SNP Shot: Genomic Insights

Snijders Blok-Campeau syndrome is a condition characterized by intellectual disability, speech difficulties, and characteristic facial features.

The degree of intellectual disability in individuals with Snijders Blok-Campeau syndrome varies from mild to severe. Some affected individuals also experience low muscle tone (hypotonia), seizures, or autistic-like behaviors that impact communication and social interactions.

Language development is variable in Snijders Blok-Campeau syndrome. Some individuals develop limited language skills, while others learn only a few words or remain nonverbal. Speech, if it develops, typically begins after the age of two. Affected individuals may exhibit stuttering, problems with mouth and tongue coordination (oromotor dysfunction), or difficulty sequencing sounds and syllables to form words (apraxia). Despite these challenges, individuals with this syndrome are generally very sociable.

Individuals with Snijders Blok-Campeau syndrome often share distinctive facial characteristics. Eye-related features are commonly present, including widely spaced eyes (ocular hypertelorism), deep-set eyes, narrowed eye openings (narrowed palpebral fissures), increased distance between the inner corners of the eyes (telecanthus), and sparse eyebrows. Other possible facial features include full cheeks, a pointed chin, a prominent forehead (frontal bossing), a sunken midface (midface hypoplasia), a broad nasal bridge, low-set and possibly rotated backward ears, and a thin upper lip. Head size may also be affected; most individuals have an unusually large head (macrocephaly), although some have an unusually small head (microcephaly). Premature fusion of certain skull bones (craniosynostosis) can occur in some cases, contributing to an atypical head shape.

Vision problems, such as farsightedness (hyperopia) or misaligned eyes (strabismus), are common in individuals with Snijders Blok-Campeau syndrome.

Approximately half of individuals with Snijders Blok-Campeau syndrome have brain abnormalities, such as enlarged spaces in the brain where cerebrospinal fluid (CSF) accumulates. Less frequently, affected individuals are born with a hole between the heart's upper chambers (atrial septal defect) or another congenital heart defect.

Inheritance:

Snijders Blok-Campeau syndrome is inherited in an autosomal dominant manner. This means that having only one copy of the altered gene in each cell is enough to cause the condition. Most cases arise from new (de novo) gene mutations that occur during the formation of reproductive cells (eggs or sperm) in a parent or during early embryonic development. These new mutations explain why most affected individuals have no family history of the disorder.