XK aprosencephaly syndrome

XK aprosencephaly syndrome, also known as XK aprosencephaly-situs abnormality syndrome, is an extremely rare and lethal congenital malformation syndrome characterized by a severe brain defect called aprosencephaly, which represents the most extreme form of prosencephalic developmental failure. In aprosencephaly, the forebrain (prosencephalon) fails to develop, resulting in an absence of cerebral hemispheres and related structures. This condition is even more severe than alobar holoprosencephaly. Affected individuals present with profound craniofacial anomalies including absence of recognizable facial features (aprosopia or severe facial dysmorphism), absence or severe malformation of the eyes, nose, and mouth structures, and microcephaly. Additional features may include situs abnormalities (abnormal positioning of internal organs), limb defects, and other visceral malformations. The condition is incompatible with life, and affected infants are typically stillborn or die shortly after birth. The syndrome was described in siblings, suggesting an autosomal recessive inheritance pattern. The exact genetic cause has not been fully elucidated. Given the lethal nature of this condition, there is no curative treatment. Management, when applicable, is limited to supportive and palliative care. Genetic counseling is recommended for affected families to assess recurrence risk in future pregnancies.

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