Which syndrome features self-mutilation behavior and is inherited in an X-linked pattern?

• A. Lesch-Nyhan Syndrome
• B. Angelman Syndrome
• C. Fragile X Syndrome
• D. Prader-Willi Syndrome

Answer: (A)

Self-injurious (self-mutilation) behavior is the hallmark feature of Lesch-Nyhan syndrome. This disorder stems from deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT), usually due to mutations in the HPRT1 gene, which leads to excessive uric acid production and a distinctive neurobehavioral profile that includes self-biting and other self-harming acts, along with movement abnormalities. It is inherited in an X-linked recessive pattern, so affected individuals are typically male, with carrier females usually asymptomatic.

The other syndromes do not fit this combination. Angelman syndrome involves a maternal imprinting defect on chromosome 15 and presents with developmental delays, ataxia, and a happy, laughing demeanor. Fragile X syndrome features intellectual disability, distinctive facial characteristics, and often autism, but not the characteristic self-mutilation and X-linked inheritance pattern described. Prader-Willi syndrome is due to a paternal deletion on chromosome 15 and presents with hypotonia, hyperphagia leading to obesity, and hypogonadism, not X-linked inheritance.