Testing the inheritance pattern of palmaris longus muscle absence

Area of Science:

• Human anatomy and genetics
• Anthropology and evolutionary biology

Background:

• The palmaris longus muscle exhibits significant anatomical variability, with absence being a common occurrence.
• While the absence of the palmaris longus muscle is known to be hereditary, its precise genetic transmission pattern remains unclear.

Purpose of the Study:

• To determine the prevalence of palmaris longus muscle absence in a multi-generational family cohort.
• To investigate the inheritance pattern associated with the presence or absence of the palmaris longus muscle.

Main Methods:

• Examined 82 individuals across 20 families, including parents and offspring.
• Assessed palmaris longus muscle presence bilaterally using Schaeffer's test and clinical maneuvers.
• Employed descriptive statistics, including frequency analysis, presented graphically and in tables.

Main Results:

• Palmaris longus muscle absence was observed in 59.75% of individuals, exceeding the presence rate (40.25%).
• Consistent trait transmission from parent to child occurred in 80% of families.
• A generational skip in trait manifestation was noted in 20% of families.

Conclusions:

• The absence of the palmaris longus muscle is a hereditary trait, more frequent than its presence in the studied population.
• Findings support an autosomal dominant inheritance model for palmaris longus muscle absence.
• Incomplete penetrance and variable expressivity of a dominant gene, or potential mutational effects, likely influence this trait.