Malignant infantile osteopetrosis is a rare disease but can be clinica
lly unequivocally diagnosed. Normal bone formation in the presence of
decreased bone breakdown leads to the typical symptoms. The only prove
n curative approach, bone marrow transplantation, can reverse most of
the symptoms and prevent progression to irreversible nerve damage when
done early in infancy. Therefore, early diagnosis is decisive. We pre
sent a case report of an infant with osteopetrosis and discuss pathoge
nesis and therapeutical options.