Microscopic examination of the hair shaft showed trichorrhexis invaginata (TI). Microscopic examination of the skin revealed a sharply demarcated area of parakeratotic scale adjacent to a normal-appearing epidermis and stratum corneum. The epidermis beneath the parakeratosis was slightly acanthotic in a psoriasiform pattern. A superficial perivascular infiltrate was also present. These findings were consistent with ichthyosis linearis circumflexa.
Netherton syndrome is a rare autosomal disorder of keratinization. Netherton1 first described a case of "bamboo hairs" and ichythosis in 1958. Netherton syndrome is now recognized as a triad of ichthyosis, atopy, and hair shaft abnormalities, which are variably expressed. The pathognomonic feature is TI, an abnormality that is identifiable on light or electron microscopic examination of hair.2 Other observed hair shaft abnormalities include trichorrhexis nodosa and pili torti. The hair appears dull, brittle, and lusterless. The scalp hair, eyelashes, and eyebrows are the most strikingly abnormal, but all the hair is affected. The most common skin manifestation is ichthyosis linearis circumflexa (ILC), which is characterized by migratory, double-edged, scaly plaques. However, other skin manifestations, such as ichthyosiform and pustular erythroderma, may be seen. The clinical picture may be clouded by severe atopic dermatitis. The histopathological features vary with the age of the patient and the lesion but most commonly show a nonspecific dermatitis. More chronic ILC lesions typically show psoriasiform epidermal hyperplasia with a mixed perivascular inflammatory infiltrate.3 Hyperkeratosis, parakeratosis, mononuclear dermal infiltrate, and an absent granular layer have also been reported.4
Abnormal Hair Growth in a Child With Atopy. Arch Dermatol. 2001;137(11):1521-1526. doi: