ARTICLE
Auteur(s) : Antonio TORRELO1, Inmaculada DE
PRADA1, Antonio ZAMBRANO1, Rudolf
HAPPLE2
1 Department of Dermatology and Pathology,
Hospital del Niño Jesús, Menéndez Pelayo 65, 28009-Madrid,
Spain
2 Department of Dermatology, University of
Marburg, Deutschhaustrasse 9, 35033 Marburg, Germany
Article accepted on 12/9/2003
Speckled lentiginous nevus or speckled nevus (SN) is
characterized by numerous small, darkly pigmented speckles on a
background of tannish-brown hyperpigmentation [1]. Sometimes,
however, this tannish background may be very faint or even
invisible [2]. The speckled component may be present at birth or it
appears during childhood. Microscopically, the background
pigmentation corresponds to the features of a lentigo simplex,
whereas the dark speckles usually show a junctional proliferation
of melanocytes [3]. Less frequently, the dark spots may range from
lentigines to compound or intradermal nevi, and cases with a
histopathological appearance of Spitz nevi or blue nevi have
likewise been reported [4].
The typical appearance of SN is that of a round or oval patch of
limited size, but sometimes SN may show an extensive involvement
covering large areas of the skin. Such extensive SN have also been
referred to as “zosteriform” [5], although a careful look at their
distribution reveals a typical checkerboard or flag-like pattern.
This arrangement constitutes one of the well-established patterns
of cutaneous mosaicism [6].
Speckled nevi, particularly those showing an extensive
involvement, may appear in association with various other cutaneous
anomalies. A well-established association of widespread SN and
sebaceous nevus, along with extracutaneous abnormalities, is known
as phacomatosis pigmentokeratotica [7], whereas the coexistence of
large SN and extensive telangiectatic nevus is known as
phacomatosis pigmentovascularis type III [8]. However, a
combination of SN with other types of melanocytic nevi appears to
be exceptional. On the other hand, it is quite common that giant
congenital melanocytic nevi (GCMN) show a somewhat speckled
component, as a result of an uneven melanocyte distribution. In
this way, macular hyperpigmentation with superimposed darker
macules or papules may frequently be seen at the peripheral portion
of a classical GCMN [4]. In such cases, however, the speckled'
component does not exhibit a flag-like pattern. We emphasize that
such speckled' component of GCMN can be distinguished from SN both
clinically and histopathologically.
We describe a boy with classical GCMN who developed during
childhood an extensive, flag-like SN that was partly intermingled
with the GCMN.
Case report
A 2-year-old boy had a large pigmented lesion on his back
present since birth. On examination, this well developed child
showed a giant brown melanocytic nevus covering his lower back.
Some smaller “satellite” lesions were seen on his back, buttocks
and thighs. Their color varied from light-brown to black, and most
of the lesions were covered with dark hair (Fig. 1a). A biopsy was
obtained from a dark lesion, and histopathological examination
showed a typical congenital melanocytic nevus, with nevus cells
penetrating the dermis around hair follicles. A neurological
check-up did not reveal any abnormality. In particular, no
meningeal or medullar melanocytic lesions were noted on a CT scan.
The boy was followed for 3 years and then lost for
follow-up.
The patient returned for evaluation at the age of 15 years.
On examination, we noted some minor changes within the congenital
lesions, consisting of some areas of spontaneous regression and
decreased hair growth. The number of “satellite” lesions on his
buttocks was essentially unchanged. As an additional feature,
however, numerous small, darkly pigmented speckles were noted on
his back (Fig. 1b). These
speckles had appeared around the age of 8. They were arranged in a
segmental pattern on both sides of the body, with a sharp
demarcation at the ventral and dorsal midline (Fig. 2). A
tannish-brown macule was partly underlying the dark speckles on his
right side, whereas otherspeckled areas lacked such background
pigmentation. A biopsy taken from one of these speckles showed a
typical junctional melanocytic nevus (Fig. 3). The patient
was in good health, without any neurological or musculoskeletal
problems.
Discussion
This patient had an unusual association of a GCMN with an
extensive SN that became visible during childhood. For the
following reasons we think that this patient had two different
kinds of melanocytic nevi. Firstly, one of the lesions was present
at birth whereas the other one became visible when the boy was
8 years old. (For obvious reasons this SN was likewise
“congenital” even though it was not visible at birth). The clinical
features of the GCMN and the SN were quite different. The extensive
SN did by no means correspond to a speckled' component of CGMN [4].
The SN extended far beyond the limits of the GCMN, indicating that
the two lesions did not involve the same areas of embryonic
development. Histopathologically, there was likewise a clear-cut
difference between the two lesions. The SN did not show features of
congenital melanocytic nevi but those of a junctional nevus.
Finally, the distribution of the two lesions was different. The SN
was arranged in a checkerboard pattern with a sharp midline
demarcation, whereas the GCMN was located in the middle of the back
without respecting the midline.
This coexistence of two different melanocytic nevi of large
dimensions is highly unusual. We hypothesize that this exceptional
association may represent a further example of twin spotting,
rather than a co-occurrence by chance. Twin spots are patches of
mutant tissue that differ from each other and from the normal
background tissue [9]. In an organism heterozygous for two
different mutations located on either of two homologous
chromosomes, somatic recombination may result in two different
daughter cells that are homozygous for either mutation and give
rise to two different populations of cells forming paired mutant
patches [9]. Perhaps the present case may even be categorized as a
distinct type of phacomatosis for which we propose the term
phacomatosis pigmentosa multiplex, to emphasize the association of
two different hamartomatous pigmentary abnormalities appearing in
the same patient. n
References
1. Stewart DM, Altman J, Mehregan AH. Speckled
lentiginous nevus. Arch Dermatol 1978; 114: 895-6.
2. Maize JC, Ackerman AB. Pigmented lesions of the
skin. Philadelphia, Pa. Lea, Fibiger; 1987: 119.
3. Cohen HJ, Minkin W, Frank SB. Nevus spilus.
Arch Dermatol 1970; 102: 433-7.
4. Schaffer JV, Orlow SJ, Lazova R, Bolognia JL.
Speckled lentiginous nevus. Within the spectrum of congenital
melanocytic nevi. Arch Dermatol 2001; 137: 172-8.
5. Altman DA, Banse L. Zosteriform speckled
lentiginous nevus. J Am Acad Dermatol 1992; 27: 106-8.
6. Happle R. Mosaicism in human skin: understanding
the patterns and mechanisms. Arch Dermatol 1993; 129:
1460-70.
7. Tadini G, Restano L, Gonzales-Perez R, et
al. Phacomatosis pigmentokeratotica: report of new cases and
further delineation of the syndrome. Arch Dermatol 1998;
134: 333-7
8. Ruiz-Maldonado R, Tamayo L, Laterza AM, et
al. Phacomatosis pigmentovascularis: a new syndrome ?
Report of four cases. Pediatr Dermatol 1987; 4: 189-96.
9. Happle R. Loss of heterozygosity in human skin.
J Am Acad Dermatol 1999; 41: 143-64.
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