Casts and Pseudocasts: Differentiating Hair Shaft Concretions

The document discussed the presence of white/yellow concretions on the hair shaft, which were often mistaken for nits, indicating lice infection. However, these could also be pseudocasts caused by cosmetic hair sprays and dry shampoos. Additionally, inflammatory conditions like psoriasis, seborrheic dermatitis, folliculitis decalvans, and pemphigus vulgaris could lead to hair casts, which are small, movable cylindrical masses formed by hyperkeratotic/parakeratotic cells. Traction alopecia could also result in casts due to the extraction of root sheaths from excessive tension. The document emphasized the importance of distinguishing between casts, pseudocasts, and nits.