Hair shaft abnormalities

Large, unevenly spaced ‘bubbles’ that enlarge and thin the hair cortex on microscopy; fractures occur at sites of large ‘bubbles’; due to trauma

Beaded appearance of hair due to periodic thinning of hair shaft (like necklace or string of beads) → normal at birth, few months later with short, fragile brittle hair

‘Bamboo hair’; microscopic appearance showing ball and socket or collapsible telescope

{Seen in Netherton’s syndrome}

Incomplete fracture with frayed ends resembling two paint brushes against eachother

{Seen in Menkes disease, trichothiodystrophy, arginosuccinic aciduria, Netherton’s syndrome}

Sulfur-deficient hair with alternating light and dark bands under polarizing light

Twisting and flattening of hair fiber

{Seen in Björnstad syndrome, Crandall syndrome, Menkes diseases, Netherton’s syndrome}s

Clean transverse fracture of hair shaft; mechanical or acquired

{Seen in trichothiodystrophy}

Alternating bright and dark bands seen in hair shaft with reflected light; light bands due to abnormal air-filled cavities with ↑ light reflex (but on microscopy appear paradoxically dark); may be sporadic or familial, may have normal hair length

{Unlike trichothiodystrophy where banding only seen with polarizing light}

‘Split ends’; longitudinal splits in hair shaft originating at free end, due to trauma

Knots develop within curly hair due to excessive combing or rustling of hair

‘Ingrown hairs’ or pseudofolliculitis barbae; hair exits skin surface and then re-enters causing foreign body response

Hair trapped in stratum corneum and subsequently appearing as dark coiled ring; may be due to friction or associated with keratosis pilaris

Two hairs, which occupy same follicle, bifurcate and then rejoin; each branch has its own cuticle

Multiple hair shafts from one papilla; each fiber has its own inner root sheat but fibers share common outer root sheath

Small vellus hairs embedded within hair follicle and confused with open comedones; typically seen on nose, forehead, cheeks and neck

Multiple abnormalities causing woolly hair; may see elliptical cross-section, axial twisting, breaks and splitting; isolated or familial

{Seen in Carvajal and Naxos syndrome}

‘Spun glass hair’; premature keratinization of the inner root sheath; triangular cross-section with central linear groove along one side

{Seen in uncombable hair syndrome}

Acquired curling of the scalp hair; isolated or due to trauma, medications or trichotillomania

Ruffled proximal cuticle, absence of root sheath

{Seen in loose anagen hair syndrome}

Cylindrical rings of keratin that move freely along hair shaft (likely represent shed inner root sheath); differentiate from nits (which do not freely slide off)