Abnormal chest skiagram in a normal individual a case report on orphan lung disease – Pulmonary alveolar microlithiasis

D Suresh Kumar; K Gokul

doi:10.4103/japt.japt_3_22

CASE REPORT

Year : 2022 | Volume : 5 | Issue : 1 | Page : 41-43

Abnormal chest skiagram in a normal individual a case report on orphan lung disease – Pulmonary alveolar microlithiasis

D Suresh Kumar, K Gokul
Department of Chest Medicine, Meenakshi Medical College, Kanchipuram, Tamil Nadu, India

Date of Submission	07-Mar-2022
Date of Decision	05-Apr-2022
Date of Acceptance	02-Jun-2022
Date of Web Publication	12-Aug-2022

Correspondence Address:
K Gokul
Room No: 5, Sai Apartments, Balagi Nagar, Enathur, Kanchipuram 631552, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/japt.japt_3_22

Abstract

Pulmonary alveolar microlithiasis (PAM) is a rare inherited disorder of sodium phosphate cotransporter which causes accumulation of microliths in alveoli. This is a case report of a 46-year-old female, came for surgical fitness for laparoscopic cholecystectomy with abnormal chest skiagram. Chest skiagram showed typical sand storm appearance. Since the patient had no respiratory complaints, high-resolution computed tomography chest was taken which showed diffuse micronodular calcifications suggestive of PAM.

Keywords: Calcification, chest skiagram, pulmonary alveolar microlithiasis

How to cite this article:
Kumar D S, Gokul K. Abnormal chest skiagram in a normal individual a case report on orphan lung disease – Pulmonary alveolar microlithiasis. J Assoc Pulmonologist Tamilnadu 2022;5:41-3

How to cite this URL:
Kumar D S, Gokul K. Abnormal chest skiagram in a normal individual a case report on orphan lung disease – Pulmonary alveolar microlithiasis. J Assoc Pulmonologist Tamilnadu [serial online] 2022 [cited 2022 Oct 3];5:41-3. Available from: http://www.japt.com/text.asp?2022/5/1/41/353743

Introduction

Pulmonary alveolar microlithiasis (PAM) is a rare inherited disorder of sodium phosphate co transporter (Npt2b) in type 2 alveolar epithelial cells which causes accumulation of calcified microliths in the alveoli.^[1],[2] Majority of reported cases of PAM in literature are from Asia and Europe. The incidence of PAM in India is 0.06 per million persons.^[1],[3] Type 2 alveolar cells normally synthesize surfactants and maintain fluid balance. Pulmonary surfactant is normally made of phospholipids where they are broken down by alveolar macrophages. These breakdown releases phosphates which are removed by the Npt2b which is situated in the distal type 2 alveolar cells.

Case Report

A 46-year-old male never smoker, alcoholic admitted to the surgical ward for elective laparoscopic cholecystectomy. The patient was referred from the surgical ward for pulmonary fitness. Chest skiagram showed bilateral widespread diffuse symmetrical micronodular opacities suggestive of sand storm appearance [Figure 1]. Currently, the patient has no respiratory complaints and no significant history of tuberculosis, and no significant occupational and other exposure history. Routine investigations were normal. High-resolution computed tomography (HRCT) chest was taken which showed diffuse hyperdense ground-glass opacifications with linear calcifications are seen [Figure 2]. Spirometry shows a mild restrictive ventilatory defect. Sputum examination was inconclusive.

Figure 1: Chest skiagram shows bilateral widespread diffuse symmetrical micronodular opacities predominantly involving basal regions, a typical sandstorm appearance

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Figure 2: (a) HRCT chest shows diffuse hyperdense ground-glass opacifications with linear calcifications. (b) HRCT chest shows typical black pleura sign. HRCT: High-resolution computed tomography

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Since chest imaging is suggestive of PAM, we planned for fiberoptic bronchoscopic-guided biopsy, but the patient was not willing and she told that she will come to our outpatient department in case of any respiratory issues in near future. After that, patient underwent surgery and she was discharged successfully without any postoperative complications.

Discussion

PAM is a chronic lung disorder of Npt2b of type 2 alveolar epithelial cells. Genetic studies have revealed an SLC34A2 gene defect in few populations and which is an autosomal recessive pattern. Patients usually remain asymptomatic for a long time. Patients usually present as an incidental finding in their third to fourth decades of life. Patients will have mild dyspnea in the late stage and pneumothorax in rare cases. If patients are asymptomatic, then they can be left undisturbed as effective treatment is not available.

Radiological manifestation in pulmonary alveolar microlithiasis

Castellana et al.^[4] classified PAM into four stages.

Stage 1: Precalcified stage
Stage 2: Typical sand storm appearance
Stage 3: Progressive opacification with obscuring cardiac and diaphragm borders – vanishing heart phenomenon
Stage 4: Intense calcification – typical white-out lung.

The patient may have emphysematous changes, lung cyst, and pulmonary fibrosis.

Apart from lung, extrapulmonary microliths deposition can also occur in male external genitalia which may lead to male infertility.^[1]

In a large review from ERS journal, diseases reported to be associated with PAM included rheumatoid arthritis, Sjögren syndrome, lymphocytic interstitial pneumonitis, psoriasis, antiphospholipid syndrome, and discoid lupus after varicella-zoster infection, diaphyseal aclasia, autosomal recessive Waardenburg-anophthalmia, milk-alkali syndrome, pericardial cyst, osteopetrosis, pectus excavatum, and non-Hodgkin lymphoma.^[1]

HRCT chest should always be performed since it can reveal typical characteristic patterns of PAM, reserving lung biopsy for atypical cases.^[5]

Fiberoptic bronchoscopic-bronchoalveolar lavage may reveal microliths and bronchoscopy-guided transbronchial biopsy usually reveals microliths within the alveolar lumen.

Since PAM is a genetically transmissible disease by autosomal recessive pattern, familial screening mainly for siblings should be done by chest skiagram.^[6]

Currently, there is no effective treatment available for PAM. Low-phosphate diet and bisphosphate binders like etidronate can be tried in few patients who are symptomatic. Lung transplantation is the last resort and can be considered in symptomatic patients with the severe ventilatory defect.^[1],[7]

Differential diagnosis of PAM includes miliary tuberculosis, pneumoconiosis, fungal infection, sarcoidosis, tropical pulmonary eosinophilia, and metastasis.^[3]

Complication of pulmonary alveolar microlithiasis

Respiratory failure
Infections like tuberculosis
Pulmonary hypertension
Cor pulmonale
Pneumothorax
Male infertility.

Conclusion

PAM is an orphan lung disease that can affect middle-aged women, with chronic and deteriorating evolutionary course. Clinicians should be aware of its existence and its characteristic radiological feature.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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4.	Edelman JD, Bavaria J, Kaiser LR, Litzky LA, Palevsky HI, Kotloff RM. Bilateral sequential lung transplantation for pulmonary alveolar microlithiasis. Chest 1997;112:1140-4.
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