Dermatoglyphics and schizophrenia: A comprehensive review of neurodevelopmental biomarkers

Table 1 Summary of twin studies investigating dermatoglyphic abnormalities in psychotic disorders

Study	Location	Twin type	Sample composition	Psychiatric diagnoses	Dermatoglyphic findings
United Kingdom study	Maudsley hospital, United Kingdom	Monozy-gotic	11 normal control pairs; 16 concordant pairs; 9 discordant pairs; 2 triplets (1 concordant, 1 partially affected)	Psychosis	RD and APFC abnormalities mirrored psychosis discordance in discordant twins
United States study	NIMH twin registry, United States	Monozy-gotic	31 discordant pairs; 20 SZ/schizoaffective; 8 bipolar; 3 other psychosis; 19 concordant pairs; 11 SZ/schizoaffective; 3 SZ + schizotypal; 5 mixed psychosis/affective/schizotypal	Schizophrenia, bipolar, schizoaffective, other psychosis	Investigated RD and APFC to test whether dermatoglyphic discordance parallels clinical discordance

APFC: Abnormal palmar flexion creases; RD: Ridge density.

Table 2 Prevalence of dermatoglyphic abnormalities among monozygotic twin pairs discordant and concordant for psychotic disorders

Twin pair type	Psychosis status	APFC (%)	RCD (%)	Any abnormality (APFC or RCD, %)
Discordant twins (n = 31)	Affected twin	36.0	9.7	Significantly higher than non-affected
	Non-affected twin	16.0	6.5	Lower than affected co-twin
Concordant twins (n = 19)	Affected twins (both)	32.4	10.5	Moderate

APFC: Abnormal palmar flexion creases; RCD: Ridge count dissociation.