NeurometPlus

Incidence

Very rare syndrome. Sporadic.

Clinical Characteristics

Chromosome 18, Tetrasomy 18p is a very rare chromosomal disorder in which the short arm of the 18th chromosome (18p) appears four times (tetrasomy) rather than twice in cells of the body. The symptoms of Chromosome 18, Tetrasomy 18p may vary from case to case. Many affected individuals may have abnormalities of the head and facial (craniofacial) area; malformations of the spine, hands, and/or feet; neuromuscular abnormalities, such as increased muscle tone (hypertonia), increased reflex reactions (hyperreflexia), and difficulty coordinating movement; kidney (renal) malformations; and/or additional physical abnormalities. In addition, children and adults with Chromosome 18, Tetrasomy 18p often exhibit moderate to severe mental retardation, limitations in speech, and/or behavioral abnormalities. In most cases, Chromosome 18, Tetrasomy 18p is the result of a spontaneous (de novo) genetic change (mutation) early in embryonic development that occurs for unknown reasons (sporadic). In summary, partial tetrasomy affecting the short arm of chromosome 18 presents with multiple abnormalities which include craniofacial deformities (small head with prominent forehead, facial asymmetry, deformed ears, and pinched nose) and various genital, renal, digital, and other defects.

Precipitants

None

Provocation Tests

None

Diagnostic Procedures

Karyotype. Partial tetrasomy affecting the short arm of chromosome 18