## Most Common Sites of Scabies Infestation **Key Point:** The interdigital spaces (web spaces between fingers) are the most common and characteristic site of scabies infestation in adults, followed by flexural surfaces of wrists, elbows, axillae, and genitalia. ### Anatomical Distribution by Site Frequency | Site | Frequency in Adults | Clinical Significance | |------|---------------------|----------------------| | Interdigital spaces | Most common | Diagnostic hallmark; mites burrow here first | | Flexural wrists | Very common | Often bilateral; easily visible | | Axillae | Common | Warm, moist environment favors mites | | Genitalia | Common | Especially in males; pruritus may be severe | | Inframammary fold | Common | Warm, occluded area | | Scalp/hair | Rare in adults | More common in infants and immunocompromised | | Face/neck | Rare in adults | Atypical presentation; suggests immunosuppression | **High-Yield:** The **interdigital spaces** are pathognomonic for scabies and should always be examined first. Finding a burrow here confirms the diagnosis. **Clinical Pearl:** In infants and young children, the scalp, face, palms, and soles are more commonly affected than in adults. In elderly and immunocompromised patients, atypical distribution (including face and scalp) is seen. **Mnemonic:** **FANG** — Flexural surfaces, Axillae, Nipples (inframammary), Genitalia — common sites in adults after interdigital spaces. ### Why Interdigital Spaces? 1. **Warm, moist, occluded microenvironment** — ideal for mite survival and reproduction 2. **Thin stratum corneum** — easier for mites to burrow 3. **Frequent hand contact and friction** — mites prefer areas of friction and moisture 4. **Initial site of infestation** — mites typically enter via hands during close contact [cite:Irvine 5e Ch 14]
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