Proteoglycans are extracellular matrix molecules that have a central protein core or backbone structure with covalently attached glycosaminoglycans. Proteoglycans, cartilage, and water are the main constituents of human cartilage.
In osteoarthritis, the breakdown of articular cartilage caused by chronic repetitive use and inflammation results in the decreased synthesis of proteoglycans by the chondrocytes. The loss of this component of cartilage is reflected at the macroscopic level by cartilage degradation and bone-bone contact osteoarthritic degenerative joint disease. Decreased proteoglycan secretion is expected on arthrocentesis, synovial fluid may show few leukocytes, but otherwise will be without evidence of acute inflammation or infection.
The patient's enzyme needs more substrate to achieve the same effect as the normal enzyme.
The Km is the substrate concentration at which the enzyme achieves 50% maximal concentration.
More substrate is needed in the patient to reach the 50% maximal velocity than is needed in the normal patient so it must be that there is a mutation in the enzyme that increases Km.
The Bartholin glands, or the greater vestibular glands, are a pair of glands on either side of the posterior vaginal orifice that secretes a lubricating fluid through two small ducts into the vestibule. When one of these glands becomes blocked, a cyst may occur.
The infection is generally polymicrobial, but anaerobes such as Bacteriodes fragilis, Clostridium perfringens, Peptostreptococcus, and Fusobacterium are key pathogens.
Cryptosporidiosis presents with severe watery diarrhea in immunocompromised patients; it is diagnosed by microscopy of the stool showing red-pink oocysts on the acid-fast stain.
The patient with HIV infection and 10 days of watery diarrhea and abdominal cramps has been infected with Cryptosporidium, an intracellular parasite that causes a severe GI illness in an immunocompromised patient.
The peripheral blood smear shows a schizont form of the parasite, although any malarial stage (gametocyte, schizont, trophozoite, or ring) can be seen on a smear and is diagnostic of infection. CHLOROQUINE effectively eradicates circulating forms if there is no resistance but has NO EFFECT ON THE HYPNOZOITE EXOERYTHROCYTIC forms of P Vivax and P ovale. Addition of PRIMAQUINE effectively treats these liver forms and prevents relapsing infection.
Pulsus paradoxus refers to the abnormal variation of systolic blood pressure between inspiration and expiration (greater than 100 mm Hg). This presents as jugular venous distension sometimes and is often seen in conditions that restrict expansion of the heart, such as cardiac tamponade.
Maternal glucose crosses the placenta while insulin does not (remember that HPL services the baby by shunting the mother's glucose to the baby by conferring insulin resistance to the mom). In response to hyperglycemia in the mom, the fetal pancreatic islet cells increase the production of insulin. If the source of glucose is quickly removed, such as after delivery, the infant has a high risk of developing hypoglycemia, which can lead to convulsions and death.
See this question in NBME 27 asking about what a 5-alpha-reductase deficiency would look like.
The SRY gene is located on the Y chromosome and is responsible for producing the testis-determining factors, which results in male gonadal differentiation. In testis development, hormones secreted by Sertoli cells (MIF Macrophage Inhibiting Factor) and Leydig cells (testosterone and DHT) promote the development of male internal and external genitalia and suppress the development of female structures. SRY gene translocation can occur during recombination in which the SRY gene on the Y chromosome becomes part of the X chromosome, leading to an XX embryo developing male characteristics.
An intensely eosinophilic globule in the liver is a Councilman body that is indicative of an underlying hepatic disease, viral Hepatitis (usually Hepatitis A), or Yellow fever. This represents a hepatocyte undergoing APOPTOSIS.
Recall that Yello Fever is caused by flavivirus/arbovirus transmitted by the Aedes mosquito causing black vomitus, jaundiced eyes, and the Councilman bodies (intensely eosinophilic apoptotic globules in the liver).
To also answer this question, one had to know that apoptosis caused by activation of the mitochondrial intrinsic pathway is triggered by cellular damage such as radiation, oxidative damage, ischemia, or toxin exposure and leads to release of cytochrome C from mitochondria. Cytochrome C in turn leads to the activation of caspase enzymes. Viral hepatitis primarily leads to apoptosis through the extrinsic rather than the intrinsic pathway.
Morbilliform skin rash is HIGH-YIELD for a drug reaction, the most severe being Drug reaction with eosinophilia and system symptoms (DRESS). It is associated with the use of allopurinol, anticonvulsants, antibiotics like TMP-SMX, and sulfa drugs. This is a potentially fatal delayed hypersensitivity reaction.
It is also related to a severe rash Stevens-Johnson syndrome or Toxic epidermal necrolysis which is also caused by anti-epileptic drugs (especially lamotrigine), allopurinol, sulfa drugs, and penicillin.
See here in FA 2020 for a list of extrahepatic manifestations in HepC and HepB. Importantly HepC can induce essential mixed cryoglobulinemia. It presents with palpable purpura in association with arthralgia and peripheral neuropathies caused by immune-complex type III hypersensitivity mediated vasculitis.
The triad is weakness, arthralgia, and palpable purpura. Keep in mind peripheral neuropathy, hematuria, and hepatosplenomegaly and most importantly, Hepatitis C.
This image is clinically extremely similar to the image for Fibromuscular dysplasia in FA 2020 on pp300.
90% of hypertension is 1° (essential) and related toCO orTPR. The remaining 10% is mostly 2° to renal/renovascular diseases such as fibromuscular dysplasia (characteristic “string of beads” appearance of the renal artery, usually seen in women of child-bearing age) and atherosclerotic renal artery stenosis or to 1° hyperaldosteronism.
This question should be easy but if you didn't go through all the options, or if you're like me and tunnel-vision on seemingly right options, then you can miss "gimme" points on a question like this. We know that DNA plasmids in bacterial are circular and don't really have a terminal end or beginning but rather have DNA synthesis sites where DNA polymerases can attach to begin replication.
See this question in block 1 about GVHD.
See also these tables on transplant rejection pathologies from FA 2020.
Chronic allograft rejection of a transplanted organ occurs over months to years (the question was in the timeline of weeks). It is secondary to a CD4+ T lymphocyte response against donor peptides such as MHC. T cell activation leads to cytokine production and humoral and cellular hypersensitivity reactions (type II and IV). When you think Chronic rejection, you should be thinking VESSELS because this often leads to vascular arteriosclerosis and smooth muscle proliferation with parenchymal fibrosis and atrophy.
With acute rejection, you should be thinking of INFILTRATION, that is T-lymphocytes in the vasculature of the tubules and arterial walls leading to endothelitis. The primary histologic changes include interstitial infiltration with lymphocytic cells, in addition to the obliteration of the tubular basement membranes (as in this question with a kidney transplant).
See pages from FA 2020 and other resources.
The moment we see HepB seropositivity, cutaneous eruptions, and different stages of TRANSMURAL INFLAMMATION WITH FIBRINOID NECROSIS, we should be thinking Polyarteritis nodosa (PAN). It is treated with corticosteroids and cyclophosphamide.
This patient had segmental transmural necrotizing arteritis making PAN the best answer.
Recall that for Giant cell arteritis or temporal arteritis, one would see a headache, temporal tenderness, jaw claudication, and fever.
Antiphospholipid syndrome is diagnosed based on recurrent venous thromboses (hypercoagulability), frequent miscarriages, thrombocytopenia, and a false-positive rapid plasma reagin test. It is associated with clinical criteria including a history of thrombosis (arterial or venous) or spontaneous abortion along with laboratory findings of lupus anticoagulant, anticardiolipin, anti-β2 glycoprotein I antibodies.