15.5 Rhinitis, Conjunctivitis, Eosinophilic & Mast Cell Disorders

1. Allergic Rhinitis

IgE-mediated inflammation of the nasal mucosa: sneezing, clear rhinorrhea, nasal congestion and itching of the nose, eyes and palate, with pale boggy turbinates, allergic shiners and a transverse nasal crease.

Classification by pattern (intermittent versus persistent) and severity guides treatment.

Therapy in evidence order:

Do not use intranasal decongestants for more than a few days — rhinitis medicamentosa (rebound congestion) follows, and it is a common cause of refractory congestion that resolves only with withdrawal.

Non-allergic rhinitis — vasomotor rhinitis triggered by temperature change, odors and alcohol; gustatory rhinitis; and drug-induced rhinitis from ACE inhibitors, alpha-blockers, beta-blockers, NSAIDs and oral contraceptives — mimics allergic rhinitis but lacks itching and sneezing and is not IgE-mediated.

Unilateral symptoms are a red flag: unilateral obstruction, purulent or bloody discharge, or facial pain suggests a foreign body, tumor, polyp, or cerebrospinal fluid rhinorrhea (clear fluid positive for beta-2 transferrin).

2. Sinusitis

Most acute sinusitis is viral and resolves without antibiotics. The clinical features that support acute bacterial rhinosinusitis are:

1. Symptoms persisting 10 days or more without improvement
2. Severe symptoms — high fever with purulent discharge and facial pain — for at least 3 to 4 consecutive days
3. Double worsening — initial improvement followed by deterioration

Amoxicillin-clavulanate is first-line when antibiotics are indicated. Watchful waiting with symptomatic care is appropriate in many patients.

Complications requiring urgent imaging: periorbital or orbital swelling, visual change or ophthalmoplegia (orbital cellulitis or abscess), severe headache with altered mental status (intracranial extension), or Pott puffy tumor (frontal bone osteomyelitis).

Chronic rhinosinusitis lasting 12 weeks or more is subclassified by the presence of nasal polyps, and polypoid disease should prompt consideration of aspirin-exacerbated respiratory disease, cystic fibrosis (particularly in a younger adult), and eosinophilic granulomatosis with polyangiitis.

Invasive fungal sinusitis — in a diabetic patient with ketoacidosis or a neutropenic patient, facial pain with a black eschar on the palate or turbinates is mucormycosis and is a surgical emergency.

3. Conjunctivitis and Upper Airway Cough Syndrome

Allergic conjunctivitis produces bilateral itching, tearing, conjunctival injection and chemosis, typically with rhinitis, and is treated with topical antihistamine-mast cell stabilizers. Itching is the cardinal symptom — its absence should make you doubt an allergic cause.

Upper airway cough syndrome is an enumerated topic and the most common cause of chronic cough in a non-smoker with a normal chest radiograph. Postnasal drainage and throat clearing with cobblestoning of the posterior pharynx; diagnosis is confirmed by response to an empiric first-generation antihistamine-decongestant, whose anticholinergic properties are part of the mechanism — second-generation agents are less effective for this indication.

4. Atopic and Contact Dermatitis

Skin disorders is an enumerated subsection under Allergy and Immunology listing atopic dermatitis and contact dermatitis.

Patch testing, not skin prick testing, diagnoses allergic contact dermatitis — a distinction the exam uses, since prick testing detects IgE-mediated sensitization and contact dermatitis is T-cell mediated. Common contact allergens include nickel, fragrance, preservatives, rubber accelerators, topical antibiotics (neomycin, bacitracin) and poison ivy urushiol.

Atopic dermatitis management: emollients, topical corticosteroids matched to site, topical calcineurin inhibitors and JAK inhibitors for sensitive areas, and biologics for severe disease. Recognize eczema herpeticum — abrupt monomorphic punched-out vesicles and erosions with fever in a patient with atopic dermatitis — as a dermatologic emergency requiring systemic acyclovir.

5. Mastocytosis and Mast Cell Disorders

Enumerated under autoimmune systemic disorders (including IgG4-related disorders).

Systemic mastocytosis results from clonal mast cell proliferation, usually driven by a KIT D816V mutation.

Clinical clues:

• Recurrent flushing, pruritus, hypotension and unexplained anaphylaxis, particularly severe reactions to hymenoptera stings
• Urticaria pigmentosa — reddish-brown macules that urticate when stroked (Darier sign)
• Abdominal pain, diarrhea, peptic ulceration
• Unexplained osteoporosis in a young person
• Hepatosplenomegaly and cytopenias in aggressive forms

Diagnosis: elevated baseline serum tryptase (measured at least 24 hours after any acute event, since tryptase rises transiently in anaphylaxis), followed by bone marrow biopsy with KIT mutation testing and CD25 expression.

Triggers to avoid: hymenoptera stings, opioids, radiocontrast, NSAIDs, alcohol, temperature extremes, and physical stimuli. Every patient should carry an epinephrine autoinjector.

Hereditary alpha-tryptasemia is a common cause of a modestly elevated baseline tryptase from increased TPSAB1 gene copy number, and must be distinguished from clonal mast cell disease.

6. The Eosinophilic Organ Diseases

The blueprint groups several eosinophil-driven conditions in this subsection, and they are unified by tissue eosinophilia with variable peripheral eosinophilia.

Before attributing eosinophilia to an allergic cause, exclude parasitic infection and drug reaction. Strongyloides must be excluded before corticosteroids in anyone with relevant exposure, because immunosuppression precipitates fatal hyperinfection syndrome.

Marked persistent eosinophilia above 1,500 per microliter with organ damage defines hypereosinophilic syndrome and requires evaluation for a clonal myeloid disorder.

7. IgG4-Related Disease

Explicitly named in the blueprint subsection heading. A fibroinflammatory condition producing tumefactive lesions — mass-like swellings that mimic malignancy — across multiple organs, typically in middle-aged and older men.

Organ manifestations that should trigger the thought:

Characteristic features: an elevated serum IgG4 (which is neither sensitive nor specific — it is normal in a substantial minority and elevated in other conditions), frequent allergic history and peripheral eosinophilia, and biopsy showing a dense lymphoplasmacytic infiltrate with storiform fibrosis, obliterative phlebitis and abundant IgG4-positive plasma cells.

The clinical importance is twofold: it is repeatedly mistaken for malignancy, leading to unnecessary resection — most notably the Whipple procedure performed for what proves to be autoimmune pancreatitis — and it responds dramatically to corticosteroids, with rituximab used for relapsing disease.