The Genetic Workup & Neonatology Flashcards
What guidelines are used to diagnose genetic disease?
- breed and/or sex predisposition
- disease in related animals in pedigree
- characteristic age of onset
- characteristic clinical signs
What 3 prerequisites are used for describing genetic disease?
- characterization of the disease
- knowledge of the mode of inheritance
- accurate diagnosis of affected animals
The following family tree was given for a 16-week-old WHWT with failure to thrive, loss of appetite, abdominal distension, vomiting, PU/PD, and jaundice. CT and necropsy show renal and hepatic cysts. What is the mode of inheritance? What is the likely diagnosis?
- male = square
- female = circle
both sexes of puppies in the litter are affected and parents are normal —> autosomal recessive
autosomal recessive polycystic kidney and liver disease
The following family tree was given for a 12-week-old Pembroke Welsh Corgi with failure to thrive, no palpable LNs, skin lesions, diarrhea, vomiting, ocular and nasal discharge, coughing, and sneezing. Laboratory tests show an absence of lymphocytes, increased neutrophils and eosinophils, and immature lymphoid precursors. Necropsy shows a missing thymus. What is the mode of inheritance? What is the likely diagnosis?
- male = square
- female = circle
- cross = died at birth
only males affected —> X-linked recessive, mothers are carriers
severe combined immunodeficiency (SCID) - chronic infections likely with opportunistic agents, treatment-resistant
A family tree was given for a 1.5-year-old Birman queen who had one litter with a related tom resulting in seemingly healthy kittens born with scabs on feces, greasy skin, and are FeLV/FIV negative. Skin biopsy on the kittens shows no skin adnexa. Necropsy on the kittens shows a lack of thymus. A second litter with the same tom are unaffected. Another litter to a different tom resulted in one affected kitten. What is the mode of inheritance?
- male = square
- female = circle
- diamond = unknown gender
autosomal recessive —> 25% of kittens affected, rest are normal
A family tree was given for Bullmastiff puppies of a first-time mother (and first-time breeder!). There were no complications during the pregnancy and no medications were given. Eight puppies were affected by encephalopathy, crinkled ears, ocular defects, and/or cleft palates. Is it likely this is a genetic disease? What is the most likely organ affected?
unlikely due to history —> inexperienced breeder makes a nutritional defect likely
neural tube affected by hypovitaminosis A - breeder gave further historical information and mentioned that the mother was fed raw liver all throughout pregnancy
What are compound heterozygotes? What is a common disease in cats with similar developments?
two different mutations in the same gene lead to the same genetic disease, but different presentations
mucopolysaccharidosis VI - inherited lysosomal storage disease commonly affecting the joints and bones
- both phenotypes have the same time of onset, but can either cause corneal edema, flat faces, and/or short ears
- can look like it is bred out if BOTH genes are not tested for
What dogs most likely present with genetic disease?
purebreds —> connected to desired traits
- Merle-Merle - severe ocular disease
- Scottish Folds - 2 homozygous positive parents bred together can cause severe cartilaginous and bone defects
What is considered a pediatric dog?
- small breeds = ~6 months
- large breeds = ~1-2 years
(between birth and puberty)
What is neonatology?
in puppies and kittens, the first 2 or 3 weeks of life, characterized by complete dependence on the mother because of incomplete neurological functions, such as audio and visual abilities and proper spinal reflexes
- cannot survive on their own!
What are common clinical signs associated with problems in neonates?
- no weight gain (“fall off the curve”)
- apathy
- vocalization (more common in puppies)
- rejection by dam
- hypothermia
- dehydration
NON-SPECIFIC
What is the average weight of kittens at birth? What weight gain is expected?
100 g
- 100 g per week
- 1 lb per month
- LINEAR
(feral = less weight gain)
In what 2 ways is the weight of puppies at birth different compared to kittens? What gain is expected?
- highly breed-specific
- sigmoid growth
should double birth weight by 7-10 days, followed by 5-10% daily increase (weekly gain ranges from 150g-1.25kg depending on breed)
What are important aspects of the physical exams in neonates?
- body temperature - requires a thermometer that can reach down to 85 degrees for accuracy
- MM character
- hair coat
- abdominal skin
- symmetry and conformation
- external genitalia
- tail
What is occurring in these neonates?
TOP = cleft palate
BOTTOM = ectodermal dysplasia
What is occurring in these neonates?
two puppies to the left have domed heads and short snouts, indicative of hydrocephalus
(puppy on the right is normal)
What is the best way to classify hydration in neonates? Why?
MM palpation and character —> should not be tacky, should be pink
skin turgor is not reliable - naturally elastic and extra skin can look like turgor
What is likely happening in this neonate?
porphyria —> unable to convert porphyrin in heme
What is the normal structure of the abdominal skin in neonates? Why is it closely observed on physical exams?
close to hairless - will grow more with age
easy to observe cyanosis or sepsis (dark red/purple)
What is an XX sexual reversal?
male dog born with female chromosomes (XX), resulting in abnormal penis/prepuce or infertility
- dog on the left has a more caudal, “wimpy” prepuce
What is hypospadias?
failure of fusion of urogenital folds during fetal development, causing incomplete closure of the penile urethra and the urethral meatus to open on the ventral surface of the penile shaft proximal to its normal location
- penis commonly dries out
How does spina bifida affect neonates?
no tone in back legs and tail
How does the circulatory system develop in neonates? What 3 effects does this have?
pO2 rises to 100 mmHg by day 3
- dilates pulmonary vessels
- closes ductus arteriosus
- corrects acidosis
What 3 heart/circulatory levels are most commonly lower? Higher?
LOWER - BP, SV, peripheral vascular resistance
HIGHER - HR, CO, central venous pressure
What are four normal differences in neonatal blood cell counts?
- physiologic anemia - PCV remains the same as mother, but drops quickly
- high lymphocytes - can be confused with leukemia
- high reticulocytes and nRBCs
- high granulocytes - no longer in sterile environment
How long does it take for proper thyroid develop to happen in neonates?
high in neonates, but by 12 weeks adult values should be reached
- kittens are not the same as puppies
- no differences between genders or breeds
