, fulminant form
·       Age at onset

o Several weeks after birth to 2 years

· Pathology

o May be confused with leukemia

· Symptoms

o Hemorrhage, purpura

o Severe anemia

o Fever

o Hepatosplenomegaly and lymphadenopathy

· Bone involvement in 50%

o Widespread lytic lesions

· Prognosis: 70% mortality rate

Hand-Schuller-Christian

· 15-40% of Histiocytosis X

· Triad of:

o Exopthalmus (33%)

o Diabetes insipidus (30-50%)

o Lytic skull lesions

· Pathology

o May simulate Ewing's sarcoma

· Age at onset

o 5-10 years

· Target organs

o      Bone
§       Lytic skull lesions with overlying soft tissue nodules
§       Large geographic skull lesions
§       "Floating teeth" with mandibular involvement

o      Soft tissue
§       Hepatosplenomegaly is rare
§       Lymphadenopathy which may be massive

o      Lung
§       Cyst and bleb formation with spontaneous PTX
§       Ill-defined diffuse nodular disease often leading to fibrosis and honeycombing

· Prognosis: spontaneous remissions and exacerbations

Eosinophilic granuloma

· 60-80% of Histiocytosis X

· Usually confined to bone

· Age at onset

o 5-10 years highest frequency

o Male predominance 3:2

· Location

o Calvarium>mandible>spine>ribs>long bones

o Most are monostotic (50-75%)

· Target organs

o      Skull (50%)
§       Diploic space of parietal bone most often
§       Round or ovoid punched out lesions with beveled edge
§       Sclerotic margin during healing phase
§       Beveled edge=hole-within-a-hole
§       Button sequestrum- bony sequestrum within lytic lesion
   §       Axial skeleton (25%)

o "Vertebra plana"-"coin-on-edge" (Calve disease)=collapse of vertebral body, mostly thoracic

§ Most common cause of vertebra plana in children

o      Proximal long bones (15%)
§       Expansile, lytic lesions, mostly diaphyseal
§       Soft tissue mass
§       Laminated periosteal reaction

o      Lung (20%)
§       Age peak between 20-40 years
§       Multiple small nodules
§       Predilection for apices
§       Prototype for honeycomb lung
§       Recurrent pneumothoraces (25%)
§       Rib lesions with fractures common

· Nuclear Medicine

o Negative bone scans in 35%

o Bone lesions usually not Ga-67 avid

o Ga-67 may be helpful in detecting non-osseous lesions

· Prognosis: excellent