Measles (Rubeola)

Causative Agent & Transmission

Pathogenesis

• SLAMF1 (Signaling Lymphocytic Activation Molecule Family Member 1) - expressed on activated lymphocytes, dendritic cells, and monocytes; serves as the initial receptor
• Nectin-4 - on the basal surface of epithelial cells; important for respiratory entry and replication

• Robbins, Cotran & Kumar Pathologic Basis of Disease

Clinical Features

Prodrome (days 1-4)

• High fever
• Malaise
• Conjunctivitis ("red eyes")
• Coryza (runny nose), sneezing
• Prominent cough

Koplik Spots (pathognomonic)

Koplik spots. - Andrews' Diseases of the Skin, p. 458

Exanthem (Rash)

• Starts at the anterior scalp line and behind the ears
• Spreads over the face first, then over 2-3 days extends downward to trunk and extremities (cephalocaudal spread - this is slower than rubella)
• Lesions begin as discrete erythematous papules that coalesce
• Most prominent and confluent in earlier-affected areas; more discrete on extremities
• Purpura may be present on the extremities
• After 6-7 days, the rash clears with simultaneous fever resolution

Differential Diagnosis

Pathology (Microscopy)

• Skin rash: dilated vessels, edema, mononuclear perivascular infiltrate
• Koplik spots: necrosis, neutrophilic exudate, neovascularization near Stensen ducts
• Lymphoid organs: marked follicular hyperplasia, large germinal centers, and Warthin-Finkeldey cells - pathognomonic multinucleate giant cells with eosinophilic nuclear and cytoplasmic inclusion bodies (also found in the lung and sputum)

Complications

Diagnosis

• Clinical (Koplik spots + prodrome + cephalocaudal rash)
• Serology (IgM antibodies)
• PCR for viral RNA in respiratory secretions or urine
• Warthin-Finkeldey giant cells on histology (lung, lymph nodes)

Treatment

Vaccination (MMR)

• Two doses of MMR (Measles-Mumps-Rubella) vaccine are required for full protection
• Herd immunity threshold: ~95% coverage needed to achieve measles elimination
• MMR is contraindicated in: pregnancy, severe immunocompromise (except non-severely immunocompromised HIV patients), and history of anaphylaxis to a prior dose
• Common adverse effects: fever (<15%), rash (5%), transient lymphadenopathy (20%)
• Persons born before 1957 are generally considered immune from natural infection
• Goldman-Cecil Medicine International Edition

Current Epidemiology (2025-2026)

• The U.S. experienced its worst measles year since 1992 in 2025, with 3 deaths - more than in any year since measles elimination was declared in 2000
• In 2026, cases are already outpacing 2025. As of mid-2026, South Carolina alone has recorded over 600 confirmed cases, constituting the largest measles outbreak in U.S. history since elimination
• 94% of confirmed 2026 cases are in unvaccinated individuals
• The U.S. is at serious risk of losing its measles elimination status (Canada lost its status in November 2025 after 12+ months of continuous transmission)
• The CDC reports that falling vaccination coverage, increasing global measles activity, and travel-related importations are driving this surge
• Nationally, ~90% of Americans have received MMR, but in some regions coverage is below 60%, creating pockets of vulnerability

Recent Evidence

• MMR vaccine effectiveness remains high in African children (Endalamaw et al., 2024, PMID 39574018)
• Secondary vaccine failure can lead to onward transmission during outbreaks (Tranter et al., 2024, PMID 39173667)
• Adverse events following measles vaccines in infants <12 months are characterized and generally mild (Vittrup et al., 2025, PMID 39799850)

Diastasis Recti vs. Ventral Hernia

The Key Anatomical Distinction

"This is not a true hernia as the midline fascia is intact, and as such incarceration and strangulation do not occur." - Schwartz's Principles of Surgery, 11th Ed.

"Patients often mistake diastasis recti for ventral hernia. Diastasis recti is a separation of the rectus abdominis muscles without a defect in the abdominal fascia... No fascial ring can be palpated." - Sleisenger & Fordtran's GI & Liver Disease

Diastasis Recti - In Detail

Epidemiology & Risk Factors

• Very common postpartum (up to 66% of women in the third trimester)
• Obesity
• Multiple pregnancies, older maternal age, cesarean sections
• Connective tissue disorders
• Congenital cases in newborns
• Males: less common but increasingly recognized (Axelsen et al., 2026 - PMID 41652086)

Clinical Features

• Fusiform midline bulge (long and wide, not focal)
• Bulge worsens with Valsalva or with rectus contraction (e.g., doing a sit-up)
• No palpable fascial ring edge
• May cause: back pain, abdominal wall weakness, difficulty engaging the core, cosmetic distress
• No bowel obstruction or acute abdomen

Diagnosis

• Often clinical (physical exam sufficient)
• Ultrasound: confirms diagnosis, measures inter-recti distance (IRD), rules out coexisting hernia
• CT scan: measures muscle separation precisely, useful when diagnosis is uncertain

Management

1. Conservative (first-line):
   • Weight loss
   • Physical therapy - targeted core exercises (postpartum exercise reduces risk of progression)
   • Note: standard sit-ups and crunches can worsen diastasis and should be avoided in early rehab
2. Surgical (selected cases):
   • Indications: disabling abdominal wall dysfunction, failure of conservative therapy, cosmesis
   • Open or laparoscopic plication of the rectus sheath (midline fascial tightening)
   • Mesh can be added but increases complication rates
   • High long-term recurrence risk
   • Also introduces a new risk of incisional hernia

Ventral Hernia - In Detail

Classification

• Bailey and Love's Short Practice of Surgery, 28th Ed.

Risk Factors

• Prior abdominal surgery (incisional hernia)
• Obesity, advanced age, diabetes
• Wound infection after laparotomy
• Glucocorticoid use, immunosuppression
• Smoking, collagen vascular disease
• Vertical midline incisions (higher risk than transverse)

Clinical Features

• Focal bulge with a palpable fascial ring/neck
• Reducible (contents go back into abdomen) or irreducible
• Complications: incarceration (contents trapped, bowel obstruction) and strangulation (vascular compromise - surgical emergency)

Diagnosis

• Clinical exam (palpable defect edges)
• CT scan (gold standard): defines defect size, contents, and anatomy for surgical planning
• Ultrasound: useful for small or occult defects

Management

• Watchful waiting: acceptable for small, asymptomatic hernias containing only fat (low strangulation risk)
• Elective repair: indicated for symptomatic hernias causing pain or obstructive symptoms
• Urgent repair: incarcerated hernia not reducible
• Emergency repair: strangulated hernia
• Mesh-based repair recommended for defects >2 cm and all incisional hernias
• Primary suture repair acceptable only for small primary hernias <2 cm
• Approaches: open, laparoscopic (lower wound complications), or robotic

Coexistence & Clinical Importance

• In a series of small umbilical/epigastric hernias, concomitant diastasis recti was found in 45% of patients
• Diastasis is a risk factor for hernia recurrence after suture repair - mesh should be strongly considered when diastasis is present alongside a small primary hernia
• Hernia repair alone without midline reinforcement in a patient with diastasis significantly increases the recurrence rate (31.2% in one series)
• Patients undergoing complex abdominal wall reconstruction should have their diastasis addressed at the same time

"Management of diastasis recti is a trending topic without consensus... Diastasis recti has been shown to be a risk factor for recurrence after suture repair of a primary VH." - Sabiston Textbook of Surgery

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