A 2-year-old boy with severe generalized erythema and failure to thrive has sparse, brittle scalp hair. Microscopic examination of the hair shaft reveals a ball-and-socket deformity where a proximal cupped end invaginates into a distal bulb. Which condition is associated with this hair shaft abnormality?

• A Menkes disease
• B Netherton syndrome ✓
• C Monilethrix
• D Trichorrhexis nodosa

Explanation

Trichorrhexis invaginata, or bamboo hair, is characterized by a ball-and-socket deformity where the proximal cupped segment invaginates into the distal bulb due to premature keratinization of the cortex. It is pathognomonic for Netherton syndrome, which features erythroderma, bamboo hair, and atopic diathesis. Menkes disease causes pili torti, monilethrix causes beading, and trichorrhexis nodosa causes brush-like breaks.

Reference: Andrews' Diseases of the Skin, 13th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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