USMLE Step 1: Biochemistry & other

GGT (gamma glutamyl transpeptidase)

• caused by bacteria, Tropheryma whipplei
• rare, infectious systemic disease
• causes primarily malabsorption
• common symptoms:
  • weight loss
  • diarrhoea
  • joint pain
  • arthritis
• darkening of the skin occurs in half of the patients

= are functionally asplenic –> increased risk for infection by encapsulated organisms (St. pneumoniae, Hib)

• nonspecific reactive change of glial cells in response to damage to the cns
• first response to injury: migration of macrophages and local microglia to the injury site = microgliosis (within hours)
• second: oligodendrocyte precursor cells are also recruited to the site and may contribute to remyelination (after 3–5 days) 
• Third and final: astrogliosis, the proliferation of surrounding astrocytes, which are the main constituents of the glial scar.

mediastinal mass that can cause respiratory symptoms, dysphagia or SVCS

ANCA associated rapidly progressive glomerulonephritis (RPGN)

• calcified cystic tumor
• remnant of Rathke's pouch
• causes headaches, growth failure, bitemporal hemianopsia

• causes nerve problems
• signs
  • neuromuscular problems: e.g. spinocerebellar ataxia, myopathies
  • neurological problems: dysarthria, absence of deep tendon reflexes, loss of vibratory sensation and proprioception, positive Babinski sign
  • anemia
  • retinopathy
  • impairment of the immune response

Deletion of long arm chrom. 22

Metaphase of meiosis II

neural tube defects

• major constituents of surfactant
• increase sharply after 30 weeks of gestation
• in amniotic fluid

• failure of proper fusion of the maxillary prominence with the intermaxillary segment

• when palatine shelves of the maxillary prominence fail to properly fuse with one another or with the primary palate

• t(14;18) –> Bcl-2 overexpression

1. APP (chrom. 21)
2. presenilin 1
3. presenilin 2

apolipoprotein E4 genotype

bilateral –> associated with tuberous sclerosis

indirect

impairs posttranslational processing of CFTR

failure of obliteration involving the omphalomesenteric duct –> obliterates normally during the 7^th week

• are outgrowths of the duodenum
• join together to form the pancreas
• ventral bud forms the major pancreatic duct
• dorsal bud forms the accessory pancreatic duct

• micrognathia
• micropthalmia
• overlapping fingers
• rocker-bottom feet

• absence of GnRH secretory neurons in the hypothalamus
• clinical findings:
  • central hypogonadism
  • anosmia

delayed puberty

• often occurs secondary to nondisjunction during maternal meiosis
• clinical findings:
  • cleft lip & palate
  • polydactyly, rocker-bottom fett
  • holoprosencephaly

AML (M3)

• leakage of urine through the umbilicus
• 4 anatomical causes:
  1. urachus cyst
  2. urachus fistula
  3. urachus diverticulum
  4. urachus sinus

• autosomal recessive
• mutated FXN gene on chrom. 9 with amplified GAA triplets
• associated with:
  • hypertrophic cardiomyopathy
  • diabetes mellitus
  • kyphoscoliosis
  • foot deformities

1. can produce a very tender, small red-blue lesion under the nail bed
2. originate from the modified smooth muscle cells that control the thermoregulatory functions of dermal glomus bodies

= autoimmune

= most common benign liver tumor

Biopsy is contraindicated –> fatal hemorrhage

• anaerobic bacteria
• normally found in the oral cavity
• most frequent cause of lung abscess
• RF for lung abscess: conditions that increase aspiration risk –> alcoholism, drug abuse, seizure disorders, stroke, dementia

1. rupture of saccular aneurysm or arteriovenous malformation
2. severe vasospasm after initial insult –> nimodipine can prevent vasospasm

1. erythema infectiosum
2. arthritis