Chromosomal Disorders

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29. The correct answer is E. This patient has thymic aplasia (DiGeorge syndrome), in which the third and fourth pharyngeal pouches, and thus the thymus and parathyroid glands, fail to develop. This disease often presents with congenital defects such as cardiac abnomalities, cleft palate, and abnomal facies. Patients suffer frequent viral and fungal infections because of T-cell deficiency. Answer A is incorrect. High IgM levels and nomal T cell number are suggestive of hyper IgM syndrome, in which B cells are unable to class switeh because of a defect in helper T cells. Patients have normal numbers of T cells and high IgM level; levels of IgA, IgE, and IgG are low. Answer B is incorrect. Hypogammaglobu-linemia with normal T cell number is characteristic of Bruton agammaglobulinemia, an X-linked defect in a tyrosine kinase that is necessary for B cell maturation. After six months of age, when the levels of matemal antibodies have declined, patients with the disease tend to present with recurrent bacterial infections. Answer C is incorrect. Hypogammaglobu- linemia with reduced T cell mumbers is sug- gestive of severe combined immunodeficiency (SCID). SCID presents with recurrent viral, bacterial, fungal, and protozoal infections due to a total lack of cellular immunity second- ary to a stem cell deficit in the bone marrow. SČID does not present with the congenital defects described in the vignette. Answer D is incorrect. Low IgM levels and nomal T cell numbers are typical of Wiskott- Aldrich syndrome, an X-linked defect associated with elevated IgA levels, elevated IgE levels, normal IgG levels, and low IgM levels. It involves a defect in the body's ability to mount an IgM response to bacteria. Patients have a nomal number of T cells, but their T cells re- spond ineffectively to antigens. Recurrent pyogenic infections, eczema, and thrombocytope- nia are the typical symptoms Wiscott-Aldrich syndrome does not present with any specific enzyme abnommality.

29. A neonate who is born with a cleft palate and abnormal facies becomes cyanotic and hypoxic soon after birth. On physical examination, the neonatologist hears a crescendo-decrescendo murmur with a harsh systolic ejection. Further investigation shows tetralogy of Fallot. Exami- nation of this patient's serum is likely to reveal which of the following? A) High IgM and normal T cell number B) Hypogamı maglobulinemia and normal T cell number C) Hypogammaglobulinemia and reduced T cell number D) Low IgM and normal T cell number E) Reduced T cell number alone

Edwards syndrome (trisomy 18)

2nd most common autosomal trisomy resulting in live births?

46 XX or XY denovo(non inherited) microdeletion of the short arm of chromosome 5 also called 5p syndrome

4 year old baby comes with a cat like cry on karyotype analysis what is shown?

FISH analysis of chromosome 5 only 1 ch. 5 p will light up and be shown because fluroscent probe base pairs to one part of ch. 5 not both because other chromosme has a microdeletion of 5 p . Without microdeletion both chromosome 5p short arm will light up because the flurescent probe base pairs to both 5p

4 year old came with cat like cry but normal karyotype whats the next step?

46. The correct answer is E. The child is present- ing with DiGeonge wyndrome, which is due to abnomal development of the third and fourth branchial (pharyngeal) pouches. This leads to hypoplasia of the thymus and parathyroid glands. Without a properly functioning thyms, Tlymphocyte maturation fails, resulkting in impaired cell-mediated immunity. Thus, pa- tients with DiGeorge syndrome often present with recurrent viral and fungal infections, as in this patient Without adequate poduc tion of parathyroid hormone, these patients are often hypocalcemic, leading to tetany and seizures. DIGeorge syndrome can be summarized by the mnemonic CATCH-22: Cardiac defects, Abnormal facies, Thymic hypoplasia, Cleft palate, and Hypocalcemia due to a microdele- tion on chromosome 22 Anwer A is incomect. The fint and second branchial arches play no role in DiGeorge syndrome. For first-arch derivatives, think "M: Mandible, Malles, spheno Marndibular ligament, musdes of Mashication (teMporalis, Masseter, Modial and lateral pterygids). The first arch is associated with cranial nerve V. For second-arch derivatives, think "S": Stapes, Sty- loid process, Stylolynid ligament, muscles of facial expression, Stapedius, Sty lohyoid, Cra- nal nerve VII is associated with the second arch. Answer B is incomect. The first branchial pouch arises in the pharynx and estends later- ally and cephalad to contact the finst branchial deft, forming the eustachian tube. The second branchial pouch originates in the oropharynx and contributes to the middle ear and tonsils They are not involved in DiGeorge wndrome. Answer C is incorrect. The fourth and sith pharyngeal arches do not play a role in Di George syndrome. The fouth arch is respon- sible for museles of the soft palate (but not the tensor veli palatini, a first arch derivative), the muscles of the pharynx (except the shlopharynges), the ericothyroid, and the aortic arch. Founth-arch muscles are innervated by the su- perior laryngeal branch of cranial nerve X. The sixth arch produces the muscles of the laryns (except for the cricothyroid) as well as the pul- monary arteries. These museles are innervated by the recunent laryngeal branch of cranial nerve X Answer D is incorrect. The second through fonurth branchial defts form temporary sinuses but are obliterated before maturation. Thus, they have no derivatives in the adult

46. A 4-month-old girl who was born full-term presents to her pediatrician with an upper res- piratory infection. Her mother notes that this is the fifth time her daughter has had an upper respiratory infection since birth. Her past med- ical history is significant for seizures shortly after birth. In addition to pulmonary findings, the physical examination is notable for oropha- ryngeal candidiasis that the patient's mother has been occurring regularly. This child is says presenting with a syndrome that is due to ab- errant development of which of the following embryonic structures? A) First and second branchial arches B) First and second branchial pouches C) Fourth and sixth branchial arches D) Second and third branchial clefts E) Third and fourth branchial pouches

9. The correct answer is B. This patient's recur- rent viral and fungal infections and hypocalce- mia are consistent with DiGeorge syndrome. This condition is caused by the failure of de- velopment of the third and fourth pharyngeal pouches, and thus the thymus and parathyroid glands. The recurrent viral and fungal infec- tions are caused by a T-lymphocyte deficiency. In lymph nodes, T lymphocytes are found in the paracortical region, thus this region is often underdeveloped in patients with DiGeorge syndrome. Answer A is incorrect. Follicles are areas of mostly B-lymphocyte aggregation, and are not usually affected in DiGeorge syndrome. Answer C is incorrect. The medullary sinuses contain macrophages and communicate with lymphaties. Answer D is incorrect. This pattern is characteristi of follicular lymphoma, not DiGeorge syndrome. Answer E is incorrect. The medullary cords contain lymphocytes and plasma cells, and are not usually affected in DiGeorge syndrome.

A 3-year-old boy is admitted to the hospital with aspergillosis. He has had multiple admis- sions for viral and fungal infections previously. His serum calcium level is 7.8 mg/dL. Biopsy of one of this patient's lymph nodes would most likely reveal which of the following abnormalities? A) Decreased number of follicles B) Hypocellular paracortex C) Hypocellular medullary sinuses D) Enlarged follicles throughout the entire lymph node E) Increased number of the medullary cords

C- digeorge syndrome Deletions involving the long arm of chromosome 22 can result in facial, cardiac and immunological abnormalities. DiGeorge syndrome is one such manifestation. DiGeorge syndrome is defined by thymic aplasia and failure of parathyroid formation, due to defective embryonic development of the third and fourth pharyngeal pouches. Patients typically present with hypocalcemic tetany and recurrent viral and fungal infections due to T-cell deficiency. Cardiac defects associated with this syndrome are Tetralogy of Fallot and interrupted aortic arch. Chromosome 22q11.2 deletion is found in 90% of cases of DiGeorge syndrome. ( Choice A) Kartagener syndrome produces immotile cilia due to an autosomal recessive microtubular defect. Male infertility, recurrent sinusitis, and bronchiectasis result. There is an association with situs inversus. ( Choice B) Tuberous sclerosis is an autosomal dominant syndrome characterized by cutaneous angiofibromas (adenoma sebaceum), seizures, and mental retardation. Pathological lesions include CNS hamartomas and benign neoplasms, renal and other visceral cysts, a variety of other hamartomas, and cardiac rhabdomyomas. ( Choice D) Friedreich's ataxia is an autosomal recessive spinocerebellar degeneration with predominantly spinal ataxia. It is not usually associated with facial or palatal malformations, but can be associated with hypertrophic cardiomyopathy. ( Choice E) Marfan syndrome is an autosomal dominant defect in a connective tissue glycoprotein that can cause cystic medial necrosis of the aorta. It is not often associated with a cleft palate, but rather a high arched palate, crowded teeth, and a narrow face. (Choice F) Down syndrome results from trisomy 21. Patients have flat facies, prominent epicanthal folds, and occasionally a cleft palate. ( Choice G) Turner's syndrome is an XO sex chromosome disorder resulting in short stature, webbed neck, ovarian failure, and possible coarctation of the aorta. Educational Objective: A variety of genetic disorders can result in facial and/or palatal malformations, including deletions of the long arm of chromosome 22. However, deletions involving the long arm of chromosome 22 are also associated with DiGeorge syndrome (congenital thymic and parathyroid aplasia, congenital cardiovascular anomalies).

A Caucasian newborn with facial dysmorphia and cleft palate is found to have a deletion involving the long arm of chromosome 22. These findings are most consistent with: A. Kartagener's syndrome B. Tuberous sclerosis C. DiGeorge syndrome D. Friedreich's ataxia E. Marfan syndrome F. Down syndrome G. Turner's syndrome

Prenatal diagnosis before birth 1-Serum markers 1st trimester** Bhcg and PAPP-A decreased 2nd trimester **** All markers normal BHCG PAPP-A (pregnancy associated plasma protein A)estriol(UE3 unconjugated estriol) and AFP so these tests are misleading *****! for patau 2- Prenatal ultrasound Nuchal translucency 3- karyotype analysis- before birth amniocentesis confirms it ==================================== After birth blood test karyotype

A mother with a child with small eyes small extra fingers scalp lesions and is pregnant currently and is afraid of having another baby with that Same condition. What are some screening tests that can be done

E-t cells

An 8-year-old male patient is brought to a rural hospital with a history of recurrent infection. The patient has a characteristic facies with a high, broad nasal bridge, long face, narrow palpebral fissures, and an abnormally small mandible. The patient also has a cleft palate. The patient is diagnosed with DiGeorge syndrome, an inherited immunodeficiency disease due to a chromosome 22q11.2 deletion. In this syndrome, the production of which of the following cells is affected in the thymus? A) B cells B) endothelial cells C) macrophages D) neutrophils E) T cells

C inc FSH Diagnosis Blood test estrogen dec FSH and LH inc Karyotype analysis before birth by chorionic villus sampling, amniocentesis or after birth by blood test Imaging- US cystic hygroma, horse shoe kidney MRI/echo can show CVS anomaly

Choose answer and other diagnostic tests

Down Syndrome (Trisomy 21) Most common viable chromosomal disorder and most common cause of genetic intellectual disability Mental retardation 3 hallmarks (flat face;epicanthal fold; simian crease) Flat face**** Epicanthic fold *** Brushfield spots (on iris) Simian crease single paplmar crease Incurved 5th finger Gap between first and second toes Complications the 5 As of Downsyndrome Associated with 1-ADVANCED MATERNAL AGE CNS 2-Alzheimer's disease early onset Cvs 3-AV septal defect (endocardial cushion defects septum separating chambers not formed properly) Git- Atresia duodenal " double bubble sign" no food pass through duodenum because complete closure of duodenum 2 gas bubbles in stomach and duodenum and Hirschsprung disease? Hematology AML/ALL

Clinical features of this patient

Mental retardation Microcephaly Hallmark/pathognomonic features 2 prominent occiput and micrognathia**** Low set ears ; cleft lip nd palate Clenched hands (hypertonic) & overlapping fingers(4th and 5th digits) Rockers bottom feet Limited hip abduction bc hypertonic Cvs congenital heart disease (septal defects) Git omphalocele, esophageal atresia Renal horseshoe kidney

Clinical features of this patient

Ovarian dysgenesis(streak ovaries)- dec estrogen leads to inc FSH and LH, menopause before menarche , most common cause of primary ammenorrhea Lymphatic defects- low posterior hairline(not lymphatic defect) and webbed neck because child had cystic hygroma(lymphatic defect) that dec with age and left extra skin Lymphedema of hands and feet by lymphatic not developed Skeletal abnormalities -shot stature(by of one SHOX gene is absent( short stature homeobox, embryonic regulation of skeletal system especially arms and legs) high arched palate, broad chest with widely spaced nipples; cubit is valgus(arms turned outward); shortened 4th metatarsal CVS- bicuspid aorta, preductal coarcation of aorta( hypertension of upper extremities femoral pulse less and weak than brachial pulse Renal-horse shoe kidney

Clinical features of this patient

Patau is a defect of the mid face ; eye; forebrain development CNS/head Mentally retarded Holoprosencephaly(forebrain of embryo fail to divid into hemisphere 2 hallmarks*** Microcephaly and Micropthalmia (small eyes or single eye cyclopia by 2 orbits that can't divide into 2 cavities Cleft lip and palate Cutis aplasia(scalp lesions without skin) Cvs Septal defects( Congenital heart disease) Git-omphalocele(bowel herniate into umbilical cord umbiblical hernia) Polydactyl (many fingers or toes) and clenched fist Rockers bottom feet Renal Polycystic kidney disease

Clinical features of this patient

testicular atrophy, sterile/infertility issues (dec sperm) one of the most common cause of hypogonadism seen in infertility work up tall, long extremities, Female body= Eunochoid body shape gynecomastia, (increased risk of breast cancer) Female hair distribution Weaker bones(increased risk of osteoporosis) inactivated X chromosome, -dysgenesis of seminiferous tubules, decreases inhibin leads to inc FSH) -abnormal leydig cell function Dec testosterone inc LH and this inc estrogen The extra x increases estrogen to testosterone ratio Al so due to dec testosterone and inc estrogen Dec testosterone dec testes maturation, dec sperm production and no development of secondary male sexual characteristics

Clinical features of this patient

Gonadoblastoma Mosaic turner

Her karyotype is 45XO/46XX she has an increased chance of

Turner's Syndrome (XO) important feature menopause before menarche

Most common cause of primary ammenorrhea

Head-microcephaly, mental retardation Eyes-Hypertelorism(widely spaced eyes), epicanthal fold Nose-Wide Broad nose High arched palate Other features Cat like cry hall mark for cri du chat( genes for larynx development deleted so larynx do not develop) also have swallowing difficulties leads to failure to thrive and developmental delay also speech issues. Hypotonia Congenital heart defect vsd

Name labeled areas

Flat facial features and excessive skin at the nape of the neck are two of numerous phenotypic features associated with Down syndrome (trisomy 21). Other classic phenotypic findings include slanted palpebral fissures and a single transverse palmar crease. Visceral anomalies are common. Cardiac defects are found in approximately half of all infants with Down syndrome, with the endocardial cushion defect (atrioventricular septal defect) and ventricular septal defect most often seen. Gastrointestinal tract abnormalities are also identified in 10-15% of this patient population, and can include duodenal atresia, Hirschsprung's disease, and tracheoesophageal fistula. Down syndrome incidence increases with maternal age. The vast majority of cases arise due to chromosomal nondisjunction during maternal meiosis I, which results in a full trisomy 21 present at conception. ( (Choice B) Trisomy 18 (Edwards syndrome) often results in fetal death. Clinical manifestations in liveborn infants include prominent occiput, micrognathia, small mouth, low-set and malformed ears, and rocker-bottom feet. Clenched hands with the index finger overriding the middle finger and the fifth finger overriding the fourth finger are characteristic for this condition . (Choice C) Trisomy 13 (Patau syndrome) often results in fetal death. Clinical manifestations in liveborn infants include cleft lip and palate, polydactyly, microcephaly, rocker-bottom feet and umbilical hernia. Cardiac and renal defects are usually present. ( (Choices D, E, and F) Karyotypes 47,XXX, 47,XXY (Klinefelter syndrome), and 47,XYY do not cause death in utero. Newborns with these karyotypes are phenotypically normal with no obvious dysmorphism. ( (Choice G) Stillborn fetuses with Turner syndrome (45,XO) are likely to have edematous hands and feet, cystic hygroma of the neck, and coarctation of the aorta. Turner syndrome is not associated with flat facial features, ventricular septal defects, or duodenal atresia Educational Objective: Down syndrome (trisomy 21) occurs in approximately 1 in 730 live births. The majority of fetuses with this chromosomal defect die in utero. The triple marker test, quadruple marker test, and integrated test allow for Down syndrome screening. Amniocentesis and chromosomal analysis of fetal cells can be used to verify the diagnosis.

T

Numerical cause -most commonly prezygotic non disjunction in meiosis 1 or 2(usually from sperm paternal gamete) -next post zygotic nondisjunction in Mitosis Structural cause -Isochromosome - deletion of part of X chromosome

The Pathophysiology of this is

No just supportive

The mother is 38 years old she Delivered a new born that appears to have a small head with small eyes karyotype analysis shows 47XY +13 is there treatment

Trisomy 13: Patau Syndrome (47,+13)

The mother is 38 years old she Delivered a new born that appears to have a small head with small eyes with extra fingers and scalp lesions the baby has ?

Advancing maternal age Family history( another baby with patau)

The mother is 38 years old she Delivered a new born that appears to have a small head with small eyes with extra fingers and scalp lesions. also mentions her other baby has a similar condition what are the the risk factors in this patient ?

Death before age 1

The mother is 38 years old she Delivered a new born that appears to have a small head with small eyes with extra fingers cleft lip and palate what's the survival rate for this baby?

Down syndrome is the most common chromosomal abnormality, and the second most common cause of mental retardation tis associated with advanced maternal age and can be dagnosed prenatally Triple test performed at wecks 16-18 of gestation, detects low alpha fetoprotein (AFP) levels. A finding of low AFP on triple test is of an indication for amniocentesis Karyotyping of associated fetal cells with a contained diagnosis in amniotic Down flud can syndrome, diagnose and is Down therefore syndrome About 90% of patents with Down syndrome have trisomy 21. The parents of these patients are normal, and with the abnormality arising as a consequence of meiotic non-dysjunction (tailure of chromosome 21 to divide during meiosis) This abnormality occurs in the ovum, thus explaning the association of Down syndrome with increased maternal age ( (Choice B) Omphalocele causes increased AFP levels in maternal serum and amniotic fluid. High AFP is also associated with gastroschisis, multiple gestation and neural tube defects ( (Choice E) Neural tube defects are associated with increased AFP levels and increased acetylcholinesterase levels in amniotic fluid (Choices A and D) Turner's syndrome and fetal alcahal syndrome do not cause abrormal AFP levels. Educational Objective: 1 Elevated alpha fetoproten levels are seen in mutiple gestation, neural tube defects (ncluding spina bifida, anencephaly), and abdominal wall defects. 2 in contrast, Down syndrome is associated with low alpha-fetoprotein levels in maternal senam and amniotic fud The defintive prenatal diagnosis is made by karyotyping of tetal cels

What are other tests that can be a prenatal diagnosis for Down syndrome

Karyotype confirms klinefelter Other tests for diagnosis -Karyotype before birth by amniocentesis Or after birth with blood test(karyotype) -blood test- testosterone dec leads to inc FSH and LH Estrogen/testosterone ration increased -semen analysis low sperm count

What are some other tests that can also be done

Patau syndrome 47 xx/xy +13 Edward syndrome 47 xx/xy + 18 Down Syndrome 47 xx/xy +21

What are the only 3 autosomal trisomies that can be compatible with life

Prenatal diagnosis First trimester Prenatal diagnosis before birth 1-Serum markers 1st trimester** Bhcg and PAPP-A decreased 2nd trimester **** BHCG, AFP , estriol all decreased inhibin normal or dec. 2- Prenatal ultrasound Nuchal translucency polyhydramnios (esophageal atresia wont allow AF to be swallowed) 3- karyotype analysis- before birth amniocentesis confirms it ================================= After birth blood test karyotype

What would have been some tests to diagnose this condition before delivery

Klinefelter syndrome 47 XXY

What's a sex chromosome trisomy

-non disjunction in meiosis 1 or 2 -Robertsonian translocation(with 18 ch and 14 usually 2 out of 12 possibilities of a normal partner mating with RT carrier can have an offspring with trisomy 18 - nondisjunction in mitosis mosaicism 46 XX/XY with 47XX/XY +18

What's the cause of this

Trisomy 18 (Edwards Syndrome) 1-nondisjunction in meiosis 2- robertsonian translocation between 18 and 14 2/12 chance to be trisomy 18 3- post fertilization nondisjunction in mitosis mosaicism 47/46

What's the cause of this condition

45X, Turner syndrome

What's the condition

47XXY Klinefelter Syndrome

What's the condition

47 XY +13 patau syndrome

What's the condition?

Turners syndrome 45X Sex chromosome monosomy The rest of monosomies wether sex or autosomal will be aborted

What's the only monopsony that's compatible with life

Advancing maternal age Family history after 1 baby with Edwards syndrome other baby can get it

What's the risk factors to develop this condition

Death before age 1

What's the survival rate for this patient

Hormonal treatment because decreased testosterone( will help with male sexual characteristics usually given at age 12 testosterone replacement and prevent gynocomastia) and infertility treatment for this issue

What's the treatment for this patient

Supportive Focuses on Life- threatening Conditions(treatment of Heart problems and infections)

What's the treatment for this patient

Edwards syndrome 47 +13

What's this condition?

B- digeorge syndrome/22q11 synrome/ velocardiofacial syndrome Rhyming and parathyroid aplasia due to no development of 3rd and 4th pharyngeal pouches 1-THYMIC APLASIA/HYPOPLASIA No thymus because thymic aplasia/hypoplasia-also recurrent fungal and viral infections due to decreased or deficiency/lack of t cells (lymphopenia in blood test) b lymphocytes are present* 1- HYPOCALCEMIA: bc parathyroid aplasia/hypoplasia- hypoparathyrodism causes hypocalcemia hyperphosphatemia . Hypocalcemia can cause seizures, tetany , chvostek and trousseau sign can be positive 2- DIGEORGE FACIES cleft lip palate, long face small mandible) 3- CONGENITAL HEART DEFECTSBoot shaped heart bc tetrology of fallot( PROV) menonic Pulomary steonsis can cause tet spells(tx squat), RVH on cxr, overriding of aorta on cxr, VSD holosystolic murmur auscultation

You are called urgently to examine a term, 2-hour-old newborn who has had temperature instability, difficulty with feeding, and a sus- pected seizure. He has atypical facies (wide-set eyes, a prominent nose, and a small mandible), a cleft palate, and a holosystolic murmur. Stat laboratory tests and chest radiograph reveal marked hypocalcemia, a boot-shaped heart, and no apparent thymus. Which of the following is the most likely diagnosis? A. Ataxia-telangiectasia B. DIGeorgesyndrome C. Hyper-lgE syndrome D. SCID E. Wiskott-Aldrich syndrome

Hypocalcemia Serum ca dec Hypoparathyrodism Pth dec Hyperphosphatemia inc PO4

À neonate with a cleft palate undergoes a full evaluation. Abnormalities on physical exami- nation include low-set ears and ocular hyper- telorism. Echocardiogram reveals a ventricu- lar septal defect, and of the chest reveals x-ray absence of a thymic shadow. Complete blood cell count with differential reveals lymphopenia. What would be the expected serum calcium, parathyroid hormone, and phosphorus levels for this infant relative to normal?


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