eMedicine Specialties > Pediatrics: General Medicine > Allergy & Immunology

Mold Allergy: Differential Diagnoses & Workup

Author: Shih-Wen Huang, MD, Medical Director of Allergy Service, Professor, Department of Pediatrics, Division of Immunology and Infectious Diseases, University of Florida College of Medicine
Contributor Information and Disclosures

Updated: Jun 15, 2009

Differential Diagnoses

Other Problems to Be Considered

Allergic rhinitis and allergic conjunctivitis

• Viral infectious rhinitis
• Nasal congestion as a complication of pregnancy
• Oral contraceptives
• Hypothyroidism
• Rhinitis medicamentosa (rebound vasodilation due to drugs such as Neo-Synephrine, terbutaline, and reserpine)
• Tumors
• Wegener granulomatosis

In children, the presence of congenital choanal atresia or a foreign body should be considered. The presence of nasal polyps should be carefully excluded.

Differential diagnoses for allergic conjunctivitis include but are not limited to infectious conjunctivitis (viral and bacterial) and vernal conjunctivitis.

Allergic asthma

For patients with wheezing, after a carefully obtained history, the following conditions must be excluded:

• Medical conditions involving the lung that manifest with symptoms suggestive of asthma
• Syndromes characterized by abnormal breathing in which the lungs are structurally normal
• Cases of local airway obstruction that manifest with wheezing that is audible to the patient or can be heard on examination

For those with cough without wheezing, the following conditions must be excluded:

• Cardiac failure with acute pulmonary edema
• Cardiac failure secondary to myocardial infarction
• Pulmonary embolism
• Pneumonia
• Tracheobronchitis

For children with wheezing or cough, asthma needs to be differentiated from the following conditions:

• Infections - Bronchiolitis, pneumonia, croup, tuberculosis, bronchitis
• Anatomic or congenital conditions - Cystic fibrosis (CF), vascular ring, dysmotile cilia syndrome, immune deficiency, congestive heart failure, laryngotracheomalacia, tracheoesophageal fistula, gastroesophageal reflux
• Hypersensitivity vasculitis - Allergic bronchopulmonary aspergillosis (ABPA), hypersensitive pneumonia, periarteritis nodosa
• Other - Foreign-body aspiration, pulmonary thromboembolism, psychogenic cough, sarcoidosis, bronchopulmonary dysplasia

Allergic fungal sinusitis

Differential diagnoses include conditions that lead to chronic sinus diseases, including the following:

• Immune deficiency
• Ciliary dyskinesia
• Aspirin hypersensitivity with nasal polyp
• Anatomic defect with small ostium of sinus
• Poorly treated sinusitis

Poor response to prolonged antibiotic treatment should raise the suspicion for allergic fungal sinusitis (AFS), and a workup for the disease should be initiated.

Allergic bronchopulmonary aspergillosis and allergic bronchopulmonary mycosis

The following conditions and findings must be excluded for diagnosis:

• Asthma not associated with mold allergy
• Chest radiographic infiltrate (eg, atelectasis, mucoid impactions, middle-lobe syndrome)
• Bronchiectasis caused by other diseases
• Other forms of hypersensitivity pneumonitis

Extrinsic allergic alveolitis

Individuals who are exposed to mycotoxin in an atmosphere with molds may develop symptoms of respiratory illness now defined as organic dust toxic syndrome. The disease is due to toxicity, not hypersensitivity. Another condition that must be excluded is nitrogen oxide pneumonitis, which is reported in individuals working in silos.

Other diseases that should be excluded include the following:

• Cryptogenic fibrosing alveolitis
• Sarcoidosis
• Pneumoconiosis
• Tuberculosis
• Metastatic cancer of the lung

Any infection, inflammation, or drug reaction leading to a fibrotic process of the lung also should be considered as differential diagnosis.

Worth re-emphasis is that mold-exposed patients can present with various immunoglobulin E (IgE)-mediated and non-IgE-mediated symptoms. Mycotoxins, irritation by spores, or metabolites may be culprits in non-IgE–mediated presentations; environmental assays have not been perfected. Symptoms attributable to the toxic effects of molds and not attributable to IgE or other immune mechanisms need further evaluation regarding their pathogenesis. However, immune, rather than toxic, responses seemed to be the major causes of symptoms in most studies.

Workup

Laboratory Studies

The diagnosis of fungal sensitivity heavily depends on skin tests with fungal allergens. However, the variability and complexity of fungal extracts often hamper diagnosis. One of the breakthroughs of antigenic (Ag) preparation occurred when a recombinant form of a fungal allergen became available. Asturias et al compared a purified natural Aspergillus Ag (nAlt a) and recombinant Ag (rAlt a 1).¹⁰ They found a statistically significant correlation in specific immunoglobulin E (IgE) levels to both Ags by using skin test and immunoblotting/inhibition analysis. Therefore, the use of recombinant Ag may help in reducing the inconsistency of test results with the use of natural Ags.

• Allergic rhinitis and/or conjunctivitis
  • Immediate hypersensitivity skin testing: This test is the most useful method to detect IgE antibody against mold allergens. Testing can be performed by using the prick or intradermal method. The preferred site is the upper part of the back for the prick method or the arms for the intradermal method. Histamine and normal sodium chloride solution are most commonly used as positive and negative controls, respectively. Results are recorded 15 minutes after the test is performed. Wheal diameter more than 3 mm above the reaction of the negative control is considered a positive result. Mold allergen extracts used for the skin test depend on the prevalence of various molds in the region, as identified with annual atmospheric sampling. The most common molds are Alternaria, Aspergillus, Cephalosporium, Curvularia, Epicoccum, Fusarium, Helminthosporium, Hormodendrum, Mucor, Penicillium, Phoma, Pullularia, Rhizopus, and Stemphyllium species.
  • Radioallergosorbent testing (RAST): A positive result confirms allergen-specific IgE in the peripheral blood. The test is indicated in individuals who have clinically significant dermatographism or extensive skin disease, those who cannot discontinue antihistamines or other medications with antihistamine actions (eg, tricyclic antidepressants), or those who have a history of anaphylactic reaction (because direct application of the suspected allergen may precipitate recurrent anaphylaxis). RAST is not generally considered as sensitive as skin testing.
  • Nasal cytology: The presence of more than 10% of eosinophils in the cell population in the nasal secretion supports the diagnosis. Hansel staining is used to identify eosinophils. Eye swab results can be used to diagnose allergic conjunctivitis. If neutrophils are present in more than 90% of the cell population, bacterial infection should be considered.
  • Sinus images may depict sinusitis or adenoid hypertrophy.
• Allergic asthma
  • Skin test or RAST: These tests are helpful in determining the offending airborne allergens.
  • Pulmonary function testing: Simple spirometry to measure airway flow rates can help in identifying reversible or fixed airway obstruction. A reduced forced vital capacity in the absence of airflow obstruction is supportive evidence of restrictive lung disease. Spirometry can be performed during the initial workup or a follow-up visit in an outpatient clinic. The patient can use a peak flow meter to monitor his or her airflow at home. Airflow rates can be helpful in determining necessary adjustments for medications, depending on the patient's clinical course.
• Allergic fungal sinusitis (AFS)
  • Allergy skin test or RAST: These tests can help in identifying immediate hypersensitivity to suspected fungi.
  • Nasal cytology: This test is most critical for establishing the diagnosis. Mucus samples are obtained. If positive, they should contain clinically significant amounts of eosinophils, Charcot-Leyden crystals, and hyphae of fungi (A fumigatus or Bipolaris, Curvularia, Alternaria, Exserohilum, Helminthosporium, or Rhizomucor species).
  • Fungal culture: Fungal cultures may further support the identification of the offending fungi. A sensitivity test can help in choosing an antifungal agent should such treatment be indicated.
  • Total serum IgE: A clinically significant elevation can be corroborative evidence for the diagnosis of AFS.
  • Precipitin test: The presence of immunoglobulin G (IgG) in blood against the offending fungi can be corroborative evidence for the diagnosis of AFS.
• Allergic bronchopulmonary aspergillosis (ABPA) and allergic bronchopulmonary mycosis (ABPM)
  • Skin test or RAST: These tests are used to confirm immediate hypersensitivity to A fumigatus or other offending fungi.
  • Precipitin test: Precipitin test is used to confirm the presence of a high titer of IgG antibody against specific fungal Ags. Healthy individuals may have circulating IgG antifungal antibodies in the absence of any fungal-related disease.
  • Total serum IgE: This measurement is usually more than 400 IU/mL.
  • Sputum analysis: Sputum may appear brown, orange, or gray. Hyphae of Aspergillus species or other fungi can be observed, or they grow from culture.
  • Other: Persistent eosinophilia of more than 0.5 X 10⁹/L (>500/µL) may be present.
  • One report indicated the bronchial alveolar lavage (BAL) typically reveals bronchial lymphocytosis with increased CD8+ T cells in patients with hypersensitive pneumonitis.¹¹ Lymphocyte counts from 30% to more than 50% are common. BAL fluid with less than 30% lymphocytes should put the diagnosis of hypersensitivity pneumonitis in question.
• Extrinsic allergic alveolitis
  • Immediate hypersensitivity intradermal skin test: If results are positive, they may reveal both immediate (20 min) and late-phase (4-6 h) reactions.
  • Precipitin test: This test reveals positive IgG antibody against Ags of the offending fungi.
  • Assay for cell-mediated immunity: A delayed-type skin reaction against offending fungal Ags may be positive, with wheal formation after 24-48 hours after the intradermal application of fungal Ag. Positive results on lymphocyte transformation tests against the offending fungi indicate type IV hypersensitivity. The test is not practical for clinical use.
  • Laboratory-based inhalation challenge test with aerosolized solutions of soluble Ags of the suspected fungus: This test may be used to reproduce symptoms. It should be performed only in a pulmonary function testing center with personnel who have extensive expertise in this area.
  • Monitoring: Serial monitoring of temperature, changes in circulating neutrophil and lymphocyte blood counts, and lung vital capacity may help in monitoring disease activity.

Imaging Studies

• Allergic rhinitis and/or conjunctivitis: Sinus radiographs are not usually necessary unless they are used to look for superimposed sinusitis.
• Allergic asthma
  • Chest radiographs are used only to look for an ongoing infection, such as middle-lobe syndrome or pneumonia, or for chronic changes of the lung in chronic asthma. A barium swallow study may be used to exclude tracheoesophageal fistula or vascular ring in infants with chronic wheezing.
  • Sinus radiographs are used to exclude sinusitis in recalcitrant asthma unresponsive to conventional therapy. Look for air-fluid level, mucosal thickening, or opacity in the sinus cavity.
  • CT scanning of the paranasal sinuses may help in excluding sinusitis in asthma that is unresponsive to conventional therapy. CT scanning of the paranasal sinuses is useful if surgery is indicated for a sinus infection. A lateral view helps in identifying patients with adenoid hypertrophy.
• AFS
  • CT scanning of the paranasal sinuses may reveal a persistently opacified sinus cavity despite prolonged antibiotic therapy. AFS commonly causes unilateral sinus opacification due to obstruction of the sinus ostium with thick, inspissated mucus. CT scanning should reveal a persistently opacified sinus cavity that may be expansile. CT scanning may also reveal high attenuation in the opacified sinus due to high protein concentration. In a series of 6 children with a diagnosis of allergic Aspergillus sinusitis, all 6 had CT findings of diffuse expansile sinus disease, and 4 had evidence of bony erosion, which raised the suspicion for malignancy.
  • Corresponding lesions have a characteristic hypointense appearance on T1-weighted and T2-weighted images on sinus MRIs. Such lesions are nearly pathognomic for AFS, but they are not always present.
• Allergic bronchopulmonary aspergillosis and allergic bronchopulmonary mycosis
  • Diagnostic signs on chest radiograph include pulmonary infiltrate, mucus plugging and the finger-in-glove sign (ie, distal occlusion of bronchi packed with secretion), and bronchiectasis. Another reason for chest imaging is to look for late changes of lung tissues, such as fibrosis, blebs, bullae, and/or spontaneous pneumothorax. A dilated bronchus is seen as a ring shadow on en face. On a coronal view, the dilated bronchus may be seen as a parallel line shadow. Both are unique to ABPA and ABPM.
  • Conventional CT scanning provides an axial perspective and can demonstrate proximal and distal bronchiectasis.
  • Bronchography demonstrates bronchiectasis, but it is associated with complications and generally not necessary since CT scanning is available. Bronchography is not recommended for children because of the need for general anesthesia.
• Extrinsic allergic alveolitis
  • A widespread ground-glass appearance or an alveolar filling pattern, particularly in the lower and middle zones, can be seen on a chest radiograph when the disease is moderately severe. The lesions may resolve after exposure ceases. If exposure continues, a nodular pattern or honeycombing may develop. When the upper zone is affected, it manifests as irreversible fibrosis.
  • In subacute cases, CT scans reveal reticular or nodular infiltration in parenchyma. In chronic cases, a similar pattern of fibrosis can be seen throughout the lung fields. Expiratory images may reveal patchy areas of increased lucency, indicating airtrapping.

Other Tests

• Pulmonary function tests are recommended for all fungal-induced pulmonary diseases, including asthma, ABPA, ABPM, and extrinsic allergic alveolitis (EAA), as a means for longitudinal monitoring of the clinical course.
• BAL is not indicated in clinical practice. However, studies demonstrated that, in ABPA, BAL samples yields higher IgE levels against the fungal Ag than do peripheral blood samples. This finding suggests the local production of IgE against Aspergillus species. In EAA, BAL is no more helpful than the demonstration of serum precipitins.

Procedures

• Rhinoscopy
  • Specimens obtained from the sinus cavity can be diagnostic in AFS by showing abundant eosinophils, Charcot-Leyden crystals, and hyphae of fungi. Rhinoscopy is also useful for culture for fungi and to determine if a nasal polyp is present.
  • For patients with chronic allergic rhinitis that is recurrent or resistant to conventional therapy, the procedure is helpful for identifying adenoid hypertrophy, chronic adenoiditis, nasal polyps, or ethmoidal bullae. If rhinitis is complicated with sinusitis, it helps to determine the obstruction of ostium of sinus tract and/or to collect discharge for microbiologic study.
• Bronchoscopy: Bronchoscopy is indicated only for selected patients for tissue diagnosis. It is not considered a routine procedure for any of the lower respiratory tract disorders, such as ABPA, ABPM, and EAA.

Histologic Findings

• Allergic rhinitis and/or conjunctivitis
  • In acute cases, submucosal cellular infiltration is limited.
  • Edema and vasodilation are obvious, indicating an immediate phase reaction. In subacute or recurrent rhinitis, goblet cells are increased.
  • Eosinophil, neutrophil, and plasma-cell infiltration is significant in the submucosal area.
  • In chronic cases, epithelial cells are often severely damaged or disrupted, exposing the submucosal layer. More mononuclear cells are found in the submucosa. Increased deposition of collagens is present. Immunohistochemical studies reveal heavy deposition of eosinophil cationic protein in the submucosa.
• Allergic asthma
  • Hyperinflation and airway plugging with exudate and mucus, especially in the bronchioles, can be seen postmortem.
  • Eosinophil infiltration is present in submucosa, and creola bodies are present. Surface epithelium shows significant disruption or loss.
  • The reticular basement membrane is homogeneously thickened with hyaline deposition. Smooth muscle in the larger airways is hypertrophied.
  • Edematous tissue is always present.
  • Bronchial glands are also enlarged.
  • Cellular infiltration is prominent with mononuclear cells positive for CD3, CD4, CD25, and IL-2 receptor (IL-2R), as well as many degranulated (activated) eosinophils.
  • Mast cells are notably increased in tissues.
• AFS
  • The swollen mucosa is covered with thick sinus secretions that appear as allergic mucin and are loaded with degranulating eosinophils.
  • Charcot-Leyden crystals can be found.
  • Hyphae of the offending fungi should be visible.
  • Sinus mucosal tissue characteristically shows intense chronic inflammation with a large number of eosinophils.
  • In 6 children with allergic Aspergillus sinusitis, all had multiple sinuses densely packed with greenish black, inspissated mucin.
• ABPA and ABPM
  • The bronchi contain thick, tenacious mucus with fibrin, eosinophils, and Charcot-Leyden crystals.
  • Aspergillus (in ABPA) or other fungi hyphae may be identified with special stains. No invasion of the bronchial wall occurs despite a large number of hyphae.
  • The upper lobe bronchi may be dilated and partially collapsed, whereas smaller bronchi are occluded with mucus.
  • Bronchial wall inflammation with mononuclear cells and/or eosinophils often is observed.
  • Some changes from asthma are expected to be apparent.
• EAA
  • In patients with acute and subacute forms of EAA, lung biopsy specimens may reveal noncaseating granulomas with foreign-body giant cells, large numbers of lymphocytes, foamy macrophages, and bronchiolitis fibrosa obliterans associated with centrolobular pneumonia.
  • Vasculitis is rare.
  • In chronic disease, the lesions become nonspecific as the granulomas disappear and fibrosis supervenes.
  • Interstitial pneumonitis persists, and bronchiolitis fibrosa obliterans may lead to peripheral destruction of alveolar walls.
  • The overall picture is a variable mixture of scarring pneumonitis, honeycombing, and emphysema.

Staging

Staging of mold allergy diseases depends on the affected organs. Staging of each of the 6 diseases discussed in this article is as follows:

• Allergic rhinitis and/or conjunctivitis: Mold allergy–induced allergic rhinitis and/or conjunctivitis usually manifests with perennial or year-round allergic symptoms; in the seasonal form of allergic rhinitis, symptoms correspond with seasonal changes. No staging is apparent from a clinical standpoint. 
• Allergic asthma: According to Global Initiatives for Asthma: Global Strategy for Asthma Management and Prevention, asthma can be classified into 4 stages according to its severity.
  • Stage I - Mild intermittent (symptoms <1 time per wk, nighttime symptoms <2 times per mo)
  • Stage II - Mild persistent (daytime symptoms >2 times per wk, nighttime symptoms >2 times per mo)
  • Stage III - Moderate persistent (symptoms daily, nighttime symptoms >1 time per wk)
  • Stage IV - Severe persistent (symptoms continuous, nighttime symptoms frequent)
• AFS: Most diagnoses of AFS are made after patients have prolonged sinusitis. The acute stage is not clinically apparent.
• ABPA and ABPM
  • Stage I (acute): Diagnostic criteria are met (ie, asthma without infiltrate, peripheral eosinophilia >8%, histologic diagnosis of mucus impaction, sputum positive for Aspergillus species or other fungus, positive skin test and precipitin to fungus, elevated total serum IgE).
  • Stage II (remission): This occurs after therapy with prednisone and with the lack of any subsequent radiologic findings for 6 months. IgE levels decline and stabilize. This stage may be permanent, but exacerbation may occur.
  • Stage III (exacerbation): Radiologic findings include increased infiltrates, and the total serum IgE level at least doubles. Symptoms, including wheezing, fever with a temperature around 38.5°C, myalgia, and sputum production, may be increased.
  • Stage lV (prednisone-dependent asthma): This occurs when repeated efforts to taper steroids fail. Diagnosis is established in some patients at this stage. Levels of IgE specific to fungi are elevated, as are precipitin antibody values. New infiltrates may be apparent if the prednisone dose is low.
  • Stage V (fibrotic): This is end-stage fibrotic lung disease. Irreversible obstructive and restrictive pulmonary physiologic abnormalities occur. Anti-fungal antibody titers remain high. Patients develop honeycomb fibrosis, cyanosis, arterial hypoxemia, and respiratory failure. Death occurs with cor pulmonale. No patients regress from stage V to stage lV.
• EAA
  • Acute form: This form is easily recognized because symptoms are quickly distressing and incapacitating and have a high degree of specificity. Patients have repeated episodes of an influenza-like illness accompanied by coughing and undue breathlessness 3-9 hours after exposure to the offending fungi. The sensitizing period may vary from weeks to years. Affected patients may soon be able to identify the causative environment. The exposure level determines the severity of the disease.
  • Chronic form: A slowly increasing loss of exercise tolerance occurs because of shortness of breath. This is the result of diffuse pulmonary fibrosis, which has been progressing for years. Eventually, hypoxia and pulmonary hypertension may supervene, and the right heart fails.
  • Intermediate form: Depending on the level of fungal Ags exposed and the host responses, various intermediate forms of EAA can be recognized. Therefore, acute exacerbation may occur in those with a chronic form of the disease with only a limited degree of recovery following cessation of exposure. However, in some cases, fibrotic damage continues, regardless of the cessation of exposure.

• Search for CME/CE on This Topic »

• Indoor Aeroallergens (Allergy and Immunology)

• Asthma Causes
• Asthma Center
• Asthma Overview
• Asthma Symptoms
• Asthma Treatment
• Occupational Asthma Overview
• Understanding Asthma Medications
• Asthma FAQs