Red flags in skin conditions — MCQs

10 questions

A 52-year-old woman with type 2 diabetes mellitus comes to the physician because of a 2-day history of blisters on her forearms and pain during sexual intercourse. Her only medications are metformin and glyburide. Examination reveals multiple, flaccid blisters on the volar surface of the forearms and ulcers on the buccal, gingival, and vulvar mucosa. The epidermis on the forearm separates when the skin is lightly stroked. Which of the following is the most likely diagnosis?

A 52-year-old Caucasian man presents to the clinic for evaluation of a mole on his back that he finds concerning. He states that his wife noticed the lesion and believes that it has been getting larger. On inspection, the lesion is 10 mm in diameter with irregular borders. A biopsy is performed. Pathology reveals abnormal melanocytes forming nests at the dermo-epidermal junction and discohesive cell growth into the epidermis. What is the most likely diagnosis?

A 4-year-old boy is presented to the clinic by his mother due to a peeling erythematous rash on his face, back, and buttocks which started this morning. Two days ago, the patient’s mother says his skin was extremely tender and within 24 hours progressed to desquamation. She also says that, for the past few weeks, he was very irritable and cried more than usual during diaper changes. The patient is up to date on his vaccinations and has been meeting all developmental milestones. No significant family history. On physical examination, the temperature is 38.4°C (101.1°F) and the pulse is 70/min. The epidermis separates from the dermis by gentle lateral stroking of the skin. Systemic antibiotics are prescribed, and adequate fluid replacement is provided. Which of the following microorganisms most likely caused this patient’s condition?

A 4-year-old boy is brought to the emergency department by his mother with a rash on his trunk, malaise, and fever with spikes up to 38.5°C (101.3°F) for the past 2 weeks. The patient's mother says she tried giving him Tylenol with little improvement. Past medical history includes a spontaneous vaginal delivery at full term. The patient's vaccines are up-to-date and he has met all developmental milestones. On physical examination, his lips are cracking, and he has painful cervical lymphadenopathy. The rash is morbilliform and involves his trunk, palms, and the soles of his feet. There is fine desquamation of the skin of the perianal region. Which of the following anatomical structures is most important to screen for possible complications in this patient?

A 52-year-old woman sees you in your office with a complaint of new-onset headaches over the past few weeks. On exam, you find a 2 x 2 cm dark, irregularly shaped, pigmented lesion on her back. She is concerned because her father recently passed away from skin cancer. What tissue type most directly gives rise to the lesion this patient is experiencing?

A 45-year-old woman presents to the clinic with a variety of complaints on different areas of her body, including telangiectasias on both the upper and lower extremities, bluish discoloration of the fingertips when exposed to cold, and burning midsternal chest pain. She is a tobacco smoker and works as a school teacher. After evaluation, an anti-centromere antibody test is ordered, and returns with an elevated titer. Which of the following symptoms are least likely to be seen in this patient's condition?

A 49-year-old woman with a history of intravenous drug use comes to the physician because of a 6-month history of fatigue, joint pain, and episodic, painful discoloration in her fingers when exposed to cold weather. She takes no medications. She has smoked one pack of cigarettes daily for the past 22 years. She appears tired. Physical examination shows palpable, nonblanching purpura over the hands and feet. Neurological examination shows weakness and decreased sensation in all extremities. Serum studies show: Alanine aminotransferase 78 U/L Aspartate aminotransferase 90 U/L Urea nitrogen 18 mg/dL Creatinine 1.5 mg/dL Which of the following processes is the most likely explanation for this patient's current condition?

A 48-year-old male presents to his primary physician with the chief complaints of fever, abdominal pain, weight loss, muscle weakness, and numbness in his lower extremities. UA is normal. A biopsy of the sural nerve reveals transmural inflammation and fibrinoid necrosis of small and medium arteries. Chart review reveals a remote history of cigarette smoking as a teenager and Hepatitis B seropositivity. What is the most likely diagnosis?

A 67-year-old man presents to the emergency department with increased fatigue. He states that he has been feeling very tired lately but today lost consciousness while walking up the stairs. He reports mild abdominal distension/discomfort, weight loss, a persistent cough, and multiple episodes of waking up drenched in sweat in the middle of the night. The patient does not see a primary care physician but admits to smoking 2 to 3 packs of cigarettes per day and drinking 1 to 3 alcoholic beverages per day. He recently traveled to Taiwan and Nicaragua. His temperature is 99.5°F (37.5°C), blood pressure is 177/98 mmHg, pulse is 100/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you note a fatigued appearing elderly man who is well-groomed. Cardiopulmonary exam reveals mild expiratory wheezes. Abdominal exam is notable for a non-pulsatile mass in the left upper quadrant. Laboratory values are ordered as seen below. Hemoglobin: 12 g/dL Hematocrit: 36% Leukocyte count: 105,500/mm^3 Platelet count: 197,000/mm^3 Serum: Na+: 139 mEq/L Cl-: 100 mEq/L K+: 4.3 mEq/L HCO3-: 25 mEq/L BUN: 20 mg/dL Glucose: 92 mg/dL Creatinine: 1.4 mg/dL Ca2+: 10.2 mg/dL Leukocyte alkaline phosphatase score: 25 (range 20 - 100) AST: 12 U/L ALT: 17 U/L Which of the following is the most likely diagnosis?

Q10

A 24-year-old man presents to the clinic with the complaint of a new rash. The lesions are not bothersome, but he is worried as he has never seen anything like this on his body. Upon further questioning the patient states has been generally healthy except for a one time "horrible" flu-like episode two months ago in June. He has since gotten better. On physical exam the following rash is observed (Figure 1). What is the cause of this patient's rash?

Red flags in skin conditions US Medical PG Practice Questions and MCQs

Question 1: A 52-year-old woman with type 2 diabetes mellitus comes to the physician because of a 2-day history of blisters on her forearms and pain during sexual intercourse. Her only medications are metformin and glyburide. Examination reveals multiple, flaccid blisters on the volar surface of the forearms and ulcers on the buccal, gingival, and vulvar mucosa. The epidermis on the forearm separates when the skin is lightly stroked. Which of the following is the most likely diagnosis?

A. Behcet disease
B. Pemphigus vulgaris (Correct Answer)
C. Toxic epidermal necrolysis
D. Dermatitis herpetiformis
E. Lichen planus

Explanation: ***Pemphigus vulgaris*** - The presence of **flaccid blisters** on the skin, **oral and vulvar mucosal ulcers**, and a **positive Nikolsky sign** (epidermal separation with light stroking) are classic features of **pemphigus vulgaris**. - This autoimmune blistering disease is characterized by antibodies against **desmoglein 1 and 3**, leading to acantholysis within the epidermis. *Behcet disease* - Behcet disease is characterized by recurrent **oral ulcers**, genital ulcers, and uveitis, but it typically presents with deeper, painful ulcers rather than **flaccid blisters** and does not involve a positive Nikolsky sign. - Skin lesions in Behcet's disease often include **erythema nodosum** or papulopustular lesions, not thin-walled blisters. *Toxic epidermal necrolysis* - **Toxic epidermal necrolysis (TEN)** is a severe, life-threatening drug-induced reaction characterized by widespread **epidermal detachment** (often >30% body surface area) and mucosal involvement, but it typically presents with widespread, confluent erythema followed by sheet-like epidermal peeling, not distinct flaccid blisters. - The onset is usually acute following drug exposure, and patients are often critically ill with systemic symptoms; while this patient has blisters, the description of "multiple, flaccid blisters" and pain during intercourse points away from the acute, widespread, drug-induced skin necrosis of TEN. *Dermatitis herpetiformis* - **Dermatitis herpetiformis** typically presents with intensely **pruritic, erythematous papules and vesicles** symmetrically distributed on extensor surfaces, and it is strongly associated with **celiac disease**. - It does not usually cause **flaccid blisters** or a positive Nikolsky sign, and oral lesions are uncommon. *Lichen planus* - **Lichen planus** is characterized by **pruritic, purple, polygonal, planar papules and plaques** with fine white lines (Wickham striae) and can affect skin, hair, nails, and mucous membranes. - While oral lesions (lacy white networks) and vulvar involvement can occur, it typically does not present with **flaccid blisters** or a positive Nikolsky sign.

Question 2: A 52-year-old Caucasian man presents to the clinic for evaluation of a mole on his back that he finds concerning. He states that his wife noticed the lesion and believes that it has been getting larger. On inspection, the lesion is 10 mm in diameter with irregular borders. A biopsy is performed. Pathology reveals abnormal melanocytes forming nests at the dermo-epidermal junction and discohesive cell growth into the epidermis. What is the most likely diagnosis?

A. Desmoplastic melanoma
B. Lentigo maligna melanoma
C. Superficial spreading melanoma (Correct Answer)
D. Nodular melanoma
E. Acral lentiginous melanoma

Explanation: ***Superficial spreading melanoma*** - This is the **most common type of melanoma**, accounting for 70% of cases, and typically presents with a **radial growth phase** showing irregular borders and enlarging size. - Histopathology revealing **nests of abnormal melanocytes at the dermo-epidermal junction** and **discohesive cell growth into the epidermis** (pagetoid spread) is characteristic of superficial spreading melanoma. *Desmoplastic melanoma* - Characterized by **fibrous stroma** and often **neural invasion**, with a less pigmented appearance, which is not described. - Typically presents as a firm, often amelanotic nodule, and can be more aggressive. *Lentigo maligna melanoma* - Primarily found in **chronically sun-damaged areas** of the elderly, often on the face, and begins as a flat, tan-brown macule that slowly enlarges. - Histologically, it shows **atypical melanocytes along the basal layer** of a thinned epidermis, not necessarily forming nests or extensive discohesive growth into the epidermis early on. *Nodular melanoma* - This type of melanoma has a **vertical growth phase from the outset**, appearing as a rapidly growing, dark, elevated lesion without a significant preceding radial growth phase. - Histologically, it involves a substantial dermal component with **minimal or absent intraepidermal radial growth**. *Acral lentiginous melanoma* - Occurs on the **palms, soles, or under the nails (subungual)**, and is less associated with sun exposure, often presenting as a dark, spreading lesion. - Its histological features involve **lentiginous proliferation of atypical melanocytes** along the dermo-epidermal junction with spread into the rete ridges in an acral distribution.

Question 3: A 4-year-old boy is presented to the clinic by his mother due to a peeling erythematous rash on his face, back, and buttocks which started this morning. Two days ago, the patient’s mother says his skin was extremely tender and within 24 hours progressed to desquamation. She also says that, for the past few weeks, he was very irritable and cried more than usual during diaper changes. The patient is up to date on his vaccinations and has been meeting all developmental milestones. No significant family history. On physical examination, the temperature is 38.4°C (101.1°F) and the pulse is 70/min. The epidermis separates from the dermis by gentle lateral stroking of the skin. Systemic antibiotics are prescribed, and adequate fluid replacement is provided. Which of the following microorganisms most likely caused this patient’s condition?

A. Clostridium sp.
B. Staphylococcus aureus (Correct Answer)
C. Neisseria meningitidis
D. Bacillus anthracis
E. Streptococcus sp.

Explanation: ***Staphylococcus aureus*** - The presentation of a **peeling erythematous rash** that started this morning following a period of **extremely tender skin** and **progression to desquamation (Nikolsky's sign)** is highly characteristic of **Staphylococcal Scalded Skin Syndrome (SSSS)**. - **Staphylococcus aureus** produces **exfoliative toxins A and B** that cleave desmoglein-1 in the stratum granulosum, leading to intraepidermal cleavage and superficial skin peeling. *Clostridium sp.* - Clostridium species are primarily known for causing diseases like **gas gangrene** and **tetanus**, which involve deep tissue infections and neurological symptoms, not superficial skin peeling. - They are often associated with **severe wound infections** or **food poisoning**, with different clinical manifestations. *Neisseria meningitidis* - Neisseria meningitidis is a common cause of **meningitis** and **meningococcemia**, which typically presents with a **petechial or purpuric rash** that does not involve peeling or desquamation. - Symptoms would primarily include fever, headache, stiff neck, and rapid clinical deterioration. *Bacillus anthracis* - Bacillus anthracis causes **anthrax**, with cutaneous anthrax presenting as a **papule progressing to a painless ulcer with a black eschar** (black, necrotic center), without generalized peeling or tenderness. - This is clearly distinct from the diffuse erythematous and peeling rash described. *Streptococcus sp.* - While Streptococcus pyogenes can cause **scarlet fever** with a diffuse erythematous rash and subsequent desquamation, the rash in scarlet fever is typically **sandpaper-like** and the desquamation occurs later, usually in sheets on hands and feet. - **Toxic Shock Syndrome (TSS)** due to Streptococcus pyogenes can cause a diffuse rash and desquamation, but typically presents with more severe systemic illness and hypotension, and the characteristic tenderness and rapid progression to widespread peeling as seen in SSSS are less typical for Streptococcus.

Question 4: A 4-year-old boy is brought to the emergency department by his mother with a rash on his trunk, malaise, and fever with spikes up to 38.5°C (101.3°F) for the past 2 weeks. The patient's mother says she tried giving him Tylenol with little improvement. Past medical history includes a spontaneous vaginal delivery at full term. The patient's vaccines are up-to-date and he has met all developmental milestones. On physical examination, his lips are cracking, and he has painful cervical lymphadenopathy. The rash is morbilliform and involves his trunk, palms, and the soles of his feet. There is fine desquamation of the skin of the perianal region. Which of the following anatomical structures is most important to screen for possible complications in this patient?

A. Mitral valve
B. Kidneys
C. Gallbladder
D. Coronary artery (Correct Answer)
E. Pylorus

Explanation: ***Coronary artery*** - The constellation of symptoms, including prolonged fever, rash on trunk, palms, and soles, cracked lips, cervical lymphadenopathy, and perianal desquamation, is highly indicative of **Kawasaki disease**. - **Coronary artery aneurysms** are the most serious complication of Kawasaki disease, occurring in 15-25% of untreated children, necessitating close monitoring and screening. *Mitral valve* - While other forms of vasculitis or rheumatic fever can affect heart valves, **mitral valve** involvement is not a primary or characteristic complication of Kawasaki disease. - The main cardiac concern in Kawasaki disease is direct arterial inflammation, not valvular dysfunction. *Kidneys* - **Renal involvement**, such as acute kidney injury, is not a typical or prominent feature of Kawasaki disease. - Kawasaki disease primarily targets medium-sized muscular arteries throughout the body, with a predilection for the coronary arteries. *Gallbladder* - **Hydrops of the gallbladder** can occur in Kawasaki disease, leading to acute cholecystitis-like symptoms, but it is generally a self-limiting complication. - While it's a potential finding, it is not as life-threatening or essential to screen for as coronary artery complications. *Pylorus* - There is no direct association between Kawasaki disease and primary involvement or complications of the **pylorus**. - Gastrointestinal symptoms can occur, but these are typically non-specific and do not involve anatomical changes to the pylorus.

Question 5: A 52-year-old woman sees you in your office with a complaint of new-onset headaches over the past few weeks. On exam, you find a 2 x 2 cm dark, irregularly shaped, pigmented lesion on her back. She is concerned because her father recently passed away from skin cancer. What tissue type most directly gives rise to the lesion this patient is experiencing?

A. Neural crest cells (Correct Answer)
B. Endoderm
C. Mesoderm
D. Ectoderm
E. Neuroectoderm

Explanation: ***Neural crest cells*** - The suspected lesion, given its description and the patient's family history of skin cancer, is likely a **melanoma**. - Melanoma originates from **melanocytes**, which are derived from **neural crest cells** during embryonic development. *Endoderm* - The endoderm gives rise to the **lining of the gastrointestinal and respiratory tracts**, as well as organs such as the liver and pancreas. - It is not involved in the formation of melanocytes or skin lesions like melanoma. *Mesoderm* - The mesoderm forms tissues such as **muscle, bone, cartilage, connective tissue**, and the circulatory system. - It does not directly give rise to melanocytes, which are the cells of origin for melanoma. *Ectoderm* - The ectoderm gives rise to the **epidermis, nervous system**, and sensory organs. - While melanocytes are found in the epidermis, they are specifically derived from the **neural crest (a sub-population of ectoderm)**, not the general ectoderm. *Neuroectoderm* - Neuroectoderm specifically refers to the ectoderm that develops into the **nervous system**. - While neural crest cells originate from the neuroectoderm, "neural crest cells" is a more precise answer for the origin of melanocytes.

Question 6: A 45-year-old woman presents to the clinic with a variety of complaints on different areas of her body, including telangiectasias on both the upper and lower extremities, bluish discoloration of the fingertips when exposed to cold, and burning midsternal chest pain. She is a tobacco smoker and works as a school teacher. After evaluation, an anti-centromere antibody test is ordered, and returns with an elevated titer. Which of the following symptoms are least likely to be seen in this patient's condition?

A. Gastroesophageal reflux
B. Spasm of blood vessels in response to cold or stress
C. Thickening and tightening of the skin on the fingers
D. Dysphagia
E. Erythematous periorbital rash (Correct Answer)

Explanation: ***Erythematous periorbital rash*** - An **erythematous periorbital rash** (**heliotrope rash**) is highly characteristic of **dermatomyositis**, not the patient's condition. - This symptom, along with **Gottron's papules** and **proximal muscle weakness**, would point away from scleroderma. *Gastroesophageal reflux* - **Gastroesophageal reflux** is common in **scleroderma**, particularly the limited cutaneous systemic sclerosis (CREST) variant. - Esophageal dysmotility and lower esophageal sphincter incompetence lead to reflux and **heartburn**. *Spasm of blood vessels in response to cold or stress* - This describes **Raynaud's phenomenon**, a hallmark feature of **limited cutaneous systemic sclerosis (CREST syndrome)**. - The patient's description of "bluish discoloration of the fingertips when exposed to cold" directly points to this symptom. *Thickening and tightening of the skin on the fingers* - **Sclerodactyly**, or thickening and tightening of the skin on the fingers, is a primary manifestation of **scleroderma**. - This is a key diagnostic criterion for systemic sclerosis, especially in the limited form. *Dysphagia* - **Dysphagia**, or difficulty swallowing, is very common in **scleroderma** due to **esophageal hypomotility** and fibrosis. - The sensation of food sticking or difficulty propelling food down the esophagus is a frequent complaint.

Question 7: A 49-year-old woman with a history of intravenous drug use comes to the physician because of a 6-month history of fatigue, joint pain, and episodic, painful discoloration in her fingers when exposed to cold weather. She takes no medications. She has smoked one pack of cigarettes daily for the past 22 years. She appears tired. Physical examination shows palpable, nonblanching purpura over the hands and feet. Neurological examination shows weakness and decreased sensation in all extremities. Serum studies show: Alanine aminotransferase 78 U/L Aspartate aminotransferase 90 U/L Urea nitrogen 18 mg/dL Creatinine 1.5 mg/dL Which of the following processes is the most likely explanation for this patient's current condition?

A. Fibroblast proliferation
B. Immune complex formation (Correct Answer)
C. Spirochete infection
D. Tobacco hypersensitivity
E. Plasma cell malignancy

Explanation: **Immune complex formation** * The patient's history of **intravenous drug use** and a constellation of symptoms including **fatigue**, **joint pain**, **Raynaud phenomena**, and **palpable purpura** are highly suggestive of **mixed cryoglobulinemia**. * **Mixed cryoglobulinemia** is characterized by the presence of **immune complexes** (immunoglobulins that precipitate in the cold) that can deposit in small and medium-sized vessels, leading to **vasculitis** and organ damage, often triggered by chronic infections like **Hepatitis C** (common in IV drug users). *Fibroblast proliferation* * While **fibroblast proliferation** is involved in fibrosis and scaring, it does not explain the widespread systemic symptoms such as **purpura**, **neuropathy**, and **renal involvement** seen here. * Conditions driven primarily by fibroblast proliferation, such as **scleroderma**, present with skin thickening and organ fibrosis but typically lack prominent vasculitic features like palpable purpura. *Spirochete infection* * **Spirochete infections** (e.g., syphilis, Lyme disease) can cause fatigue and joint pain, but they do not typically present with **palpable purpura**, **Raynaud phenomenon**, or the specific pattern of organ involvement (liver and kidney dysfunction) seen in this patient. * While syphilis can cause central nervous system issues, the **peripheral neuropathy** described here along with cutaneous vasculitis does not align with a typical spirochetal presentation. *Tobacco hypersensitivity* * **Tobacco hypersensitivity** is not a recognized medical condition explaining this array of symptoms. * Smoking is a risk factor for various vascular diseases (e.g., Buerger's disease), but it does not cause **immune-complex mediated vasculitis** with palpable purpura and neuropathy. *Plasma cell malignancy* * **Plasma cell malignancies** like **multiple myeloma** can cause fatigue, kidney problems, and neuropathy due to monoclonal immunoglobulin deposition or amyloidosis. * However, **palpable purpura** and **Raynaud phenomena** are very uncommon primary manifestations of plasma cell malignancies, making immune complex vasculitis a more fitting diagnosis for this patient's presentation.

Question 8: A 48-year-old male presents to his primary physician with the chief complaints of fever, abdominal pain, weight loss, muscle weakness, and numbness in his lower extremities. UA is normal. A biopsy of the sural nerve reveals transmural inflammation and fibrinoid necrosis of small and medium arteries. Chart review reveals a remote history of cigarette smoking as a teenager and Hepatitis B seropositivity. What is the most likely diagnosis?

A. Raynaud disease
B. Systemic lupus erythematosus
C. Microscopic polyangiitis
D. Thromboangiitis obliterans
E. Polyarteritis nodosa (Correct Answer)

Explanation: ***Polyarteritis nodosa*** - The constellation of **fever, abdominal pain, weight loss, muscle weakness, and numbness in the lower extremities** (suggesting **neuropathy**) along with **Hepatitis B seropositivity**, is highly indicative of **Polyarteritis nodosa (PAN)**. - The **sural nerve biopsy findings of transmural inflammation and fibrinoid necrosis of small and medium arteries** are pathognomonic for PAN, confirming a **necrotizing vasculitis** primarily affecting these vessel types. *Raynaud disease* - This condition involves **vasospasm of small arteries and arterioles**, typically in the fingers and toes, leading to characteristic color changes. - It does not present with systemic symptoms like **fever, weight loss, or abdominal pain**, nor does it cause **transmural inflammation or fibrinoid necrosis** of arteries. *Systemic lupus erythematosus* - SLE is a multisystem autoimmune disease that can cause a wide range of symptoms, but it is not typically characterized by **necrotizing vasculitis of small and medium arteries** with **fibrinoid necrosis** as seen in the biopsy. - While it can cause neuropathy, the specific biopsy findings and the strong association with **Hepatitis B** make PAN a more fitting diagnosis. *Microscopic polyangiitis* - **Microscopic polyangiitis (MPA)** is a **pauci-immune necrotizing vasculitis** that primarily affects **small vessels** (capillaries, venules, arterioles) and is often associated with **ANCA** (anti-neutrophil cytoplasmic antibodies). - While it can cause systemic symptoms and neuropathy, the biopsy finding of **transmural inflammation affecting medium arteries** and the strong link to **Hepatitis B** point away from MPA and towards PAN. *Thromboangiitis obliterans* - This is a **segmental, thrombosing vasculitis** primarily affecting **small and medium arteries and veins of the extremities**, almost exclusively seen in **smokers**. - While the patient has a remote history of smoking, the biopsy finding of **transmural inflammation and fibrinoid necrosis** is typical of PAN, not the thrombosing inflammation of Thromboangiitis obliterans.

Question 9: A 67-year-old man presents to the emergency department with increased fatigue. He states that he has been feeling very tired lately but today lost consciousness while walking up the stairs. He reports mild abdominal distension/discomfort, weight loss, a persistent cough, and multiple episodes of waking up drenched in sweat in the middle of the night. The patient does not see a primary care physician but admits to smoking 2 to 3 packs of cigarettes per day and drinking 1 to 3 alcoholic beverages per day. He recently traveled to Taiwan and Nicaragua. His temperature is 99.5°F (37.5°C), blood pressure is 177/98 mmHg, pulse is 100/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you note a fatigued appearing elderly man who is well-groomed. Cardiopulmonary exam reveals mild expiratory wheezes. Abdominal exam is notable for a non-pulsatile mass in the left upper quadrant. Laboratory values are ordered as seen below. Hemoglobin: 12 g/dL Hematocrit: 36% Leukocyte count: 105,500/mm^3 Platelet count: 197,000/mm^3 Serum: Na+: 139 mEq/L Cl-: 100 mEq/L K+: 4.3 mEq/L HCO3-: 25 mEq/L BUN: 20 mg/dL Glucose: 92 mg/dL Creatinine: 1.4 mg/dL Ca2+: 10.2 mg/dL Leukocyte alkaline phosphatase score: 25 (range 20 - 100) AST: 12 U/L ALT: 17 U/L Which of the following is the most likely diagnosis?

A. Tuberculosis
B. Leukemoid reaction
C. Acute myelogenous leukemia
D. Acute lymphoblastic leukemia
E. Chronic myeloid leukemia (Correct Answer)

Explanation: ***Chronic myeloid leukemia*** - The patient presents with **fatigue, weight loss, night sweats, and a persistent cough**, which are common symptoms of CML. The **extreme leukocytosis (105,500/mm^3)**, **non-pulsatile LUQ mass (splenomegaly)**, and a **low-normal leukocyte alkaline phosphatase (LAP) score of 25** are highly indicative of CML. - CML characteristically shows a **low LAP score (typically <20)**, which distinguishes it from a leukemoid reaction. This patient's LAP of 25, while technically within the normal range (20-100), is at the lower end and consistent with CML. - CML is a myeloproliferative disorder characterized by the **Philadelphia chromosome (BCR-ABL fusion gene)**, leading to uncontrolled proliferation of myeloid cells. *Tuberculosis* - While **fatigue, weight loss, night sweats, and cough** can be present in tuberculosis, the **dramatically elevated leukocyte count** and **splenomegaly** are not characteristic findings of TB. - Tuberculosis would typically show a more prominent respiratory symptomology (e.g., hemoptysis) and imaging findings consistent with lung involvement, and its diagnosis would be confirmed by microbiologic studies. *Leukemoid reaction* - A leukemoid reaction is a **reactive leukocytosis (>50,000/mm^3)** often triggered by severe infection or inflammation, but it would present with an **elevated leukocyte alkaline phosphatase (LAP) score (typically >100)**, which contradicts the patient's low-normal LAP score of 25. - Unlike CML, a leukemoid reaction does not typically cause **splenomegaly** to the extent that it forms a palpable mass. *Acute myelogenous leukemia* - AML typically presents with **malignant myeloid blasts** in the peripheral blood (often >20%) and bone marrow, and patients are usually more acutely ill with symptoms related to **pancytopenia** (e.g., severe anemia, thrombocytopenia with bleeding), which are not present in this case. - While AML can cause leukocytosis, it is characterized by a **predominance of immature blast cells** rather than the mature granulocytes seen in CML. *Acute lymphoblastic leukemia* - ALL is primarily a disease of **lymphoid progenitor cells** and is more common in children, though it can occur in adults. It is characterized by the presence of **lymphoblasts** in the blood and bone marrow. - While it can cause fatigue and weight loss, the **extremely high leukocyte count composed primarily of mature myeloid cells** and **prominent splenomegaly** are inconsistent with ALL.

Question 10: A 24-year-old man presents to the clinic with the complaint of a new rash. The lesions are not bothersome, but he is worried as he has never seen anything like this on his body. Upon further questioning the patient states has been generally healthy except for a one time "horrible" flu-like episode two months ago in June. He has since gotten better. On physical exam the following rash is observed (Figure 1). What is the cause of this patient's rash?

A. Molluscum contagiosum virus (Correct Answer)
B. Varicella zoster virus (VZV)
C. Human immunodeficiency virus (HIV)
D. Human papilloma virus (HPV)
E. Staphylococcus aureus cellulitis

Explanation: ***Molluscum contagiosum virus*** - The image displays characteristic **umbilicated papules**, which are pathognomonic for **molluscum contagiosum**, a viral skin infection. - The history of a "horrible" flu-like episode two months prior could suggest recent **immunocompromise** or an acute retroviral syndrome, making the patient more susceptible to or exacerbating molluscum contagiosum. *Varicella zoster virus (VZV)* - VZV typically causes **vesicles on an erythematous base** that evolve into **crusted lesions** in a dermatomal distribution (shingles) or widespread (chickenpox), which is not consistent with the described rash. - While VZV can reactivate due to immunocompromise, the morphology of the rash does not fit a typical VZV presentation like chickenpox or shingles. *Human immunodeficiency virus (HIV)* - While **HIV infection** can lead to various skin manifestations, including increased susceptibility to molluscum contagiosum, it is not the direct cause of the rash itself. - The flu-like episode could represent acute retroviral syndrome, but HIV itself does not cause this specific papular rash, rather it creates an environment for opportunistic infections or conditions like molluscum. *Human papilloma virus (HPV)* - HPV causes **warts** (verrucae) which are typically **rough, hyperkeratotic papules** or lesions with a cauliflower-like appearance, a different morphology than seen in the image. - While HPV infections are common, the characteristic smooth, umbilicated papules seen here are not consistent with typical HPV-induced lesions. *Staphylococcus aureus cellulitis* - **Cellulitis** is a **bacterial skin infection** characterized by localized areas of **redness, warmth, swelling, and pain**, often with poorly defined borders, which are absent in this presentation. - **Staphylococcus aureus** can cause various skin infections, but not the distinct umbilicated papules observed in the image; these lesions are viral, not bacterial.

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