Nevoid hypertrichosis and hypomelanosis

ARTICLE

Hypertrichosis may be acquired or congenital, and it may be either localized or generalized [1]. Nevoid hypertrichosis is a type of localized congenital hypertrichosis presenting at birth or soon thereafter in a segmental distribution without abnormal skin pigmentation [2]. In a few cases, multiple lesions of nevoid hypertrichosis have been described, which may be associated with multiple cutaneous or extracutaneous abnormalities [2-9]. Hypertrichosis in these cases may appear as multiple round patches [2, 4-7] or in a checkerboard or linear pattern, reminiscent of Blaschko's lines [3, 5, 7, 9]. We present a case of multiple nevoid hypertrichosis together with a streaky linear hypopigmentation following Blaschko's lines, and suggest the phenomenon of twin-spotting to explain this unusual association.

Case report

A 2-year-old girl was presented for evaluation of congenital skin lesions. She was the first daughter of a non-consanguineous marriage. There were no remarkable personal or familial antecedents. Pregnancy and labor had been uneventful, and the girl was born with a weight of 3.010 kg and a height of 49 cm. At birth several patches of excessive hair growth and four linear hypopigmented lesions were noted. Her postnatal physical and mental development was normal, and her skin lesions remained unchanged.

On examination, we observed a healthy girl showing two types of lesions. On her scapulae, buttocks, arms and legs, symmetrical patches of terminal hair were seen without any pigmentary change of the underlying skin. These patches had a round or oval shape on her trunk (Fig. 1), but lesions on the arms followed a linear pattern. On the left arm, the right side of her trunk and the legs, a streaky linear hypopigmentation was seen (Fig. 2). On her arms and legs, both types of linear lesions ran parallel (Fig. 3). A supernumerary nipple was present on her left side. The rest of physical examination was normal.

Hematologic and biochemical profiles were normal. The karyotype obtained from peripheral blood lymphocytes was normal (46,XY). A skin biopsy from one patch of hypertrichosis showed many terminal hair follicles without smooth muscle hyperplasia and without hyperpigmentation. A skin biopsy from a hypopigmented linear lesion showed a normal appearance in the hematoxylin and eosin staining, but a Masson-Fontana stain revealed an irregular and discontinuous pattern of epidermal pigmentation.

During a follow-up period of 6 years the patient has not experienced any change in the degree of the hypertrichosis or hypopigmentation. Her physical and mental development correspond to her age.

Discussion

The association of nevoid hypertrichosis and hypomelanosis has been only rarely reported, and some of these cases have shown a linear pattern of hypopigmentation. In 1991, Rogers [3] described a girl who had areas of hypertrichosis on the trunk and limbs, partly with a swirled pattern as well as a streaky hypopigmentation reminiscent of hypomelanosis of Ito. In addition, this patient had epidermal nevus-like lesions, nail dystrophy, as well as neurological, gastrointestinal, ocular, pulmonary and skeletal abnormalities. A patient described by Rupert et al. [4] had a patchy congenital nevoid hypertrichosis and hypopigmentation of lesional hair; however, the underlying skin was not depigmented. Chang et al. [5] described a boy with circumscribed areas of hypertrichosis showing a white hair color and slight hypopigmentation of the underlying skin. In some areas, these lesions had a linear arrangement. This patient did not exhibit any other abnormality. A girl described by Ballmer-Weber et al. [6] had hypertrichosis of the genital region and of her shins, in association with hypopigmented lesions following Blaschko's lines on her trunk and limbs. She also had facial dysmorphia, musculoskeletal anomalies, a left groin hernia and mild mental disturbances. Lestringant et al. [7] reported two cases of patchy nevoid hypertrichosis associated with achromic lesions following Blaschko's lines, and mental and skeletal abnormalities. Interestingly, in the second case, hypertrichosis showed a whorled pattern restricted to the normally pigmented skin adjacent to the hypopigmented streaks. A girl reported by Dudding et al. [8] had multiple swirled areas of hypertrichosis without pigmentary changes of the underlying skin and elsewhere two types of lesions, an epidermal nevus on the arm and scalp and hypopigmented lesions following Blaschko's lines on the trunk and limbs. She also had retinal hyperpigmentation. Finally, an unusual case described by Schauder et al. [9] showed linear depigmented hypertrichosis following a broad-band pattern of Blaschko's lines, without pigmentary changes in the underlying skin. This boy had also dysmorphic features as well as severe cerebral and ocular malformations.

The concept of twin spotting involves the presence of two patches of mutant tissue that differ genetically from each other and from the surrounding normal skin [10]. A coexistence of different skin conditions with a genetic origin in the same patient may be explained in that way. In an organism heterozygous for two different mutations located on either of two homologous chromosomes, somatic recombination may result in two different daughter cells homozygous for either mutation, giving rise to two different mutant clones of cells that form paired mutant spots. In our patient, the temporal and spatial proximity of two different skin disorders following Blaschko's lines suggests a phenomenon of non-allelic twin spotting, but this hypothesis awaits testing by molecular analysis.

CONCLUSION

In conclusion nevoid hypertrichosis may occur in a mosaic pattern and may be associated with other cutaneous diseases that show a similar segmental pattern, as a possible twin-spot phenomenon. Moreover, this association may be accompanied, in a number of cases, by severe mental, ocular or musculoskeletal anomalies.

Article accepted on 19/7/02

REFERENCES

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