Monodactylous splithand-splitfoot. A malformation occurring in three distinct genetic types

Area of Science:

• Genetics
• Developmental Biology
• Orthopedics

Background:

• Monodactyly is a congenital limb malformation.
• It is associated with several forms of ectrodactyly, a group of genetic disorders.

Purpose of the Study:

• To delineate distinct types of autosomal dominant ectrodactyly associated with monodactyly.
• To describe the clinical and genetic variability within these ectrodactyly types.

Main Methods:

• Clinical observation and family studies of patients with monodactyly.
• Analysis of inheritance patterns, including expressivity and penetrance.
• Genetic analysis to investigate potential mutation types.

Main Results:

• Identified three distinct types of autosomal dominant ectrodactyly presenting with monodactyly.
• Type 1 shows consistent expression and no skipped generations; exceptional cases suggest de novo mutations.
• Type 2 (EEC syndrome) has less frequent monodactyly and more variable limb defects.
• Type 3 exhibits extreme intrafamilial variability, including adactyly and bone defects, with common skipped generations.

Conclusions:

• Autosomal dominant ectrodactyly encompasses diverse phenotypes with monodactyly as a key feature.
• Understanding these subtypes is crucial for genetic counseling and diagnosis.
• Variability in expression and inheritance patterns highlights the complexity of ectrodactyly syndromes.