Learning that someone you love has been diagnosed with SMO can be overwhelming. The information in this website may help you better understand the disease, but it is not intended to replace discussions with your healthcare provider.

What is Severe, Malignant Osteopetrosis (SMO)?

Osteopetrosis is a disease of the bones. It is NOT the common osteoporosis—that is a different condition. There are different forms of osteopetrosis, depending on how they are inherited and their characteristics. All forms of osteopetrosis have to do with an abnormal increase in the density of bones.1

Severe, malignant osteopetrosis is a form of osteopetrosis that is sometimes referred to as marble bone disease or malignant infantile osteopetrosis (MIOP) because it affects very young children. Severe, malignant osteopetrosis is a very severe form of osteopetrosis.1,2 While exact numbers are not known, it is thought that about 1 in 250,000 children are born with SMO.1

What happens in the body?

During normal bone development, existing bone material is constantly being replaced by new bone. Cells called osteoblasts cause new bone formation. Other cells called osteoclasts remove old bone through a process called resorption.1

In people with osteopetrosis, this balance is not maintained because their osteoclasts do not function properly. As a result, abnormal bone development occurs, which may cause many problems in the body, such as1,2:

  • Bone fractures
  • Problems with vision and hearing
  • Abnormal appearance of the face and head
  • Bleeding/blood disorders
  • Decreased ability to fight infection

Common characteristics

In SMO, the abnormal buildup of bone tends to narrow the space inside the bone. This means there is less space to make bone marrow, which is where new blood cells are formed. This can lead to2:

  • Anemia because of low red blood cells. Symptoms of anemia include pale skin and lack of energy
  • Bleeding problems because of low platelets. Platelets are blood cells needed for clotting to help stop bleeding
  • Many infections due to low white blood cells. White blood cells are needed to fight infections

There can also be a narrowing of the “tunnels” within bones of the skull (called foramina) through which the nerves for vision and hearing pass. When these nerves are squeezed by bones that overdevelop because of SMO, patients can develop problems with their vision and hearing.

Patients often suffer serious effects from SMO. These may include1,2:

  • Failure to thrive, slow growth in childhood
  • Impaired vision or blindness
  • Hearing loss
  • Abnormal head shape
  • Bone marrow failure, anemia
  • Frequent and recurrent infections
  • Frequent and recurrent bone fractures

SMO is associated with a lower life expectancy, with most untreated children dying within the first 10 years of life.1

References: 1. Stark Z, Savarirayan R. Osteopetrosis. Orphanet J Rare Dis. 2009;4:5. 2. Wilson CJ, Vellodi A. Autosomal recessive osteopetrosis: diagnosis, management, and outcome. Arch Dis Child. 2000;83(5):449-452.
Diagnosing SMO


Important Information About ACTIMMUNE

What is ACTIMMUNE® (Interferon gamma 1-b) used for?

ACTIMMUNE® (Interferon gamma 1-b) is part of a drug regimen used to treat Chronic Granulomatous Disease, or CGD. CGD is a genetic disorder, usually diagnosed in childhood, that affects some cells of the immune system and the body’s ability to fight infections effectively. CGD is often treated (though not cured) with antibiotics, antifungals, and ACTIMMUNE.

ACTIMMUNE is also used to slow the worsening of severe, malignant osteopetrosis (SMO). SMO is a genetic disorder that affects normal bone formation and is usually diagnosed in the first few months after birth.

When should I not take ACTIMMUNE?

Don’t use ACTIMMUNE if you are allergic to interferon-gamma, E coli-derived products, or any ingredients contained in the product.

What warnings should I know about ACTIMMUNE?

At high doses, ACTIMMUNE can cause (flu-like) symptoms, which may worsen some pre-existing heart conditions.

ACTIMMUNE may cause decreased mental status, walking disturbances, and dizziness, particularly at very high doses. These symptoms are usually reversible within a few days upon dose reduction or discontinuation of therapy.

Bone marrow function may be suppressed with ACTIMMUNE, and decreased production of cells important to the body may occur. This effect, which can be severe, is usually reversible when the drug is discontinued or the dose is reduced.

Taking ACTIMMUNE may cause reversible changes to your liver function, particularly in patients less than 1 year old. Your doctor should monitor your liver function every 3 months, and monthly in children under 1 year.

In rare cases, ACTIMMUNE can cause severe allergic reactions and/or rash. If you experience a serious reaction to ACTIMMUNE, discontinue it immediately and contact your doctor or seek medical help.

What should I tell my healthcare provider?

Be sure to tell your doctor about all the medications you are taking.

Tell your doctor if you:

  • are pregnant or plan to become pregnant or plan to nurse
  • have a cardiac condition such as irregular heartbeat, heart failure, or decreased blood flow to your heart
  • have a history of seizures or other neurologic disorders
  • have, or have had, reduced bone marrow function. Your doctor will monitor these cells with blood tests at the beginning of therapy and at 3-month intervals on ACTIMMUNE therapy
What are the side effects of ACTIMMUNE?

The most common side effects with ACTIMMUNE are “flu-like” symptoms such as fever, headache, chills, muscle pain, or fatigue, which may decrease in severity as treatment continues. Bedtime administration of ACTIMMUNE may help reduce some of these symptoms. Acetaminophen may be helpful in preventing fever and headache.

What other medications might interact with ACTIMMUNE?

Some drugs may interact with ACTIMMUNE to potentially increase the risk of damage to your heart or nervous system, such as certain chemotherapy drugs. Tell your doctor about all other medications you are taking.

Avoid taking ACTIMMUNE at the same time as a vaccination.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit www.fda.gov/medwatch, or call 1-800-FDA-1088. You may also contact the Horizon Pharma Medical Information Department toll-free at 1-866-479-6742 or medicalinformation

The risk information provided here is not comprehensive. To learn more, talk about ACTIMMUNE with your healthcare provider or pharmacist. The FDA-approved product labeling can be found at http://www.ACTIMMUNE.com or 1-866-479-6742.