20.4 Integumentary Infections: Viral Exanthems (Measles, Mumps, Rubella, Varicella, Smallpox & Mpox, Fifth Disease), Herpesviruses, Fungal Skin Infections and Tick-Borne Diseases
Key Takeaways
Measles begins with cough, coryza, conjunctivitis and Koplik spots, then a rash that spreads from the face downward; vitamin A reduces complications and deaths.
Parvovirus B19 causes slapped-cheek fifth disease in children, aplastic crisis in chronic hemolytic anemia and hydrops fetalis in pregnancy.
Varicella lesions appear in crops at different stages, whereas smallpox lesions are all at the same stage and concentrated on the face and limbs.
Dermatophytes show branching septate hyphae on KOH, while Malassezia furfur shows "spaghetti and meatballs" hyphae and yeasts in tinea versicolor.
Scrub typhus from Orientia tsutsugamushi, spread by chigger mites, causes fever with a painless black eschar and responds to doxycycline.
Why this area matters
The TOS integumentary area names:
- the viral rashes: measles, mumps, rubella, chickenpox, smallpox and fifth disease;
- fungal skin infections;
- tick-borne diseases.
Measles remains a threat in the Philippines whenever immunization coverage falls; a large outbreak in 2019 caused many deaths among unvaccinated children. Superficial fungal infections are among the most common skin complaints in the hot, humid climate. Questions describe the order of fever and rash, a pathognomonic sign or a KOH finding, and ask for the organism, complication or prevention.
Comparing the viral exanthems
| Disease (virus) | Prodrome and rash | Key signs and complications | Prevention |
|---|---|---|---|
| Measles (rubeola; paramyxovirus) | 3 to 4 days of fever with cough, coryza and conjunctivitis; Koplik spots on the buccal mucosa; maculopapular rash from hairline and face downward, fading with brownish staining | Pneumonia (the main killer), diarrhea, otitis media, encephalitis, later SSPE; worse with malnutrition and vitamin A deficiency; give vitamin A | Measles-containing vaccine (in the Philippine NIP at 9 and 12 months) |
| Rubella (togavirus) | Mild fever, rash spreading from the face in 3 days | Postauricular and suboccipital nodes, arthralgia in women; congenital rubella: cataracts, PDA, sensorineural deafness, "blueberry muffin" rash | MMR or MR vaccine; screen women before pregnancy |
| Mumps (paramyxovirus) | Fever, then parotitis that lifts the earlobe | Orchitis after puberty, aseptic meningitis, pancreatitis, deafness | MMR |
| Varicella (VZV) | Mild prodrome; itchy macules, papules, vesicles ("dew drops on a rose petal") and crusts in crops at different stages, mainly on the trunk | Bacterial superinfection, pneumonia in adults and pregnancy, encephalitis and cerebellar ataxia, Reye syndrome with aspirin; contagious until all lesions crust | Varicella vaccine; VZIG for exposed high-risk people |
| Smallpox (variola, a poxvirus; eradicated in 1980) | High fever, then deep, firm pustules all at the same stage, concentrated on the face and limbs, including palms and soles | Scarring, blindness | Smallpox vaccine (vaccinia) |
| Mpox (monkeypox, an orthopoxvirus) | Fever and marked lymphadenopathy, then vesicles and pustules, often anogenital during the 2022 global outbreak | Spread by close and sexual contact; isolate until lesions heal | Vaccine for high-risk contacts |
| Erythema infectiosum (fifth disease; parvovirus B19) | "Slapped cheek" rash, then a lacy, reticular rash on the limbs | Arthritis in adults; aplastic crisis in sickle cell disease and spherocytosis; hydrops fetalis | None |
| Roseola infantum (HHV-6) | 3 to 5 days of high fever in an infant, then a rash as the fever breaks | Febrile seizures | None |
| Hand, foot and mouth disease (coxsackie A16, enterovirus 71) | Oral ulcers, vesicles on the hands and feet | EV71 can cause brainstem encephalitis | Hygiene |
Superficial bacterial infections
- Impetigo:
- nonbullous impetigo (S. aureus or group A streptococcus) gives honey-colored crusts;
- bullous impetigo is caused by exfoliative toxin from S. aureus;
- it can be followed by post-streptococcal glomerulonephritis, but not rheumatic fever.
- Scarlet fever (group A streptococcal pyrogenic exotoxins):
- a sandpaper-like rash, strawberry tongue and circumoral pallor;
- Pastia lines in skin folds.
- Staphylococcal scalded skin syndrome: a superficial split at the granular layer, with a positive Nikolsky sign and spared mucosa.
- Scabies (Sarcoptes scabiei, a mite):
- burrows and intense night itching in the finger webs, wrists and genitals;
- treat the patient and all household contacts at once with 5% permethrin.
Herpesviridae Family Overview
The family Herpesviridae comprises large, enveloped, double-stranded linear DNA viruses characterized by lifelong latency in human tissues:
- Herpes Simplex Virus 1 (HSV-1): Latent in the trigeminal ganglia; causes herpes labialis (cold sores), keratitis (dendritic corneal ulcers on fluorescein stain), and temporal lobe hemorrhagic encephalitis (characterized by RBCs in CSF, altered mental status, and temporal seizures). Tzanck smear demonstrates multinucleated giant cells with Cowdry A inclusions.
- Herpes Simplex Virus 2 (HSV-2): Latent in the sacral ganglia; causes painful genital vesicular ulcers and aseptic meningitis.
- Varicella-Zoster Virus (VZV): Latent in the dorsal root ganglia; causes chickenpox (asynchronous vesicular rash exhibiting the "dew drops on a rose petal" appearance) and shingles (herpes zoster; painful dermatomal vesicular eruption).
- Epstein-Barr Virus (EBV): Latent in memory B-cells; binds CD21; causes infectious mononucleosis (triad of fever, tonsillar exudative pharyngitis, and posterior cervical lymphadenopathy, accompanied by heterophile antibodies on Monospot test and atypical CD8+ cytotoxic T-lymphocytes [Downey cells] on peripheral smear). Associated with Burkitt lymphoma ( translocation involving c-myc) and nasopharyngeal carcinoma.
- Cytomegalovirus (CMV): Latent in mononuclear leukocytes; causes mononucleosis-like syndrome (heterophile antibody-negative), congenital hearing loss with periventricular intracranial calcifications, and severe opportunistic retinitis, colitis, and esophagitis (linear mucosal ulcers) in AIDS. Histopathology shows enlarged cells with prominent "owl's eye" basophilic intranuclear inclusion bodies.
- Human Herpesvirus 8 (HHV-8): Causes Kaposi sarcoma; infects vascular endothelial cells, presenting with dark purplish-violaceous plaques or nodules in immunocompromised patients; biopsy confirms spindle cells with slit-like vascular channels.
Herpes zoster (shingles):
- Course: reactivation of VZV in a dorsal root or cranial nerve ganglion gives a painful, unilateral, dermatomal vesicular eruption.
- Herpes zoster ophthalmicus: involvement of the tip of the nose (Hutchinson sign) warns of eye disease.
- Ramsay Hunt syndrome: geniculate ganglion involvement causes facial palsy with ear vesicles.
- Treatment: antivirals within 72 hours reduce acute pain.
- Prevention: recombinant zoster vaccine is given to older adults.
Medical Mycology: Diagnostic Discriminators
Fungi are eukaryotic organisms possessing cell walls rich in chitin and beta-glucan, with ergosterol as the primary cell membrane sterol. They are classified morphologically as yeasts (unicellular), molds (filamentous hyphae), or dimorphic fungi (growing as molds at environmental temperatures and yeasts at human body temperature: "mold in the cold, yeast in the heat").
| Category & Organism | Morphological & Diagnostic Discriminators | Key Clinical Features & Pathophysiology |
|---|---|---|
| Dermatophytes (Trichophyton, Microsporum, Epidermophyton) | Branching septate hyphae on 10% Potassium Hydroxide (KOH) preparation; Microsporum exhibits green fluorescence under Wood's lamp | Invade keratinized stratum corneum, hair, and nails; cause tinea capitis, tinea corporis ("ringworm"), tinea cruris, tinea pedis, and onychomycosis; treated with topical antifungals or oral terbinafine/itraconazole |
| Malassezia furfur (Pityriasis / Tinea versicolor) | Dimorphic lipophilic fungus; 10% KOH skin scrapings demonstrate characteristic "spaghetti and meatballs" appearance (short, blunt, non-branching hyphae and round budding yeast clusters) | Superficial infection degrading skin lipids into dicarboxylic acids (azelaic acid), which inhibit tyrosinase and melanin synthesis; causes hypo- or hyperpigmented macules on the trunk and neck with fine scaling; treated with topical selenium sulfide or ketoconazole |
| Sporothrix schenckii (Sporotrichosis) | Thermally dimorphic: Mold with branching hyphae and daisy-wheel conidiophores at 25°C; pleomorphic, cigar-shaped budding yeasts in tissue at 37°C | Acquired through traumatic subcutaneous inoculation from plant thorns (classic "rose gardener's disease"); produces a primary erythematous papule that ulcerates, followed by ascending lymphocutaneous nodules tracing lymphatic drainage; drug of choice is Itraconazole |
| Candida albicans | Forms budding yeasts and pseudohyphae; produces true germ tubes (hyphal outgrowths without constrictions at the junction) when incubated in human serum at 37°C for 3 hours; terminal chlamydospores on cornmeal agar | Normal commensal of skin, oral cavity, and GI tract; causes oral thrush, vulvovaginitis (curd-like "cottage cheese" discharge with normal vaginal pH < 4.5), intertrigo, esophageal candidiasis (AIDS-defining illness), and catheter-related candidemia |
| Cryptococcus neoformans | Monomorphic encapsulated yeast; narrow-based budding; surrounded by a thick, clear glucuronoxylomannan polysaccharide capsule that excludes particles; visualized on India ink stain as bright halos against a dark background; mucicarmine stain stains capsule bright carmine red; urease-positive | Acquired through inhalation of aerosolized pigeon droppings; predilects for the central nervous system in immunocompromised hosts, causing subacute cryptococcal meningitis with elevated opening CSF pressure; treated with liposomal amphotericin B plus flucytosine |
| Aspergillus fumigatus | Monomorphic mold; branching septate hyphae at acute 45-degree angles; conidiophores with radiating chains of conidiospores | Causes three major clinical syndromes: (1) Allergic Bronchopulmonary Aspergillosis (ABPA) in asthmatics and cystic fibrosis (eosinophilia, elevated IgE); (2) Aspergilloma (fungus ball) growing inside pre-existing tuberculous lung cavities (exhibits the "air-crescent sign" or Monod sign on chest CT, causes severe hemoptysis); (3) Invasive Aspergillosis in neutropenic patients (angioinvasive, produces pulmonary infarction); drug of choice is Voriconazole |
| Mucor & Rhizopus (Mucormycosis) | Monomorphic molds; broad, non-septate (coenocytic) ribbon-like hyphae that branch at wide 90-degree / right angles | Angioinvasive fungi thriving in acidic, high-glucose, high-iron environments; classically causes rhino-orbital-cerebral mucormycosis in patients with diabetic ketoacidosis (DKA) and profound neutropenia; fungal hyphae invade blood vessels, penetrate the cribriform plate into the orbit and brain, producing facial pain, cranial nerve palsies, and a black necrotic eschar on the nasal mucosa or hard palate; treatment requires emergent surgical debridement and intravenous Liposomal Amphotericin B |
| Pneumocystis jirovecii | Atypical opportunistic fungus; cell membrane contains cholesterol rather than ergosterol (rendering it intrinsically resistant to azoles and amphotericin); cell wall contains beta-glucan | Visualized on Gomori methenamine silver (GMS) stain as round, cup-shaped or "crushed ping-pong ball" cysts within alveolar foamy exudates; cannot be cultured on artificial media; causes severe diffuse interstitial pneumonia in AIDS (CD4 < 200/uL); drug of choice for treatment and prophylaxis is Trimethoprim-Sulfamethoxazole (TMP-SMX) |
Common Filipino terms for superficial fungal infections:
- an-an: tinea versicolor;
- buni: tinea corporis or ringworm;
- alipunga: tinea pedis or athlete's foot.
Topical azoles or terbinafine treat most localized dermatophyte infections. Tinea capitis and onychomycosis need oral therapy, because topical drugs do not reach the hair follicle or nail.
Tick-borne, mite-borne and flea-borne diseases
| Disease (organism) | Vector | Features | Treatment |
|---|---|---|---|
| Scrub typhus (Orientia tsutsugamushi) | Chigger mites (larval trombiculid mites) in grassy and scrub areas | Fever, headache, lymphadenopathy, a painless black eschar at the bite site, maculopapular rash; pneumonitis and meningoencephalitis; reported in the Philippines | Doxycycline (azithromycin in pregnancy) |
| Murine typhus (Rickettsia typhi) | Rat fleas | Fever, headache, rash on the trunk spreading outward | Doxycycline |
| Rocky Mountain spotted fever (R. rickettsii) | Ticks (Americas) | Rash that starts on the wrists and ankles, then spreads to the trunk and palms and soles; vasculitis | Doxycycline, even in young children |
| Lyme disease (Borrelia burgdorferi) | Ixodes ticks (temperate regions) | Erythema migrans (expanding "bull's-eye" lesion), then facial palsy, heart block and arthritis | Doxycycline or amoxicillin |
| Ehrlichiosis and anaplasmosis | Ticks | Fever with leukopenia, thrombocytopenia and raised liver enzymes; morulae in white cells | Doxycycline |
Rickettsiae are obligate intracellular bacteria that infect vascular endothelium, causing vasculitis with rash, edema and organ dysfunction. The Weil-Felix test is outdated; diagnosis now uses specific serology or PCR. Doxycycline is the drug of choice for all rickettsial diseases at every age, because the benefit of a short course outweighs the small risk of tooth staining.
An unvaccinated 2-year-old from a crowded barangay has had 4 days of fever, cough, runny nose and red eyes, and now has a red maculopapular rash that began behind the ears and on the face and is spreading down the body. Small white spots on a red base are seen on the buccal mucosa. Besides supportive care, which treatment reduces complications and deaths?
Intravenous immunoglobulin within 72 hours of rash onset
Oral amoxicillin as routine prophylaxis for pneumonia
Oral acyclovir for 7 days
Vitamin A given orally on 2 consecutive days
A 9-year-old boy with hereditary spherocytosis has had fever and a red "slapped cheek" rash in his class. He now has severe pallor and fatigue. His hemoglobin has fallen from 10 to 5 g/dL, and the reticulocyte count is nearly zero. Which virus is responsible, and what is the mechanism?
Epstein-Barr virus, which causes autoimmune hemolysis through cold agglutinins
Parvovirus B19, which infects and kills erythroid progenitor cells through the P antigen
Rubella virus, which causes immune thrombocytopenia and bleeding
Human herpesvirus 6, which suppresses the bone marrow after roseola
A 28-year-old soldier returns from jungle training in the mountains with fever, severe headache, myalgia and a maculopapular rash on the trunk. Examination shows tender regional lymph nodes and a painless black crust surrounded by redness in the groin. Which drug should be started?
Chloroquine
Doxycycline
Ceftriaxone
Oseltamivir
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