Every day is a bad hair day

The Case

Diagnosis:Uncombable hair syndrome (pili trianguli et canaliculi)

Uncombable hair syndrome (UHS), or "spun-glass hair," is characterized as frizzy, dry, silvery-blond to straw-colored hair that stands away from the scalp and is unable to be combed flat.^1,2 Only scalp hair is affected, and eyelash, eyebrow, facial, and body hair is normal in appearance.³ The entire scalp typically is involved, but localized forms have occurred in some persons.^1,3 A person's degree of disarray may be related to the number of hairs affected, and approximately 50% of hairs must be affected for clinical changes to become apparent. The quantity, fragility, and rate of hair growth are normal.^3,4 The syndrome is not associated with any physical, mental, or neurologic abnormalities.^1-5 UHS usually becomes evident between 3 months to 3 years of age but can present at any time from infancy to 12 years.¹ It is rare, with fewer than 100 reported cases.

PATHOPHYSIOLOGY

Most cases of UHS are inherited in an autosomal-dominant manner, with either complete or incomplete penetrance, but autosomal recessive and sporadic forms of inheritance have been reported.¹

The pathogenesis of UHS is unclear.² In general, the shape of the inner root sheath establishes the shape and surface of the hair shaft by acting as a rigid structure.¹ It is thought that a misshapen dermal papilla alters the shape of the inner root sheath. Subsequently, the inner root sheath prematurely keratinizes before the central-forming hair, causing focal asymmetry of the hair bulb and lateral loss of hair matrix.^1,3 These abnormalities manifest as a lateral longitudinal groove along the hair shaft. As a result, the hair shaft irregularly twists along its axis at regular intervals, preventing adjacent hair shafts from grouping together in locks, making it extremely difficult to comb.¹

Diagnosis can be confirmed using scanning electron microscopy (SEM) in which the longitudinal grooves along the hair shaft are readily identified.^3,4 Moreover, SEM examination of a cross section of a characteristic hair shaft often reveals that it is triangular, reniform, or heart-shaped in contrast to the normal round to oval outline. To make the diagnosis of uncombable hair syndrome, at least 50% of hairs must be affected, because longitudinal grooves are present in 5% of hairs in the general population.³

TREATMENT

Treatment is limited.² Most persons with UHS note improved manageability by adolescence.^1-5 Some cases even spontaneously regress with time.^2,4 Hair manageability often improves with increased hair length.² Gentle hair care is recommended, although its efficacy is subjective.¹ Patients should use conditioners and soft brushes and avoid harsh hair treatments such as perms, chemical relaxants, or excessive brushing and blow drying. Biotin 0.3 mg 3 times a day for 4 months produced significant improvement in hair combability in 1 patient.