Pallister-Killian Syndrome versus Trisomy 12p-A Clinical Study of 5 New Cases and a Literature Review

Abstract

Pallister-Killian syndrome (PKS) is a rare, sporadic disorder defined by a characteristic dysmorphic face, pigmentary skin anomalies, intellectual disability, hypotonia, and seizures caused by 12p tetrasomy due to an extra isochromosome 12p. We present three cases of PKS and two cases of trisomy 12p to illustrate and discuss features rarely cited in the literature, present certain particularities that not yet been cited, and analyze the differences between entities. Moreover, we present alternative methods of diagnosis that could be easily used in daily practice. Features not yet or rarely reported in PKS literature include marked excess of hair on the forehead and ears in the first months of life, a particular eye disorder (abnormal iris color with pointed pupil), connective tissue defects, repeated episodes of infection and autonomic dysfunction, endocrine malfunction as a possible cause of postnatal growth deficit, more complex sensory impairments, and mild early myoclonic jerks. After performing different combinations of tests, we conclude that MLPA (follow-up kit P230-B1) or array CGH using DNA extracted from a buccal swab is a reliable method of diagnosis in PKS and we recommend either one as a first intention diagnostic test. In cases without major defects associated (suspicion trisomy 12p), subtelomeric MLPA should be performed first.

Keywords: MLPA; Pallister Killian syndrome; array CGH; mosaic; trisomy 12p.

Figure 1

Facial characteristics of patient 1: (a,b) 2 mo of age; (c,d) 3 y and 7 mo of age.

Figure 2

Array CGH result for patient 1—DNA extracted from a buccal swab.

Figure 3

MLPA result for patient 1—DNA extracted from buccal swab. * new version probe P230.

Figure 4

Clinical features of patient 2: (a) 1.5 mo old; (b) 16 y old.

Figure 5

Karyotype for patient 2.

Figure 6

Genetic tests for patient 3: (a) array CGH result—DNA extracted from a peripheral blood; (b) interphase FISH—peripheral blood.

Figure 7

Genetic tests for patient 4. Array CGH result—DNA extracted from a peripheral blood.