Postnatal diagnostics of the Pallister-Killian syndrome using interphase nuclei of buccal mucosa by fluorescence in situ hybridization method

Abstract

Aim. Diagnosis of Pallister-Killian syndrome. For the verification of the diagnosis of Pallister-Killian syndrome, children with multiple facial dysmorphia, muscular hypotonia, and retarded growth and development were examined. Material and Methods. The material for conducting cytogenetic examination were lymphocytes of the patients' peripheral blood, analyzed by metaphase plates according to standard methods, not less than 20 cells stained with the G-method. The material for the molecular cytogenetic method on the interphase nuclei (nuc-FISH) was buccal mucosa. The nuc-FISH method was conducted in accordance with the manufacturer's instructions to the probe 12p13/21q22 LSI ETV6 (TEL)/RUNX1 (AML1) ES of Vysis, USA. To confirm the diagnosis, the dual color DNA-label of 12p13/21q22 LSI ETV6 (TEL) / RUNX1 (AML1) ES was used. 100 cells were analyzed, counting the number of signals in each cell. The result was considered positive if three and four green signals of the locus 12p13 shone in each nucleus. Results and Discussion. For three years, in the Specialized Medical Genetic Center, three cases of Pallister-Killian syndrome were observed in children with specific facial dysmorphia, muscular hypotonia, and severe retardation of physical and mental development. All cases were combined with the following phenotype: a flat neck; a prominent forehead; a flat and broad nasal root and a short nose with anteverted nostrils; macroglossia; micrognatia; large ears with thick protruding lobules; sparse anterior scalp hair in infancy; ocular hypertelorism; upslanting palpebral fissures with sparse eyebrows and eyelashes; a long philtrum with thin upper lip and distinct Cupid-bow shape; the fifth finger clinodactyly; the simian crease; a shortened hip bone. No seizures were observed. All children needed an examination of the sound specialist. Occasional abnormalities included the following: in the first case, there was central amaurosis and congenital deafness; the second patient presented with additional breast nipples (six in total); in the third case a congenital heart defect was observed. In all cases, the karyotype of peripheral blood lymphocytes was normal. The result of nuc-FISH of buccal mucosa cells revealed mosaicism signals of 12p13. In medical-genetic counseling of children with symptoms of chromosomal pathology, patients undergo cytogenetic examination according to classical tactics. Obtaining a normal karyotype usually complicates further diagnostics. Taking into account the etiology of Pallister-Killian syndrome, in order to diagnose it, we introduced the nuc-FISH technique on the buccal mucosa cells using a locus-specific probe 12p13. Thus, the diagnosis of Pallister-Killian syndrome in our center has been confirmed in three cases. Conclusions. The clinical presentation of the confirmed cases of Pallister-Killian syndrome corresponds with that described in literary sources. The nuc-FISH method on the buccal mucosa is recommended to be used as a rapid and non-invasive method for diagnosis of Pallister-Killian syndrome.

Keywords

• pallister-killian syndrome, isochromosome 12p, cytogenetic method, nuc-fish method, buccal mucosa