Osteopetrosis

Osteopetrosis is a term that refers to a group of rare disorders of the skeletal system characterized by increased bone mass (density) as seen on X-ray images. Sometime referred to as Marble Bone Disease, osteopetrosis may be inherited and because of the high density, bone becomes brittle causing multiple bone fractures and in some cases, skeletal abnormalities.

ADO*, autosomal dominant osteopetrosis  occurs 1 in 20,000 births (0.005%) and is more prevalent than ARO*, autosomal recessive osteopetrosis, which occurs 1 in 250,000 births (0.0004%).

The root cause of osteopetrosis is failure of osteoclasts* (a special kind of bone modeling cells) function as a result of mutations in multiple genes human. The infantile form, the intermediate form and the adult form are three major types of osteopetrosis. The infantile form is severer than other forms. If left untreated it can diminish life expectancy of the infant due to bone marrow failure. Adult form is milder and the life expectancy is normal. The intermediate form is found in young children is less severe than the infantile form.

The symptoms of osteopetrosis is diverse, from infantile life threatening marrow failure to casual bone fractures in adults. Symptoms include pancytopenia (a over all reduction in various types of blood cell numbers), neuropathy (peripheral nervous system conditions). Trivial injuries may result in bone fractures due to hardening of the bone thus incidentally exposing adult form of osteopeterosis, which otherwise may have gone unnoticed.

Though there is no cure is available yet, in severe infantile forms, where bone marrow fails, hematopoietic stem cell transplantation is employed. The drug erythropoietin may help in alleviating anemia. Vitamin D might help with hypocalcimia.        

A German radiologist, Albers-Schönberg, first described it in 1904.

*ADO – Only one of the two genes to be defective for disease onset.

*ARO – Both genes to be defective for disease onset.

*osteoclasts – a bone resorbing type of cells work in balance with osteoblasts, a special kind of bone forming type of cells.

Contributor: Duraiswamy Navaneetham PhD.

Temple University School of Medicine

Philadelphia, PA, USA

December 2009