Symptoms of Sanfilippo Syndrome

Sanfilippo syndrome is a form of childhood dementia. The Cure Sanfilippo Foundation describes the condition as “Alzheimer’s disease in children.” Symptoms usually begin between ages 2 and 6 and become more severe with age.

Behavioral symptoms

Children with Sanfilippo syndrome commonly exhibit behavioral problems, such as hyperactivity, attention difficulties, and severe frustration. Aggression, anxiety, and irritability also are common.

Patients often have characteristics of autism spectrum disorder, such as communication difficulties and self-stimulating behaviors such as flapping hands.

Behavioral problems are frequently reported among the most difficult symptoms to manage, especially early on in the disease. As the disease progresses, they tend to be less burdensome as motor and cognitive problems become more evident.

Developmental delays

Delays in language acquisition in Sanfilippo patients are particularly common, and speech development is usually much more delayed than motor development.

As the children age, they undergo developmental regression (the loss of previously acquired skills), progressively losing motor function and cognitive abilities. This usually starts between ages 4 and 6, though there is substantial variation from person to person and between the different types of Sanfilippo syndrome.

Older children and young adults with the disease usually lose the ability to speak and to walk independently.

Sleep issues

Sleep problems, such as having difficulty falling asleep or frequently waking up at night, are common in children with Sanfilippo. They are typically more evident early on in the disease and become less severe as the patient ages.

Problems related to different body parts

Sanfilippo syndrome is often characterized by a large head size, coarse facial features, excessive growth of coarse or dark hair, and an enlarged liver and/or spleen.

Some patients have mild abnormalities in their skeletal systems, which can result in joint pain or scoliosis (a sideways curvature of the spine).

Enlarged heart and ventriculomegaly (enlargement of fluid-filled chambers in the brain) may also be present.

Infections and digestive problems

Young patients with Sanfillipo syndrome commonly experience infections of the ears, sinuses, and/or throat.

Chronic diarrhea and loose stools are also common, especially among younger patients. Older patients may often experience constipation.

Sensory problems and seizures

Hearing loss and deafness are other common symptoms.

Problems with vision, such as retinopathy (damage to the part of the eye that houses light-sensing nerve cells) are common.

Seizures can occur and tend to become more frequent in the later stages of the disease.


Last updated: March 23, 2021 

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