Laboratory Studies
Waardenburg syndrome types 1 and 3 are most commonly associated with point mutations in PAX3, and type 2 is associated with MITF point mutations. Multiplex ligation-dependent probe amplification can be used to detect changes in targeted genes. [24]
Other Tests
Partington used the following three interocular distances for determining the presence of dystopia cantorum (The referent value between distance of the medial canthi of the eyelids and the length between the pupils was 0.6 mm.):
-
Between the inner canthal angles
-
The near papillary distance
-
Between the other canthal angles
Arias and Mota developed the W index, as follows, for the diagnosis of lateral displacement of the inner canthi (A W index of more than 2.07 shows dystopy, while an index of less than 1.87 is normal.):
-
W index = X + Y + alb
-
Where X = [a - {0.21119c + 3.909}]/c and Y = [2a - {0.2497b + 3.909}]/b in mm
-
Distance a is between inner canthi; distance b, between pupils; and distance c, between outer canthi.
Histologic Findings
Histochemical studies in the achromic skin of persons with Waardenburg syndrome show that the melanocytes are absent, or that only a few dihydroxyphenylalanine-positive cells are present.
Ultrastructural observations do not reveal melanocytes, indeterminate dendritic cells, or melanosomes in the keratinocytes of depigmented skin; however, the number of Langerhans cells in the epidermis is normal. The number of melanocytes on the edge of the leukodermas is reduced, and numerous cytoplasmic nuclear abnormalities are noted. Some melanosomes surrounded by a clear halo are found inside of vacuoles. The number of melanocytes in the hypopigmented patches of Waardenburg syndrome is dramatically reduced. These dendritic cells contained poorly melanized melanosomes.
Histopathologic examination of the inner ears of persons with Waardenburg syndrome shows absent organs of Corti, atrophy of the spinal ganglion, and reduced numbers of nerve fibers.
-
Marked facial asymmetry, lagophthalmos, a drooping right corner of the mouth. Image courtesy of Dourmishev LA et al, Cutis 1999; 63:139-40. Copyright 1999, Quadrant Healthcom, Inc.
-
Visage in profile demonstrates absence of nasofrontal angle, eyebrow hypertrichosis, upturned nasal tip, and shortened upper lip with a pronounced cupid's bow. Image courtesy of Dourmishev LA et al, Cutis 1999; 63:139-40. Copyright 1999, Quadrant Healthcom, Inc.
-
Brother and sister with Waardenburg syndrome. Image courtesy of Dourmishev LA et al, Cutis 1999; 63:139-40. Copyright 1999, Quadrant Healthcom, Inc.
