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Dermatology Test 2

All of the following are considered type II immune reactions, except:

ExplanationA type II immune reaction is characterized by the interaction between an antibody and an antigen, with consequent downstream effects. Graves disease is caused by the binding of anti-TSH antibodies to the TSH receptor, with consequent hyperstimulation of the thyroid, leading to gland enlargement and hyperthyroidism. Myasthenia gravis is caused by antibodies to the acetylcholine receptor at the postsynaptic neuromuscular junction, with consequent neuromuscular weakness. Pernicious anemia can be caused by autoantibodies to either parietal cells or to intrinsic factor itself, both resulting in decreased levels of intrinsic factor and vitamin B12 deficiency. Autoimmune hemolytic anemia is caused by antibodies that result in erythrocyte destruction and hemolysis. While antibodies may be involved in the pathogenesis of graft-versus-host disease, most manifestations of the disease are caused by T-lymphocytes from the graft targeting host tissues, with prominent manifestations in the skin, the gut, and the liver

Dermatology Test 2

A 6-month-old boy presents to the emergency department with fever and tachypnea, and is found to be in diabetic ketoacidosis. He has a history of intractable watery diarrhea and a gradually worsening eczematous dermatitis. His older brother had many of the same conditions, along with hypothyroidism, and died in early childhood. This likely represents a defect in _____, a key signaling molecule in _____

ExplanationThe patient likely has IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) syndrome, characterized by early onset of Type 1 diabetes, chronic diarrhea, and an eczematous dermatitis that often proves refractory to common treatments and can continue to erythroderma. The disease is often rapidly progressive, with diverse described manifestations, including sepsis, hypogammaglobulinemia, and arthritis, and often results in death within the first years of life. These patients have defects in FoxP3 and have dysfunctional Treg cells which may switch to an inflammatory TH17 phenotype.

Dermatology Test 2

A patient presents with recurrent MRSA abscesses, thrush, and chronic lung infections. Laboratory examination reveals extremely elevated levels of IgE. Hyper IgE syndrome in DOCK8 deficiency can be distinguished from that occurring in STAT3 deficiency by:

ExplanationHyper IgE syndrome is characterized by patients with recurrent MRSA abscesses, thrush, and chronic lung infections leading to bronchiectasis and pneumatoceles. Hyper IgE syndrome can be caused by both STAT3 mutations and DOCK8 mutations, but patients with STAT3 mutations tend to have “coarse,” dysmorphic facies and retained deciduous teeth, while patients with DOCK8 mutations tend to have viral infections and severe food allergies.

Dermatology Test 2

A patient presents with recurrent MRSA abscesses, thrush, and chronic lung infections. Physical examination reveals facial dysmorphism and retained deciduous teeth. The most likely mutation is in_____.

Dermatology Test 2

CTLA-4 binds to ____, and serves to ____T-cell activation. _____binds to and inhibits CTLA-4.

ExplanationCTLA-4 is a regulatory molecule expressed on T-cells that binds to B7 on antigen-presenting cells and downregulates T-cell activation. Ipilimumab is a monoclonal antibody that inhibits CTLA-4, inhibiting the inhibitor and increasing T-cell activation. Ipilimumab has been shown to have modest survival benefits in metastatic melanoma.

Dermatology Test 2

Local skin necrosis following the use of soft-tissue filler for the correction of dermal rhytides occurs most frequently at which of the following sites?

ExplanationLocal skin necrosis most commonly occurs after injection of dermal fillers in the glabella, but may occur in any location. Necrosis is thought to occur either by direct injection of filler into a vessel that supplies the area or from compression of vessels in the area by edema or the bulk of excessive filler.

Dermatology Test 2

Treatment with which of the following lasers most commonly results in purpura?

ExplanationThe pulsed dye laser is frequently associated with purpura formation, particularly when used at shorter pulse durations.

Dermatology Test 2

Which of the following lasers operates in the red portion of the electromagnetic spectrum?

ExplanationThe alexandrite laser emits red light at a wavelength of 755 nm. The pulsed dye laser emits yellow light at 585 to 595 nm. The KTP laser emits green light at 532 nm. Neither the Nd:YAG nor carbon dioxide lasers emit light in the visible spectrum.

Dermatology Test 2

Neutralization of which of the following chemical peels is important to prevent excess penetration?

ExplanationGlycolic acid peeling agents do not induce enough coagulation of skin proteins and therefore cannot neutralize themselves. They must be neutralized using copious amounts of water or a weak buffer agent such as sodium bicarbonate.

Dermatology Test 2

What does Botox cleave?

ExplanationSeven botulinum toxin serotypes (A–G) bind to different sites on the motor nerve terminal and within the motor neuron. Botox is botulinum toxin type A, and Myobloc is botulinum toxin type B. Synaptosomal-associated protein (SNAP-25) is cleaved by serotypes A and E. Vesicle-associated membrane protein (VAMP, synaptobrevin) is cleaved by serotypes B, D, F, and G. Syntaxin 1 is cleaved by serotype C1. Cleavage of these proteins prevents exocytosis of acetylcholine into the synapse between the motor neuron and the skeletal muscle cell.

Dermatology Test 2

What neurotransmitter is blocked by botulinum toxin?

ExplanationNeurotransmitters are chemicals used to signal between a neuron and another cell. They are present in the presynaptic element, bind to postsynaptic receptors, and must be in sufficient quantity to affect the postsynaptic cell. Botulinum toxin blocks neurotransmitter release at peripheral cholinergic nerve terminals. Epinephrine, dopamine, norepinephrine, gamma aminobutyric acid, melatonin, serotonin and glutamic acid are other neurotransmitters.

Dermatology Test 2

Uniform white frost with pink showing through correlates with what depth of injury after a trichloroacetic acid peel?

ExplanationAfter defatting the skin, chemical peeling agents are applied to the skin. Skin keratin begins to agglutinate. Depth of peel can be correlated with the intensity of the frost: no frost (stratum corneum), irregular light frost (superficial epidermis), and uniform white frost with pink showing through (full thickness epidermis).

Dermatology Test 2

Endovascular venous ablation techniques using laser or radio frequency can be most safely applied to which of the following veins?

ExplanationEndovenous laser ablation (ELA) and radio-frequency ablation (RFA) have replaced stripping and ligation as the technique of choice for elimination of saphenous vein reflux. The other veins listed all fall within the deep venous system of the lower extremity.

Dermatology Test 2

Which of the following wavelengths penetrates most deeply into the skin?

ExplanationIn general, depth of penetration increases with wavelength, however this is not true for traditional ablative lasers such as the 10,600 nm carbon dioxide laser. The longer infrared laser wavelengths are absorbed efficiently by water in the superficial dermis such that penetration is limited

Dermatology Test 2

Which of the following chemical peel agents is most likely to cause cardiac arrhythmias?

ExplanationCardiac arrhythmias are a potential complication in phenol face peeling. All patients who undergo phenol peels should have cardiac monitoring and careful attention to their fluid status and hydration. Cardiac arrhythmias typically develop during phenol peels when the peeling solution is applied too rapidly resulting in systemic accumulation of excess phenol. To help avoid this problem, individual facial segments (cheeks, forehead, perioral, periorbital, and nose should be treated with at least a 15 minute time delay between them.

Dermatology Test 2

Which of the following wavelengths is most appropriate for ablative laser skin resurfacing?

ExplanationTraditional ablative laser skin resurfacing is most commonly accomplished with the 2,940 nm Erbium:YAG and 10,600 nm carbon dioxide lasers.

Dermatology Test 2

Which of these patients do not require prophylactic antibiotics preoperatively to prevent endocarditis?

ExplanationMitral valve regurgitation was once an indication for prophylactic antibiotics to prevent endocarditis. Without other risk factors, mitral regurgitation no longer requires preoperative prophylactic antibiotics

Dermatology Test 2

Which of these interpolation flaps is not an axial flap?

ExplanationThe cheek-to-nose staged flap is NOT an axial flap. It receives vascular supply from branches of the angular artery but the angular artery itself is not in the pedicle. The paramedian forehead flap’s pedicle is the supratrochlear artery, the lip-switch and the Abbe Estlander flaps’ pedicles are from either the inferior labial artery or superior labial artery.

Dermatology Test 2

Which absorbable suture has less tissue reactivity?

ExplanationPolyglactin. Suture characteristics include tensile strength, knot strength, configuration, elasticity, memory or suture stiffness, plasticity, and pliability. Suture reactivity is another characteristic defined as the amount of inflammatory response that is elicited, which is dependent on the material from which it is made. Synthetic sutures are made from synthetic collagen derived from polymers and are broken down by hydrolysis as opposed to enzymatic degradation in natural sutures, causing less tissue reaction. In contrast, natural sutures are made from natural materials such as collagen derived from the gastrointestinal tract of animals, woven cotton, raw silk, linen, or steel. Of the answer choices listed, polyglactin 910 and gut suture are absorbable suture made from synthetic and natural materials, respectively

Dermatology Test 2

Which nonabsorbable suture has more tissue reactivity?

ExplanationSilk. Suture characteristics include tensile strength, knot strength, configuration, elasticity, memory or suture stiffness, plasticity, and pliability. Suture reactivity is another characteristic defined as the amount of inflammatory response that is elicited, which is dependent on the material from which it is made. Synthetic sutures are made from synthetic collagen derived from polymers and are broken down by hydrolysis as opposed to enzymatic degradation in natural sutures, causing less tissue reaction. In contrast, natural sutures are made from natural materials such as collagen derived from the gastrointestinal tract of animals, woven cotton, raw silk, linen, or steel. Of the answer choices listed, polypropylene and silk are nonabsorbable suture made from synthetic and natural materials, respectively

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