*From the Department of Internal Medicine, UPMC McKeesport, McKeesport, PA.
Correspondence to: Toni Sičenica, MD, MSc, Department of Internal Medicine, UPMC McKeesport, 1500 5th Ave, McKeesport, PA 15132; e-mail: email@example.com
55-year-old woman presented with intermittent palpitations. She received
a diagnosis of paroxysmal atrial fibrillation and was treated
accordingly. Her history was significant for lung disease, diagnosed
with chest radiograph when she was in her teens. Her brother had also
received a diagnosis of lung disease when he was in his late teens. She
is an accountant who does not smoke. She was treated with several
inhalers (albuterol, salmeterol, and fluticasone) and supplemental
oxygen at night and as required during the day. She did not undergo
lung biopsy and has been assessed for a possible lung transplantation.
Physical examination revealed a well-looking white female subject
comfortable at rest while receiving 2 L of oxygen. She was afebrile and
talking in full sentences. Her BP was 116/76 mm Hg, and her pulse was
irregular at 115 beats/min. Her respiratory rate was 24 breaths/min,
with oxygen saturation of 95%. She had early digital clubbing, with no
peripheral cyanosis or cervical/axillary lymphadenopathy. Chest
expansion was symmetrical. She had several scars over the left chest
consistent with previous tube thoracostomies. The percussion note was
resonant, and auscultation revealed attenuated breath sounds with
bilateral fine end-inspiratory crackles most pronounced over the lung
Findings of initial WBC count, hemoglobin, platelet count, and
electrolytes were normal. ECG revealed an irregular rhythm with absent
P waves and a fast ventricular rate consistent with atrial
fibrillation. Chest radiograph revealed almost complete “whiteout”
of both lung fields, with diffuse modular opacities (Fig 1
Pulmonary function testing revealed decreased lung volumes (vital and
total lung capacity to 64% and 61% of predicted, respectively) and
decreased diffusing capacity (diffusing capacity/alveolar volume of
Pulmonary alveolar microlithiasis (PAM) is a rare disease first
described by Harbitz in 1918.1 It is so rare that by 1975,< 100 cases were described in the literature. It is a disease of
unknown cause, where calcium phosphate microliths are deposited within
the lung alveoli.
Theories of pathogenesis are based on acquired abnormalities of calcium
and phosphate metabolism.2Although the microliths are
usually confined to the lungs, there are reports of microliths
appearing in other tissues (eg, kidneys, prostate,
sympathetic chain, and gonads).3 They have even been found
in the organs of other species (eg, orangutans and
More than half the cases occur in families, suggesting a genetic
defect.5 However, since siblings are predominantly
affected, it appears that environmental factors may be important as
Microliths are formed in the alveolar walls and are released into the
alveolar space. They range from 0.01 to 3 mm in size; they are round,
oval, or irregular in shape and have a concentric laminated appearance.
Initially, the alveolar walls appear normal and, later on, thicken with
fibrosis. Bullae often develop in the apices.
The radiographic features can be pathognomic. The basic pattern is a
fine sand-like opacification throughout the lungs, described as a“
sandstorm.”6 The individual microliths are well
defined and usually < 1 mm in diameter. Due to greater depth of lung
tissue, the number of microliths increases in the lower lung fields.
Pneumothorax, pleural thickening, and pericardial calcifications can
The differential diagnosis includes hemosiderosis, histoplasmosis,
stannosis, metastatic carcinomatosis, pulmonary adenomatosis, miliary
tuberculosis, pneumoconioses, sarcoidosis, amyloidosis and metastatic
pulmonary calcification associated with chronic renal failure and
Most patients are asymptomatic on presentation. There is a striking
contrast between the paucity of signs and symptoms and the marked
radiographic features. The initial symptoms are dyspnea on exertion and
a nonproductive cough. Auscultation may reveal diminished breath sounds
and fine inspiratory crackles. Subsequently, they may develop
respiratory failure with cyanosis and signs of right ventricular
In addition to the chest radiograph, other methods can be used to
establish the diagnosis of PAM. Surprisingly, microliths in the sputum
and BAL are not diagnostic, because patients with COPD and tuberculosis
expectorate microliths as well.8 CT and the
99mTc diphosphonate scan have been used to
confirm diffuse calcifications in PAM. CT scan of the chest reveals a
diffuse infiltrative pattern, and the 99mTc
diphosphonate scan reveals increased uptake of the isotope throughout
Pulmonary function studies are initially normal. About 30% of patients
with PAM eventually develop abnormal pulmonary function studies. In
most patients, a mild restrictive defect evolves. The most common
findings are decreased vital and total lung capacity, normal residual
volume/total lung capacity ratio, and decreased diffusing
There is no specific treatment for PAM. Bronchopulmonary lavage and
corticosteroids have no effect. Treatment is supportive with
supplemental oxygen. Some patients may benefit from lung
Become a CHEST member and receive a FREE subscription as a benefit of membership.
Individuals can purchase this article on ScienceDirect.
Individuals can purchase a subscription to the journal.
Individuals can purchase a subscription to the journal or buy individual articles.
Learn more about membership or Purchase a Full Subscription.
Institutional access is now available through ScienceDirect and can be purchased at myelsevier.com.
Some tools below are only available to our subscribers or users with an online account.
Download citation file:
Web of Science® Times Cited: 1
Customize your page view by dragging & repositioning the boxes below.
Enter your username and email address. We'll send you a reminder to the email address on record.
Athens and Shibboleth are access management services that provide single sign-on to protected resources. They replace the multiple user names and passwords necessary to access subscription-based content with a single user name and password that can be entered once per session. It operates independently of a user's location or IP address. If your institution uses Athens or Shibboleth authentication, please contact your site administrator to receive your user name and password.