Pseudohyperphalangism in fetal Dilantin syndrome

Area of Science:

• Medical Genetics
• Developmental Biology
• Teratology

Background:

• Fetal Dilantin Syndrome (FDS) is a spectrum of birth defects associated with prenatal exposure to phenytoin (Dilantin).
• Digital anomalies, including brachydactyly and clinodactyly, are recognized features of FDS.
• Hyperphalangism, characterized by an extra phalanx in a digit, is less commonly described in FDS.

Purpose of the Study:

• To describe a unique digital anomaly observed in siblings diagnosed with Fetal Dilantin Syndrome.
• To differentiate this observed anomaly from true hyperphalangism.
• To contribute to the understanding of skeletal manifestations in Fetal Dilantin Syndrome.

Main Methods:

• Clinical observation and examination of three siblings presenting with Fetal Dilantin Syndrome.
• Radiographic analysis to assess bone structure and identify digital anomalies.
• Comparison of the observed anomaly with the characteristics of true hyperphalangism.

Main Results:

• Apparent distal hyperphalangism was identified in all three affected siblings.
• Radiographic findings indicated that the anomaly was due to the division of a normal phalanx, not the presence of an extra one.
• Other characteristic stigmata of Fetal Dilantin Syndrome were present in the affected individuals.

Conclusions:

• The observed digital anomaly in these FDS siblings represents a phalanx division, mimicking hyperphalangism.
• This finding expands the spectrum of digital malformations associated with Fetal Dilantin Syndrome.
• Distinguishing between phalanx division and true hyperphalangism is crucial for accurate diagnosis and understanding of FDS pathogenesis.