Abstract
J. Elizarrarás-Rivas, R. Fragoso-Herrera, División Genética Humana, Centro de Investigación Biomédica de Occidente CMNO, IMSS. Guadalajara, Jalisco. México (CIBO); L.F. Cerdán-Sánchez, Centro Comunitario de Salud Mental no. 1. IMSS, Zapopan, Jalisco, México; R. Ramos-Zepeda, División de Inmunología, CIBO, México; S.E. Totsuka-Sutto, Departamento de Genética Humana, CUCS. U. de G. Guadalajara, Jalisco. México; P. Gallegos-Arreola, División de Medicina Molecular, CIBO, México; S. Saha, J. McGrath, Queensland Centre for Schizophrenia Research, Wolston Park Hospital, Brisbane, Australia:
Because prenatal brain development is not open to direct scrutiny, researchers interested in neurodevelopmental theories of schizophrenia have studied minor physical anomalies and dermatoglyphic variables [1]. The latter, including epidermal ridges, are formed during the second trimester and remain unchanged thereafter [2]. Therefore, one could hypothesize that factors disrupting prenatal development may also leave a permanent dermatoglyphic record. Indeed, several studies report reduced finger and palm ridge counts in schizophrenia patients compared with controls [3, 4]. We had the opportunity to examine selected dermatoglyphics in a sample from Western Mexico.
The patient group consisted of 20 Mestizos males (an admixture of Spanish, Indian, and Black genetic heritage) with a DSM-IV diagnosis of schizophrenia, based on a structured diagnostic interview. The mean (standard deviation) age of the patients was 35.3 (±8.1). Controls were matched on age (plus or minus one year), sex, ethnicity and place of residence, and screened with a structured interview in order to exclude those with a past history of psychosis, or first or second degree relatives with psychosis. Finger and palm prints of both hands were taken and three dermatoglyphic variables were assessed: (i) total ridge counts (TFRC), (ii) a-b ridge count, and (iii) atd angle. We examined total finger ridge counts when summed for all fingers, and summed for the right and left hands separately. A-B ridge count is the number of ridges intersected by a line drawn between the ‘a’ triradius (at the base of the index finger) and ‘b’ triradius (at the base of the middle finger) of the palm in each hand. The a-b counts for each hand and the sum of both hands were used. The atd angle measures the angle described by lines drawn from the axial triradius ‘t’ at the base of the palm, the ‘a’ triradius and ‘d’ triradius of the palm in each hand. The atd angles for the right and left hands, and the mean of these two values, were used in the analysis. These were scored blind to case-control status, according to standard methods [2]. The study was approved by the Ethics Committee of the Center of Biomedical Investigation and all participants provided written informed consent. Paired t-test was used to compare dermatoglyphic variables between cases and controls.
There were no significant group differences in TFRC (Mean (standard deviation (SD)); Case: 161.10 (±47.39); Controls: 153.20 (±21.12); t 1 = 0.68, p = 0.50), total a-b ridge counts (Case: 89.10 (±13.04); Controls: 83.70 (±6.75); t 1 = 1.39, p = 0.17), nor atd angles (Case: 42.92 (±9.01); Controls: 42.58 (±2.73); t 1 = 0.16, p = 0.88). The result did not change when we examined the right and left hand separately (data not shown).
Mindful of the small sample size, the dermatoglyphic variables did not distinguish people with schizophrenia from well controls. A recent Australian study also found no significant differences in finger ridge counts and a-b ridge counts between cases (n = 240) and controls (n = 228) [5]. The lack of association between dermatoglyphic variables and schizophrenia in our study may reflect ethnic/genetic difference between the Mexican participants and those participants drawn from Ireland and UK where differences have been reported [3, 4]. In addition, perhaps there are regional variations in the prevalence or dose of putative non-genetic factors that may impact on dermatoglyphics and brain development. For example, we have published evidence suggesting that the size of the season of birth effect is positively correlated with latitude in Northern Hemisphere studies (smaller or absent winter/spring excess of schizophrenia births closer to the equator) [6]. Regional variation in the association between dermatoglyphic variables and schizophrenia may be of heuristic value in generating novel candidate exposures.