Systemic Symptoms and Physical Features

While the most critical aspects of Mulibrey nanism are growth and heart health, the condition is “multisystemic,” meaning it can affect many different parts of your child’s body ^[1][2]. Understanding these physical features can help you and your medical team monitor your child’s health more comprehensively.

Distinctive Facial and Skeletal Features

Many children with Mulibrey nanism share a similar “look.” These features are caused by the way the TRIM37 gene affects the development of bone and cartilage ^[3][4].

• Facial Appearance: Common features include a triangular-shaped face, a prominent or bulging forehead, and a low bridge of the nose ^[5][6]. Your child may also have a high-pitched, sometimes “squeaky” voice ^[5].
• Bone Structure: The long bones (like those in the arms and legs) are often slender and may have a slight bow ^[2]. Inside the bone, the walls (cortex) may be unusually thick while the center (medullary cavity) is narrow ^[2].
• Spine and Sella Turcica: The bones of the spine (vertebrae) may appear taller than average on an X-ray ^[2]. Additionally, a specific structure at the base of the brain called the sella turcica—which holds the pituitary gland—often has a distinctive “J-shape” in children with this condition ^[5].
• Fracture Risk and Activity: Because of these structural differences, about half of children with Mulibrey nanism may experience bone fractures or develop fibrous dysplasia (a condition where normal bone is replaced by fibrous tissue) ^[2]. Due to this fracture risk and underlying heart considerations, you will need to discuss safe levels of physical activity, recess, and sports with your medical team. Children are encouraged to stay active, but certain high-impact activities may need to be avoided.

The Eyes and Brain

Two very specific signs can help doctors confirm a diagnosis of Mulibrey nanism during a physical exam:

• Yellowish Eye Spots: During a dilated eye exam, an ophthalmologist may see small, yellowish-white dots in the fundus (the back of the eye) ^[5][7]. These spots do not usually affect vision, but they are a hallmark sign of the condition ^[5].
• Brain Variations: Besides the J-shaped sella turcica, some children may have slightly enlarged ventricles (the fluid-filled spaces in the brain) ^[5][8]. As mentioned, these structural differences do not typically impact cognitive intelligence.

Internal Organ Involvement

The “LI” in the Mulibrey acronym stands for the liver, but other organs are involved as well:

• Liver (Hepatopathy): The liver can become enlarged (hepatomegaly) and may develop scarring (fibrosis) or fatty changes ^[9][10]. Monitoring liver health is vital, as it is one of the major factors in a child’s long-term outlook ^[9][7].
• Kidneys: While kidney function is usually normal, some children may develop small cysts or have an increased risk of Wilms tumor, a rare kidney cancer that is highly treatable if caught early through regular ultrasounds ^[11][12].

The Immune System and Infections

Recent research has shown that the TRIM37 gene also plays a role in how the body fights off germs ^[1][13].

• Frequent Infections: Many children with Mulibrey nanism experience recurrent respiratory infections, such as pneumonia or severe colds ^[1][13].
• Antibody Levels: Some children may have hypogammaglobulinemia, which is a fancy way of saying they have low levels of the antibodies (the body’s “defense soldiers”) needed to fight infection ^[13][14].
• T-Cell Differences: There may also be variations in the types of T-cells (a type of white blood cell) in their blood, which can make it harder for their immune system to “remember” and fight certain viruses ^[1][13].

Monitoring these features through regular check-ups allows you to stay one step ahead, ensuring your child receives support for their bones, eyes, and immune system as they grow.