Sarcoidosis - Diagnosis

Diagnosis

Diagnosis of sarcoidosis is often a matter of exclusion. To exclude sarcoidosis in a case presenting with pulmonary symptoms might involve chest X-ray, CT scan of chest, PET scan, CT-guided biopsy, mediastinoscopy, open lung biopsy, bronchoscopy with biopsy, endobronchial ultrasound and endoscopic ultrasound with FNA of mediastinal lymph nodes(EBUS FNA). Tissue from biopsy of lymph nodes is subjected to both flow cytometry to rule out cancer and special stains (acid fast bacilli stain and Gömöri methenamine silver stain) to rule out microorganisms and fungi. Angiotensin-converting enzyme blood levels are used in diagnosis and monitoring of sarcoidosis.

Differential diagnosis includes metastatic disease, lymphoma, septic emboli, rheumatoid nodules, Wegener's granulomatosis, varicella infection, and atypical infections, such as Mycobacterium avium complex, cytomegalovirus, and cryptococci. Sarcoidosis is confused most commonly with neoplastic diseases, such as lymphoma, or with disorders characterized also by a mononuclear cell granulomatous inflammatory process, such as the mycobacterial and fungal disorders.

Because of the wide range of possible manifestations, the investigations to confirm diagnosis may involve many organs and methods, depending on initial presentation.

Very often, sarcoidosis presents as a restrictive disease of the lungs, causing a decrease in lung volume and decreased compliance (the ability to stretch); hence, chest X-ray and other methods are used to assess the severity or rule out pulmonary disease.

The disease typically limits the amount of air drawn into the lungs, but produces higher than normal expiratory flow ratios. The vital capacity (full breath in, to full breath out) is decreased, and most of this air can be blown out in the first second. This means the FEV₁/FVC ratio is increased from the normal of about 80%, to 90%. Obstructive lung changes, causing a decrease in the amount of air that can be exhaled, may occur when enlarged lymph nodes in the chest compress airways or when internal inflammation or nodules impede airflow.

Chest X-ray changes are divided into four stages:

• Stage 1: bihilar lymphadenopathy
• Stage 2: bihilar lymphadenopathy and reticulonodular infiltrates
• Stage 3: bilateral pulmonary infiltrates
• Stage 4: fibrocystic sarcoidosis typically with upward hilar retraction, cystic and bullous changes

Although patients with stage 1 X-rays tend to have the acute or subacute, reversible form of the disease, those with stages 2 and 3 often have the chronic, progressive disease; these patterns do not represent consecutive "stages" of sarcoidosis. Thus, except for epidemiologic purposes, this X-ray categorization is mostly of historic interest.

Investigations to assess involvement of other organs frequently involve electrocardiogram, ocular examination by an ophthalmologist, liver function tests, renal function tests, serum calcium, and 24-hour urine calcium.

In sarcoidosis presenting in the Caucasian population, hilar adenopathy and erythema nodosum are the most common initial symptoms. In this population, a biopsy of the gastrocnemius muscle is a useful tool in correctly diagnosing the patient. The presence of a noncaseating epithelioid granuloma in a gastrocnemius specimen is definitive evidence of sarcoidosis, as other tuberculoid and fungal diseases extremely rarely present histologically in this muscle.

In female patients, sarcoidosis is significantly associated with hypothyroidism, hyperthyroidism and other thyroid diseases, hence close surveillance of thyroid function is recommended.