Congenital

disorders present at birth;

includes genetic and developmental disorders

Single Gene Disorders

Autosomal dominant

Autosomal recessive

X-linked

Autosomal Dominant Disorders

- only one mutant allele needed-->either from a parent or a mutation in utero

- males and females are equally affected

- only affected patients transmit the trait; variable expression however

- examples: Marfan syndrom, neurofibromatosis

Neurofibromatosis

Skin nodules and Cafe au lait spots

Eye Changes

Skeletal lesions

Acoustic neuromas...deafness

Marfan Syndrome

- disorder of the connective tissue that affects many organs including the skeleton, jts., eyes, heart and blood vessels

- extremely long limbs

- have arachnodactyly = bones and jts. extremely flexible

- vessels (including aorta) are very elastic--> can lead to aneurysms

Huntington's chorea

Jerky movements, neural deficits

Autosomal recessive disorders

- need one allele from each parent

- parents unaffected generally

- usually present earlier and with more severity

- examples: cystic fibrosis, thalassemia, phenylketonuria, and Tay-Sachs disease

Cystic Fibrosis

- gene is on the long arm of chromosome 7, but there are numerous mutations associated with CF

- thick secretions--> pts. cannot handle Chloride well...perform Sweat Cl test to confirm diagnosis

- may present at birth or years later

- repeated respiratory infections in childhood and respiratory infection as adults

- varied spectrum of presentation

Phenylketonuria

• lacking the aa Alanine(must detect early and correct problem by adding it in diet)
• mandatory part of the newborn screening now

Tay-Sachs disease

• inability to handle proteins in cell
• intracellular inclusions found upon histo exams

X-linked recessive

• mom is a carrier, but only male children will be affected
• females are protected by the 2nd X through lyonization(but on the flip side this mechanism that gets rid of excess genetic material may be bad if the body lyonizes the "good" chromosome with all the normal genes..when this happens (rare) the female carrier will be affected by the disease
• males will pass affected X to their daughters who will be carriers
• Examples: Hemophilia, Fragile X, Duchenne muscular dystrophy, Lesch-Nyhan syndrome