Discussion: Osteopetrosis:
Cause:
- defect in osteoclasts
- osteoclasts helps in remodeling bone (allows growth and maturation of bone) as well as modeling bone (expansion of marrow cavity)
- incidence unknown but thought to be 1/100,000 - 500.000
Types:
- infantile : Autosomal Recessive. Characterized by severe marrow failure and death within first decade if untreated.
- adult onset: Autosomal Dominant. prognosis is better. Usually no evidence of marrow failure.
- intermediate (childhood): poor prognosis, but no manifestations of marrow failure.
Clinical Presentation:
- Infantile:
- pancytopenia
- cranial nerve entrapment from failure of foramina in skull to widen. leads to deafness, proptosis etc. hydrocephalus also common.
- fragile bones despite sclerosis --> fractures common.
- extramedullary hematopoiesis --> HSM, hemolysis.
Radiologic findings:
- diffuse sclerosis
- osteopathia striatum in iliac wings or end of long bones
- under tubulization (Ehrlen Meyer Flask)
- bone-in-bone appearance
Diagnosis:
- usually based on radiographic findings alone. biopsy not necessary.
Treatment:
- based on trying to activate dormant osteoclasts: Calcitrol. Has only modest improvement
- gamma interferon: increases bone marrow volume. Better long term benefits.
- EPO for anemia
- BMT is the only definitive treatment. 
