During a well-child examination, the mother of a two-month-old adopted infant expressed concern about a patch that she had recently noticed on the baby's skin. The infant had normal health, growth, and development up to this point. On examination, a solitary, ovoid, hypopigmented lesion was noted on the upper chest (see accompanying figure). The lesion was devoid of any scale or signs of inflammation. When pressure was applied to the lesion with a glass slide, it did not change color. A Wood's lamp examination of the skin made the macule prominent. A potassium hydroxide preparation of the skin was unremarkable.
The answer is E: tuberous sclerosis. Tuberous sclerosis is a multisystem autosomal dominant disorder classically defined by the triad of congenital hypopigmented macules, seizures, and mental retardation. However, because of variable penetrance, the prominence of these findings varies in severity.1 Abnormalities primarily involve the skin and nervous system with the development of various visceral tumors. Genetic counseling is recommended in persons with a family history of tuberous sclerosis. However, most cases are not familial.2
Hypopigmented macules, also known as “ash-leaf spots,” can be present at birth and are most common on the trunk and lower extremities. They appear in 80 percent of persons with tuberous sclerosis by one year of age. Thus, they are the earliest indicator of this disorder.3,4 Affected patients also may have had a white tuft of scalp hair since birth. A Wood's lamp examination helps identify hypopigmented lesions because areas with reduced or absent melanin do not absorb the light and appear lighter than normal skin.
Other skin lesions include papules or nodules (usually on the center of the face), plaques, and periungual papules or nodules. Facial angiofibromas (i.e., adenoma sebaceum) are pathognomonic but do not appear until the third or fourth year of life. The shagreen patch, a fleshy, irregular plaque often found on the lower back, is another characteristic finding in patients with tuberous sclerosis.
Hypopigmented macules are more common in the general population than previously believed. Most persons with one to three hypopigmented macules will not be at risk to have or transmit tuberous sclerosis.4 The presence of a few hypopigmented macules on the skin of an otherwise healthy person without a family history of tuberous sclerosis need not prompt a work-up for this disorder. However, children with such macules should be closely monitored for development of new macules or other disease manifestations, especially if they have a family history of tuberous sclerosis.
Café au lait spots are hyperpigmented lesions that occur in up to 2.5 percent of newborn infants and in 10 to 15 percent of adults. The presence of these spots in infants often prompts concern about neurofibromatosis. Well-defined consensus criteria exist for the diagnosis of neurofibromatosis. A diagnosis of neurofibromatosis type 1 in infants requires the presence of one other feature and six or more café au lait spots greater than 0.5 cm in diameter (or greater than 1.5 cm in diameter in adults).5
Hansen's disease, caused by Mycobacterium leprae, should be suspected in a person from an endemic area who has a hypopigmented macule with diminished or absent sensation. Biopsy shows granulomatous disease.
Nevus anemicus is a “pharmacologic nevus” caused by a hypersensitivity of the blood vessels within the nevus to circulating catecholamines, causing vasoconstriction and pallor.2 This asymptomatic lesion lacks scales and has normal histology. When pressure is applied to the lesion with a glass slide, the lesion becomes difficult to differentiate from the surrounding normal skin. A Wood's lamp examination does not accentuate this lesion. No treatment is needed.
Tinea versicolor, a fungal skin infection caused by Malassezia species, is unusual during infancy but is common in adolescents and young adults. Lesions typically are multiple, asymptomatic macules with fine scales and are more common on the face in children; upper trunk involvement is more common in adults. In most cases, an orange fluorescence is visible during a Wood's lamp examination. A potassium hydroxide preparation shows spores with fungal hyphae (“spaghetti and meatballs”) under the microscope.
|Hansen's disease (leprosy)||Mycobacterial disease; macule with diminished sensation|
|Nevus anemicus||Solitary asymptomatic macule; pressure causes macule to transiently blend in with surrounding normal skin|
|Tinea versicolor||Fungal etiology; multiple asymptomatic macules with fine scales; more common in adolescents|
|Tuberous sclerosis||Solitary or multiple, asymptomatic, “ash-leaf spots” without scaling; Wood's lamp makes lesions prominent|