Table 2 Case reports of spontaneously conceived monochorionic dizygotic twins

Nylander [4]

1970

35

–

–

–

Delivery of heterosexual monochorionic twins: 

Twin A male, weighing 5 lb and 8 oz;

Twin B female: weighing 3 lb and 14 oz

MC placenta

–

First case of MCDZ twins

Quintero [5]

2003

28

MC-DA (I trimester)

18 w: stage I TTTS Laser therapy + reductive amniocentesis

–

miscarriage

MC placenta

Cytogenetic analysis:

-Recipient twin: 46 XX karyotype

-Donor twin: 46 XY karyotype

Molecular analysis using multiple polymorphic microsatellites confirmed dizygosity

First case of MCDZ pregnancy complicated by TTTS

Shalev [6]

2006

39

MC-DA (I and II trimesters)

-

AMNIOCENTESIS for maternal age (-normal male karyotype -47 XY + 21) CORDOCENTESIS

Blood chimerism

Termination of pregnancy:

-normal fetus

-abortus with physical features consistent with Down syndrome

MC placenta

Blood chimerism in MC DZ twins

Lattanzi [7]

2006

33

-

27 w: TRAP s (- inhomogeneus mass without cardiac activity, containing large cystic spaces and no other recognizable visceral structures; -the other fetus: normal)

Not done

SVD at 32 w:

-first baby: male, weighing 1850 gr, non external malformations

-second twin:33 × 40 cm globular mass of tissue, coated by skin and hairs and hair glands, weighing 1070 gr, without upper or lower limbs

MC placenta

-peripheral blood: normal male karyotype in first twin

-skin biopsy and inner mass connective tissue: homogeneous 46 XX karyotype

Sex discordance bw MC twins

Hackmon [8]

2009

33

MC-DA at 12.6 w

–

Not done

SVD at 37 w

MC placenta

-buccal cell DNA: normal 46 XX karyotype in the girl and normal 46 XY in the boy

-lymphocyte DNA: 46 XX [26]/46 XY [24] in the girl and 46 XY [25]/46 XX [25] in the boy

Sex discordance bw MC twins

 Blood chimerism

Umstad [9]

2012

36

MC-DA (12 w)

–

Not done

TTTS stage I Quintero

CD at 36 w after CCS

MC placenta

-Buccal cell DNA: 3 loci shared by the twins

-Leukocyte DNA: 12 of 12 loci shared by the twins

MC Twins DZ in a nonshared tissue, apparently MZ in blood

Kanda [10]

2013

28

MC-DA (I trimester)

Discordant growth pattern

Not done

SVD at 36 w:

-twin 1: phenotypically normal, boy, birthweight 2944 gr

-twin 2: phenotypically normal, boy, birthweight 2502 gr

MC placenta

At 1 month of age:

-blood karyotype (from lymphocytes): 46 XX [5]/ 46 XY [25] in the boy; 46 XY [17]/ 46 XX [13] in the girl

At 6 months of age:

-skin fibroblasts karyotype: normal for both twins

Blood chimerism

Rodriguez –Buritica [11]

2014

21

MC-DA

–

–

CD at 39 w:

-male twin 2300 gr (at 2 months of age: critical aortic stenosis and glanular hypospadias)

-girl 2100 gr

MC placenta

Male twin:

-blood karyotype: 46 XY [14]/ 46 XX [16]

-skin karyotype: 46 XY [18]/ 46 XX [12]

-blood interphase FISH X/Y analysis: 46 XY in 43% 46 XX in 57% Female twin:

-blood karyotype: 46 XX [9]/ 46 XX [21]

-skin karyotype: 46 XX [32]

-blood interphase FISH X/Y analysis: 46 XX in 44.5% 46 XY in 55.5%

Blood and tissue (skin) chimerism

Gabbett [12]

2019

28

MC-DA (I trimester)

Follow up scans: sex discordance bw twins

AMNIOCENTESIS to validate zygosity: 46 XX/ 46 XY chimerism in each twin

CD at 33 w:

Twin1 phenotypically male

Twin 2 phenotypically female

MC placenta

Twin 2:

At 4 w of age a below shoulder amputation due to right brachial artery thromboembolism

At 3 y of age: prophylactic oophorectomy due to gonadal dysgenesis

Sesquizygotic twinning

K. Chen [13]

2020

32

MC-DA at 14 w

Follow up scans: sex discordance bw twins At 28 + 6 TAPS

Not done

Delivery at 31 + 2 w (following CCS and Magnesium sulfate); TAPS confirmed after birth:

-Hb 25.2 g/dL in recipient twin

-Hb 7.5 g/dL in donor twin

Sex discordance confirmed post-natally

MC placenta

Not done

First case of TAPS in MC DZ twins diagnosed prenatally

Armitage [14]

2020

–

MC-DA (I trimester

Follow up scans: TTTS from II trimester

–

CD at 35 w: 2 female twins

MC placenta

Twin A: bilateral retinoblastoma at 7 months of age

Twin B: unaffected

Test on peripheral blood and skin biopsy In both twins:

-Twin A harbored the RBP1 pathogenetic variant in the skin and the blood

-Twin B displayed the RBP1 pathogenetic variant in blood only

Blood confined chimerism

Daum [15]

2020

30

MC-DA

NT: normal Anomaly scan at 17 w: female and male fetuses without malformations

AMNIOCENTESIS to validate zygosity: Dizygotic twins, female and male, with normal karyotypes

CD at 34 w because of TAPS:

-girl, weighing 2150 gr, with Hb 21.8 g/dL

-boy, weighing 2130 gr, with Hb 10.2 g/dL

MC placenta

Cord blood karyotype:

-male: chimerism with 17% 46 XX

-female: chimerism with 27% 46 XY

Buccal smear FISH:

-male: no chimerism

-female: 1% chimerism

2 y follow up buccal smear FISH:

-male: 3% chimerism (46 XX)

-female: 5% chimerism (46 XY)

Non confined blood chimerism

Yoshida [16]

2021

30

MC-DA (I trimester)

Follow up scans: sex discordance bw twins

–

CD at 38 w

Twin A: phenotypically female newborn, weighing 2612 gr;

Twin B: phenotypically male newborn, weighing 2458 gr

MC placenta

Karyotyping on umbilical cord: chimeric karyotypes Twin A 46,XX [15]/46,XY [15] Twin B 46,XY [21]/46,XX [9]

At 7 months of age karyotyping performed from blood samples: chimerich karyotypes: Twin A 46,XY [7]/46,XX [13] Twin B 46,XX [9]/46, XY [11]

At 1 year-old karyotyping from buccal swab cells: normal female and normal male karyotypes: Twin A 46,XX[98]/46,XY [2]

At 3 years of age: blood group: Twins with B/0 chimera

Sex discordant MC DZ twins with chimeric blood group types

J. Chen [17]

2021

–

–

–

–

–

MC placenta

27 years after birth

Peripheral blood

Buccal cells

Twin 1 (male, proband’s brother): has the same

DNA in different tissues

Twin 2 (female, proband): 2 sets of DNA in her blood with 92.84 + 1.80% chimerism; no chimerism in oral mucosa or endometrium

Blood confined chimerism