What is the most common site of scabies burrows in adults?

Explanation

## Anatomical Distribution of Scabies Burrows **Key Point:** The interdigital spaces (between fingers) and flexural surfaces of the wrists are the most characteristic and common sites of scabies burrows in adults. These sites are pathognomonic for the disease. ### Classic Distribution Pattern in Adults **High-Yield:** The mnemonic **FWAB** helps recall primary sites: - **F** — Finger webs (interdigital spaces) - **W** — Wrists (flexural surfaces) - **A** — Axillae - **B** — Buttocks and genitalia ### Site-Specific Features | Site | Frequency | Characteristics | |---|---|---| | Interdigital spaces | Most common | Pathognomonic burrows; easily visualized | | Wrist flexures | Most common | Linear or S-shaped burrows | | Axillae | Common | Often with secondary eczematization | | Genitalia/buttocks | Common | Papules and nodules predominate | | Face/neck | Rare in adults | Common only in infants and elderly | | Scalp | Rare | Seen in infants and crusted scabies | **Clinical Pearl:** The absence of burrows on the hands does NOT exclude scabies; however, when burrows ARE present on the hands, scabies is highly likely. Secondary lesions (papules, excoriations, nodules) are more common than primary burrows. ### Why Other Sites Are Less Common - **Face/neck:** Spared in immunocompetent adults due to higher sebaceous gland density and frequent washing; common in infants and immunocompromised patients - **Scalp:** Rarely affected in adults unless crusted scabies or severe infestation - **Palms/soles alone:** Burrows are not limited to these sites; they occur on flexural surfaces and interdigital spaces preferentially [cite:Wolff et al., Fitzpatrick's Dermatology 9e Ch 218]