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Ash leaf spots can be found in tuberous sclerosis, a neurocutaneous syndrome affecting multiple organs. This disorder, affecting about 3 to 10 individuals per 100,000, is autosomal dominant with high penetrance and a high rate of sporadic mutations. The classic triad is seizures, mental retardation, and adenoma sebaceum. Cerebral hamartias (tubers) disrupt the brain structure and may cause seizure activity.
The lance ovate hypopigmented macule (ash leaf macule) is the characteristic lesion of tuberous sclerosis. It was first described by Fitzpatrick et al in 1968, who coined the term lance ovate to describe how one pole of the lesion was rounded and one pole was pointed, which resembled the mountain ash tree leaf. These hypopigmented macules occur in all ages of children. The size and shape of the lesions remain stable with age. They are about 1 to 3 cm in diameter, they can be located anywhere, and perifollicular pigment can appear within the lesion. On the posterior trunk, their long axes are in a transverse direction, whereas on the extremities they are cephalocaudal. The ash leaf macule may be seen in the general population; therefore it is considered only a tertiary criterion for tuberous sclerosis. These macules, however, can be the earliest manifestation of the disease, with more than 32% of patients having white macules and no other cutaneous signs of disease. The ash leaf macule is not the only hypopigmented lesion seen in tuberous sclerosis. In a study of 23 patients, 18 (78%) had hypopigmented lesions, and of these, 10 patients had the lance ovate variety, which made up only about 18% of the total lesions among these 10 patients. The polygonal macule was found to be the most common type of hypopigmented lesion.
The major cutaneous criteria for tuberous sclerosis are angiofibromas (adenoma sebaceum), fibrous plaques, and Koenen tumors. Angiofibromas are often mistaken for acne lesions. These erythematous papules are in a malar distribution, occur after the second year of life, and are found in 80% to 90% of patients. Koenen tumors are periungual and subungual fibromas. Fibrous forehead plaques occur early in life and are believed to be angiofibromas. One child had an elevated, erythematous plaque on his forehead at 4 months of age but did not display the characteristic hypopigmented macules of tuberous sclerosis until 2 years of age. Shagreen's patch is a connective tissue hamartoma.
At times, it may be difficult to distinguish ash leaf macules from macules of vitiligo. Vitiligo lesions, however, tend to be depigmented, symmetric, and progressive. The ash leaf macules are not depigmented but hypopigmented, with functional melanocytes remaining in the affected areas that are normal in number but have smaller melanosomes and melanin content. When examining a child with three or more hypopigmented macules or a lance ovate configuration, a high index of suspicion for tuberous sclerosis is warranted, and examination with a Wood's lamp may reveal occult lesions. There is no treatment for either the hypopigmentation or the underlying disorder.
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