Netherton's syndrome: increased likelihood of diagnosis by examining eyebrow hairs.

Netherton's syndrome is a rare autosomal recessive condition with variable expression. It comprises an ichthyosiform dermatitis and erythroderma of variable intensity and manifestations, associated with hair abnormalities. The pathognomonic finding (required for diagnosis) is that of trichorrhexis invaginata identified by light and scanning electron microscopic examination of hair shafts. This may be difficult to establish because the hair is sparse and not all hairs exhibit abnormalities. In one patient, cutaneous and hair problems had existed since infancy, and despite repeated examination of scalp hairs, the definitive diagnosis was made only by examining eyebrow hairs at the age of 30 years. We subsequently compared the number of diagnostic lesions found on scalp and eyebrow hairs from two other patients with previously diagnosed Netherton's syndrome. The density of lesions was greater in eyebrow than scalp hair, and furthermore, all eyebrow hairs had at least one lesion. It is proposed that microscopic examination, if possible, of both scalp and eyebrow hair from patients in whom Netherton's syndrome is suspected would increase the chance of a positive diagnosis.