Pulmonary interstitial glycogenosis in identical twins

Neonatal interstitial lung disease in a girl with Jacobsen syndrome: a case report

BACKGROUND

We report a case of the neonatal interstitial lung disease pulmonary interstitial glycogenosis in a girl with Jacobsen syndrome. While Jacobsen syndrome is caused by a deletion on the long arm of chromosome 11 and is genetically confirmed, pulmonary interstitial glycogenosis is of unknown etiology and is diagnosed by lung biopsy. Pulmonary interstitial glycogenosis has not previously been described in association with Jacobsen syndrome.

CASE PRESENTATION

A term newborn small for gestational age Caucasian girl presented with respiratory distress, pulmonary hypertension, congenital heart defects, immunodeficiency, and thrombocytopenia. She was diagnosed with Jacobsen syndrome, but also had pulmonary interstitial glycogenosis, which contributed to significant morbidity. There was striking clinical improvement after steroid treatment of the pulmonary interstitial glycogenosis.

CONCLUSIONS

Interstitial lung disease should be considered as a differential diagnosis when respiratory distress and hypoxemia in the perinatal period worsens or persists despite standard treatment. Importantly, pulmonary interstitial glycogenosis may be treatable with corticosteroids. Whether there is a genetic link between pulmonary interstitial glycogenosis and Jacobsen syndrome is still unknown.

Pediatric Interstitial (Diffuse) Lung Disease

Interstitial (diffuse) lung diseases in infants and children comprise a rare heterogeneous group of parenchymal lung disorders, with clinical syndromes characterized by dyspnea, tachypnea, crackles, and hypoxemia. They arise from a wide spectrum of developmental, genetic, inflammatory, infectious, and reactive disorders. In the past, there has been a paucity of information and limited understanding regarding their pathogenesis, natural history, imaging findings, and histopathologic features, which often resulted in enormous diagnostic challenges and confusion. In recent years, there has been a substantial improvement in the understanding of interstitial lung disease in pediatric patients due to the development of a structured classification system based on the etiology of the lung disease, established pathologic criteria for consistent diagnosis, and the improvement of thoracoscopic techniques for lung biopsy. Imaging plays an important role in evaluating interstitial lung diseases in infants and children by confirming and characterizing the disorder, generating differential diagnoses, and providing localization for lung biopsy for pathological diagnosis. In this chapter, the authors present the epidemiology, challenges, and uncertainties of diagnosis and amplify a recently developed classification system for interstitial lung disease in infants and children with clinical, imaging, and pathological correlation.

Isolated pulmonary interstitial glycogenosis associated with alveolar growth abnormalities: A long-term follow-up study

INTRODUCTION

Pulmonary interstitial glycogenosis (PIG) is a rare infant interstitial lung disease characterized by an increase in the number of interstitial mesenchymal cells, presenting as enhanced cytoplasmic glycogen, and is considered to represent the expression of an underlying lung development disorder.

METHODS

This study describes the clinical, radiological, and functional characteristics and long-term outcomes (median 12 years) of nine infants diagnosed with isolated PIG associated with alveolar simplification in the absence of other diseases.

RESULTS

All patients presented with tachypnea. Additionally, seven patients had breathing difficulties and hypoxemia. Abnormalities in chest-computerized tomography (CT) with a pattern of ground-glass opacity, septal thickening, and air trapping were observed in all individuals, with images suggesting abnormal alveolar growth (parenchymal bands and architectural distortion). All lung biopsies showed alveolar simplification associated with an increased number of interstitial cells, which appeared as accumulated cytoplasmic glycogen. In the follow-up, all patients were asymptomatic. The respiratory function test was normal in only two patients. Five children showed an obstructive pattern, and two children showed a restrictive pattern. Chest-CT, performed after an average of 6.5 years since the initial investigation, revealed a partial improvement of the ground-glass opacity pattern; however, relevant alterations persisted.

CONCLUSION

Although the patients with PIG in the absence of other associated pathologies had a good clinical outcome, significant radiographic alterations and sequelae in lung function were still observed after a median follow-up of 12 years, suggesting that PIG is a marker of some other persistent abnormalities in lung growth, which have effects beyond the symptomatic period.

Rare neonatal interstitial lung disease masquerading as pulmonary hemosiderosis

A preterm 32-week neonate presented on the 14th day of life with respiratory distress and cyanosis. The respiratory distress worsened progressively, which was managed with continuous positive airway pressure support. The neonate had blood-tinged oral secretions on the 39th day of life, for which bronchoscopy was performed, whose findings were suggestive of pulmonary hemosiderosis. Lung biopsy confirmed the diagnosis of pulmonary interstitial glycogenosis with pulmonary arterial hypertension. The neonate was treated successfully with systemic corticosteroids and discharged home at 3 months of age.

Early onset children's interstitial lung diseases: Discrete entities or manifestations of pulmonary dysmaturity?

Interstitial lung diseases in children (chILD) are rare and diverse. The current classifications include a group of early onset chILD specific to infancy, namely neuro-endocrine cell hyperplasia of infancy (NEHI), pulmonary interstitial glycogenosis (PIG) and the alveolar capillary-congenital acinar dysplasia (ACD-CAD) spectrum, as well as alveolar growth disorders. NEHI and PIG cells are seen in the normal developing foetal lung. We hypothesise that these conditions are in fact overlapping manifestations of pulmonary dysmaturity, respectively of airway, mesenchymal and vascular elements, rather than discrete clinical conditions in their own right. Clinically, these present as respiratory distress in early life. Mild cases rightly never undergo lung biopsy, and for these the clinical description 'persistent tachypnoea of infancy' has been proposed. In terms of pathology, we reviewed current literature, which showed that NEHI cells decline with age, and are not specific to NEHI, which we confirmed by unpublished re-analysis of a second dataset. Furthermore, specific genetic disorders which affect pulmonary maturation lead to a histological picture indistinguishable from NEHI. PIG and ACD-CAD are also associated with pulmonary growth disorders, and manifestations of PIG and NEHI may be present in the same child. We conclude that, contrary to current classifications, NEHI, PIG, and ACD-CAD should be considered as overlapping manifestations of pulmonary dysmaturation, frequently associated with disorders of alveolar growth, rather than as separate conditions. Identification of one of these patterns should be the start, not the end of the diagnostic journey, and underlying in particular genetic causes should be sought.

Pulmonary interstitial glycogenosis: Diagnostic evaluation and clinical course

OBJECTIVES

We sought to describe the phenotype for patients with P.I.G. including presentation, evaluation, cardiac co-morbidities, high resolution computed tomography findings, and outcomes.

METHODS

With institutional review board approval, we performed a retrospective review of patients with biopsy-proven P.I.G. Biopsies, high resolution chest computed tomography, and cardiac evaluations were reviewed and characterized by experts in each field.

RESULTS

Sixty-two percent of the patients were male. The median gestational age was 37 weeks (range 27-40). The median age at biopsy was 1.6 months (range 0.3-6 months). Structural heart disease was present in 63% of patients. Pulmonary hypertension (diagnosed by echocardiogram and/or cardiac catheterization) was noted in 38% of patients. Alveolar simplification was present in 79% of patients. Fifty percent of available biopsies revealed patchy disease. An increase in age at biopsy was associated with patchy (vs diffuse) disease. Ninety-two percent of patients were treated with systemic corticosteroids. Median age at last follow-up was 1234 days with a range of 37 days to 15 years. At the time of last follow-up, 12 patients were off all support, eight were on supplemental oxygen, two were mechanically ventilated, one underwent lung transplantation, and one died. CT findings commonly included ground glass opacities (86%) and cystic change (50%).

CONCLUSIONS

The P.I.G. phenotype has not been comprehensively described, and poor recognition and misconceptions about P.I.G. persist. P.I.G. is a disease that presents in early infancy, requires significant medical intervention, and frequently is seen in association with alveolar simplification and/or cardiovascular disease. CT findings include ground glass opacities and cysts. Patients should be monitored for pulmonary hypertension. Without life-threatening comorbidities, many patients do well over time, although respiratory symptoms may persist into adolescence.

Persistent Pulmonary Hypertension Without Underlying Cardiac Disease as a Presentation of Pulmonary Interstitial Glycogenosis

INTRODUCTION

Pulmonary interstitial glycogenosis (PIG) is an idiopathic lung condition that remains clinically underrecognized despite a growing body of literature.

CASE REPORT

We present a case of PIG with pulmonary hypertension without underlying cardiac disease. This patient presented with respiratory distress and spontaneous pneumothorax at 6 months of age. Laboratory and imaging investigations demonstrated nonspecific features, but refractory pulmonary hypertension was confirmed on cardiac catheterization. Lung tissue histopathology showed glycogen positive staining of the interstitial cells, consistent with PIG.

CONCLUSION

This unique case demonstrates that pulmonary hypertension can be seen in the setting of PIG without associated cardiac anomalies, and persists despite treatment in an otherwise self-limited condition.

Pulmonary interstitial glycogenosis in a patient with trisomy 21

Pulmonary interstitial glycogenosis is an interstitial lung disease of childhood that has been increasingly reported over the past decade. Here, we present a case of pulmonary interstitial glycogenosis associated with trisomy 21, pulmonary arterial hypertension, and congenital heart disease in a 34 week premature infant.

Irreversible Respiratory Failure in a Full-Term Infant with Features of Pulmonary Interstitial Glycogenosis as Well as Bronchopulmonary Dysplasia

Pulmonary interstitial glycogenosis (PIG) is a rare interstitial lung disease in the newborns. We report on the clinical presentation and pathological findings of a full-term male infant with pulmonary hypertension requiring extracorporeal membrane oxygenation (ECMO). An open lung biopsy demonstrated interstitial changes resembling pulmonary interstitial glycogenosis as well as bronchopulmonary dysplasia (BPD), without convincing evidence of maturational arrest, infection, alveolar proteinosis, or alveolar capillary dysplasia. The boy was treated with glucocorticoids and, after a few days, was weaned from ECMO. A few hours later, the patient died due to acute severe pulmonary hypertension with acute right ventricular failure. The etiology and underlying pathogenic mechanisms of PIG are unknown. The clinical outcomes are quite varied. Deaths have been reported when PIG exists with abnormal lung development and pulmonary vascular growth and congenital heart disease. No mortality has been reported in PIG together with BPD in full-term infants. In this article, we reported on a full-term infant with interstitial changes resembling PIG and BPD who expired despite no convincing evidence of an anatomical maturational arrest or congenital heart disease.

Pulmonary interstitial glycogenosis in a patient ultimately diagnosed with Noonan syndrome

We describe an infant prenatally diagnosed with hydrops fetalis ultimately found to have Noonan syndrome (NS). Prior to genetic confirmation of diagnosis, lung biopsy was performed which revealed widespread pulmonary interstitial glycogenosis (PIG), abnormal alveolarization, and mild inflammation. Although genetic alterations have been identified in NS, the mutations are heterogeneous and the diagnosis remains one of clinical suspicion. The combination of PIG and NS has not yet been documented in the literature. While the underlying pathophysiologic mechanism of PIG is unclear, we suggest that the mitogen-activated protein kinase signal transduction pathway members (PTPN11, KRAS, SOS1, RAF1, SHOC2, NRAS) involved in cellular growth factor signaling, which are affected in NS, can provide clues. In addition, this case demonstrates that empiric corticosteroids can be considered in complicated cases since biopsy did reveal an inflammatory component, not typically noted in PIG.

An infant with pulmonary interstitial glycogenosis: clinical improvement is associated with improvement in the pulmonary diffusion capacity

Pulmonary interstitial glycogenosis (PIG) is an idiopathic interstitial lung disease of infants. The underlying pulmonary pathophysiology of PIG has not been well characterized. Herein we report a term-gestation infant who presented with persistent tachypnea and hypoxia. A chest CT scan demonstrated a diffuse ground glass appearance and lung biopsy demonstrated increased alveolar septae cellularity with glycogen-containing cells, consistent with a diagnosis of PIG. At 3 months of age, pulmonary function testing included: pre- and post-bronchodilator forced expiratory flows using the raised-volume technique and the ratio of pulmonary diffusing capacity for carbon monoxide to alveolar volume (DLCO /VA ). He was prescribed 5 days of oral prednisolone (2mg/kg/day) and pulmonary function testing (PFT) was repeated at 5, 13, and 20 months of age. Initial PFTs demonstrated reduced forced vital capacity (FVC: Z-score = -2.36) and an increased ratio of forced expiratory volume in 0.5 sec to FVC (FEV0.5/FVC: Z-score = 1.15) with no significant change following an inhaled bronchodilator. There was also a marked reduction in DLCO /VA (Z-score = -4.74) compared to age-matched controls. Follow-up demonstrated progressive clinical improvement as well as an increase in Z-FVC and normalization of DLCO /VA . Our in vivo physiological findings are consistent with previous reports that symptom resolution correlated with histological thinning of the alveolar septae upon repeat lung biopsy. The restrictive lung disease we observed is consistent with expected reduced compliance of an alveolar interstitial lung process like PIG, whereas the absence of a reduction in FEV0.5/FVC confirms the absence of obstructive airway disease.

Diffuse Lung Disease

Diffuse lung disease (DLD) comprises a diverse group of disorders characterized by widespread pulmonary parenchymal pathology and impaired gas exchange. While many of these disorders are categorized under the rubric of interstitial lung disease (ILD), some of these disorders involve the airspaces or peripheral airways in addition to, or rather than, the interstitium. Some of these disorders are present primarily in infancy or early childhood, while others that are prevalent in adulthood rarely occur in childhood. This chapter will review the classification of pediatric DLD and the characteristic imaging findings of specific disorders to facilitate accurate diagnosis and guide appropriate treatment of children with these disorders.

Pulmonary interstitial glycogenosis associated with pulmonary hypertension and hypertrophic cardiomyopathy

A neonate with pulmonary interstitial glycogenosis, pulmonary hypertension, and hypertrophic cardiomyopathy is described. The fatal outcome for this patient contrasts with the reported favorable prognosis associated with isolated pulmonary interstitial glycogenosis. To the authors' knowledge, the association of pulmonary interstitial glycogenosis and hypertrophic cardiomyopathy has not been reported previously. The authors have broadened the phenotype of pulmonary interstitial glycogenosis and demonstrate the diagnostic value of lung biopsy in cases of unexplained neonatal pulmonary hypertension.

New coding in the International Classification of Diseases, Ninth Revision, for children's interstitial lung disease

The term "children's interstitial lung disease" (chILD) refers to a heterogeneous group of rare and diffuse lung diseases associated with significant morbidity and mortality. These disorders include neuroendocrine cell hyperplasia of infancy, pulmonary interstitial glycogenosis, surfactant dysfunction mutations, and alveolar capillary dysplasia with misalignment of pulmonary veins. Diagnosis can be challenging, which may lead to a delay in recognition and treatment of these disorders. Recently, International Classifications of Diseases, Ninth Revision codes have been added for several of the chILD disorders. The purpose of this article is to give an overview of the chILD disorders and appropriate diagnostic coding.

Interstitial Lung Disease in Infants and Children: New Classification System with Emphasis on Clinical, Imaging, and Pathological Correlation

Interstitial lung diseases in infants and children comprise a rare heterogeneous group of parenchymal lung disorders, with clinical syndromes characterized by dyspnea, tachypnea, crackles, and hypoxemia. They arise from a wide spectrum of developmental, genetic, inflammatory, infectious, and reactive disorders. In the past, there has been a paucity of information and limited understanding regarding their pathogenesis, natural history, imaging findings, and histopathologic features, which often resulted in enormous diagnostic challenges and confusion. In recent years, there has been a substantial improvement in the understanding of interstitial lung disease in the pediatric patient, due to the development of a structured classification system based on etiology of the lung disease, established pathologic criteria for consistent diagnosis, and improvement of thoracoscopic techniques for lung biopsy. Imaging plays an important role in evaluating interstitial lung diseases in infants and children by confirming and characterizing the disorder, generating differential diagnoses, and providing localization for lung biopsy for pathological diagnosis. In this chapter, the authors present epidemiology, challenges and uncertainties of diagnosis, and amplify a recently developed classification system for interstitial lung disease in infants and children with clinical, imaging, and pathological correlation.

Pulmonary maturational arrest and death in a patient with pulmonary interstitial glycogenosis

We present the clinical presentation and pathological findings from a term infant with atypical neonatal lung disease. A full term Caucasian male presented at birth with signs of respiratory distress. The respiratory condition continued to deteriorate despite maximum intervention and the patient was placed on ECMO for further cardiorespiratory assistance. An open lung biopsy demonstrated findings consistent with severe lung growth abnormality with non-uniform pulmonary interstitial glycogenosis. The patient consequently developed a pulmonary hemorrhage that required discontinuation of ECMO. The patient died shortly after decannulation. Most literature suggests that PIG is one of the few pediatric interstitial lung diseases that has a favorable prognosis with rare mortality in the absence of co-morbidities. However, the current case suggests prognosis may depend more on the underlying diagnosis than on the histological finding of PIG. In addition, this case may provide insight into the pathogenesis and potential modifiers of this idiopathic disorder.

New Entities and Diagnostic Challenges in Pediatric Lung Disease

The differential diagnosis of diffuse lung disease in children differs considerably from adults, and analysis of pediatric lung biopsies may prove challenging for pathologists with more extensive exposure to adult lung biopsies. Biopsy diagnosis of pediatric lung disease continues to evolve as new pathologic entities are recognized and new genetic determinants of disease are discovered. This article describes the clinical characteristics, pathologic features, and differential diagnosis of challenging and recently described entities in pediatric lung disease. The specific entities discussed include alveolar capillary dysplasia, genetic disorders of surfactant metabolism, pulmonary interstitial glycogenosis, and neuroendocrine cell hyperplasia of infancy.

Pulmonary interstitial glycogenosis in the setting of lung growth abnormality: radiographic and pathologic correlation

Pulmonary interstitial glycogenosis (PIG) is a rare pediatric interstitial lung disease. We report a case of a term boy presenting with tachypnea at birth requiring supplemental oxygen. Chest radiographs followed by high-resolution CT (HRCT) demonstrated hyperinflation and diffuse interstitial markings interspersed with multiple cystic spaces. An open lung biopsy demonstrated a minor component of PIG superimposed upon poor alveolarization. PIG in the setting of lung growth abnormality might be more common than previously described. Additionally, radiographic findings associated with most pediatric interstitial lung diseases are nonspecific, and histopathologic correlation is essential for diagnosis.

Interstitial lung diseases in children

Interstitial lung disease (ILD) in infants and children comprises a large spectrum of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. These disorders are characterized by inflammatory and fibrotic changes that affect alveolar walls. Typical features of ILD include dyspnea, diffuse infiltrates on chest radiographs, and abnormal pulmonary function tests with restrictive ventilatory defect and/or impaired gas exchange. Many pathological situations can impair gas exchange and, therefore, may contribute to progressive lung damage and ILD. Consequently, diagnosis approach needs to be structured with a clinical evaluation requiring a careful history paying attention to exposures and systemic diseases. Several classifications for ILD have been proposed but none is entirely satisfactory especially in children. The present article reviews current concepts of pathophysiological mechanisms, etiology and diagnostic approaches, as well as therapeutic strategies. The following diagnostic grouping is used to discuss the various causes of pediatric ILD: 1) exposure-related ILD; 2) systemic disease-associated ILD; 3) alveolar structure disorder-associated ILD; and 4) ILD specific to infancy. Therapeutic options include mainly anti-inflammatory, immunosuppressive, and/or anti-fibrotic drugs. The outcome is highly variable with a mortality rate around 15%. An overall favorable response to corticosteroid therapy is observed in around 50% of cases, often associated with sequelae such as limited exercise tolerance or the need for long-term oxygen therapy.

Imaging of Childhood Interstitial Lung Disease

The aphorism that children are not little adults certainly applies for the imaging of interstitial lung disease. Acquiring motion-free images of fine pulmonary structures at desired lung volumes is much more difficult in children than in adults. Several forms of interstitial lung disease are unique to children, and some forms of interstitial lung disease encountered in adults rarely, if ever, occur in children. Meticulous attention to imaging technique and specialized knowledge are required to properly perform and interpret chest imaging studies obtained for the evaluation of childhood interstitial lung disease (chILD). This review will address technique recommendations for imaging chILD, the salient imaging findings in various forms of chILD, and the efficacy of imaging in the diagnosis and management of chILD.

Infants and Young Children with Children's Interstitial Lung Disease

Though interstitial lung disease (ILD) can occur at any age in children, disorders more common in infancy and young children have received increased attention as an important group that is disproportionally affected, linked to lung development and lung injury, and represents disorders not seen in adult ILD. Identifying those children with potential children's ILD (chILD) and establishing a specific chILD diagnosis has evolved and is critical for pediatric pulmonologists, neonatologists, radiologists, and pathologists to recognize. Specific disorders more common in infancy include diffuse developmental disorders, growth abnormalities, pulmonary interstitial glycogenosis, neuroendocrine cell hyperplasia of infancy, and surfactant mutation dysfunction mutations. The presentation, evaluation, treatment, and clinical course are discussed for each of these specific disorders and other categories less common in infants and young children are briefly mentioned. Resources for physicians and families are also reviewed.

Diagnostic Pathology of Diffuse Lung Disease in Children

The pathologic classification of diffuse lung disease in children and adolescents has undergone revision in recent years in response to rapid developments and new discoveries in the field. A number of important advancements have been made in the last 10 years including the description of new genetic mutations causing severe lung disease in infants and children, as well as the description of new pathologic entities in infants. These recently described entities, including ABCA3 surfactant disorders, pulmonary interstitial glycogenosis, and neuroendocrine cell hyperplasia of infancy, are being recognized with increasing frequency. This review will include brief discussion of the etiology and pathogenesis of the major groups of diffuse lung disease in children. Histopathologic features are discussed for each of the major categories of diffuse lung disease in children, beginning with the genetic, developmental, and alveolar growth disorders common in infancy, followed by brief discussion of airway diseases, immunologic diseases, and pulmonary vascular diseases seen more commonly in older children. A protocol for handling pediatric wedge lung biopsies is also discussed, which optimizes the diagnostic yield of lung biopsies in this population.

Pulmonary interstitial glycogenosis

Although bronchopulmonary dysplasia (BPD) is a common cause of interstitial lung disease in chronically intubated premature neonates, other interstitial lung disease in nonintubated infants is rare. We present a case of pulmonary interstitial glycogenosis that developed in a nonintubated, 31-week gestation infant in whom infectious etiologies had been excluded. The infant was well initially and then developed respiratory distress at 18 days of life. Radiographs at first day of life were normal, but CT and radiographic findings at 18 days of life showed severe interstitial lung disease, mimicking BPD. Lung biopsy showed pulmonary interstitial glycogenosis. This entity is not well described in the pediatric radiology literature and is important to consider, as the condition is responsive to a course of corticosteroids.

Chronic interstitial lung diseases in children

Interstitial lung diseases (ILDs) in children constitute a heterogeneous group of rare diseases that have been described and classified according to experiences and research in adults. However, pediatric pulmonologists have observed that the clinical spectrum is broader in children than in adults, and that many of these disorders have different courses and treatment responses. In addition, probably due to the various stages of lung development and maturation, new clinical forms have been described, particularly in infants. This has broadened the classification of ILDs in this age bracket. The understanding that neither the usual definition nor the standard classification of these disorders entirely apply to children has prompted multicenter studies designed to increase knowledge of these disorders, as well as to standardize diagnostic and therapeutic strategies. We have reviewed the conceptualization of ILDs in children, taking into consideration the particularities of this group of patients when using the criteria for the classification of these diseases in adults. We have also made a historical review of several multicenter studies in order to further understanding of the problem. We have emphasized the differences in the clinical presentation, in an attempt to highlight knowledge of newly described entities in young children. We underscore the need to standardize management of laboratory and radiological routines, as well as of lung biopsy processing, taking such knowledge into account. It is important to bear in mind that, among the recently described disorders, genetic surfactant dysfunction, which is often classified as an idiopathic disease in adults, should be included in the differential diagnosis of ILDs.

Diffuse lung disease in infancy: a proposed classification applied to 259 diagnostic biopsies

Thoracoscopic and open lung biopsies are being performed with increasing frequency in neonates and infants and are an important component of the diagnostic evaluation of respiratory compromise in these very young children. Diffuse lung disease in infancy includes a wide spectrum of developmental, genetic, inflammatory, infectious, and reactive disorders. The majority of the entities diagnosed in infancy (68%) in this retrospective lung biopsy series are seen almost exclusively in this age group and not in older children and adults. These include primary disorders of pulmonary and pulmonary vascular development, secondary disorders affecting prenatal and/or postnatal lung growth, genetic disorders of surfactant function, pulmonary interstitial glycogenosis, and neuroendocrine cell hyperplasia of infancy. Although the diagnostic approach to infant lung biopsies is guided primarily by the clinical history and imaging findings, all cases require careful assessment of alveolar growth, vascular architecture, interstitial cellularity, and histologic patterns associated with genetic abnormalities of surfactant metabolism. Recognition of one or more of these processes assists not only in treatment planning but also in further diagnostic evaluation and prognostication and may have implications for subsequent siblings and other family members. In this study, we have applied a classification system developed by a North American multicenter multidisciplinary group to lung biopsies seen at our institution and have used this material to describe and illustrate the spectrum of diffuse lung disease in infancy.

Histologic resolution of pulmonary interstitial glycogenosis

Pulmonary interstitial glycogenosis (PIG) is an enigmatic lung disorder of unknown etiology that presents with neonatal respiratory distress. Despite its dramatic clinical presentation, the diagnosis of PIG has a favorable prognosis with rare mortality in the absence of comorbid conditions. In this report, we describe changes in successive lung biopsies in a neonate who presented with respiratory failure and pulmonary hypertension. Diagnostic lung biopsy at 10 days of age exhibited classic histologic and ultrastructural findings of PIG with diffuse expansion of the alveolar interstitium by glycogenated mesenchymal cells. Subsequent to the patient's clinical improvement, a repeat biopsy at 49 days of age showed significant resolution of the disorder. Colocalization of vimentin-immunopositive cells with both phospho-histone H3 and cleaved caspase-3 demonstrated prominent attenuation of mesenchymal cell proliferation and apoptosis in the second biopsy. Although the self-limited nature of PIG has been described clinically, it has never been documented histologically. We present this case to illustrate the clinical and pathologic resolution of the disorder and speculate that the lesional mesenchymal cells may have transient proliferative capacity.