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