A 40-year-old man presented with shortness of breath and cough. Chest radiography showed extensive bilateral nodular opacities (sandstorm-like) predominantly in the middle and lower lobe (fig 1A) in the absence of metabolic abnormalities. Pulmonary function test revealed restrictive pattern of ventilation. High resolution computed tomography (CT) scan showed ground glass and increased parenchymal attenuation with coarsened, coalescing, nodular alveolar infiltrates associated with thickening and nodularity of peribronchovascular, interlobular and subpleural interstitium (fig 1B). The changes were more pronounced and dense in the subpleural centrilobular area. Patent bronchi and interspersed subpleural emphysematous changes (producing black pleural line) were present. This was further confirmed by histopathological examination of the lung biopsy specimen which showed normal respiratory epithelium with dilated alveolar spaces containing calcific bodies; some of them were concentric (fig 2).
Figure 1.
(A) Chest radiograph showing sandstorm appearance with predominant involvement of middle and lower lobe. (B) High resolution computed tomography scan of the chest showing “crazy paving” appearance.
Figure 2.
(A) Photomicrograph of transbronchial lung biopsy stained with periodic acid–Schiff (PAS) showing normal respiratory epithelium with dilated alveolar spaces containing many calcific bodies, some of which show concentric calcification. (B) Photomicrograph of the lung biopsy showing dark blackish brown, concentric calcific material in the background of light brown interstitial fibrovascular structures. Von Kossa silver stain ×400.
Pulmonary alveolar microlithiasis (PAM) is a rare disorder of uncertain aetiology, with both sporadic and familial occurrence. The familial cases are known to be transmitted in autosomal recessive fashion with 100% penetrance. The gene responsible has been identified as a homogenous mutation in SLC34A2, which encodes a type IIb sodium phosphate co-transporter.1 PAM has striking discordance between the extent of radiologic involvement and the severity of clinical presentation.2 No treatment is required for asymptomatic patients, but severe cases require lung transplantation.
LEARNING POINTS
Pulmonary alveolar microlithiasis (PAM) has typical chest radiograph (sandstorm- like) and CT (ground glass and increased parenchymal attenuation with coarsened coalescing alveolar nodular infiltrates) abnormalities.
Transbronchial lung biopsy is crucial in confirming the diagnosis.
Footnotes
Competing interests: none.
Patient consent: Patient/guardian consent was obtained for publication
REFERENCES
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