Electron microscopy in the diagnosis of pediatric disease

Use of electron microscopy when screening liver biopsies from neonates and infants: experience from a single tertiary children's hospital (1991-2017)

Background: Although the role of electron microscopy is diminishing in several areas of adult pathology, it remains an essential tool for the study of pediatric liver biopsies.Methods: Clinical charts, histologic slides and EM materials of native liver biopsies from patients <1 year old (1991-2017) were reviewed.Results: 677 biopsies were performed on 353 males and 324 females. This study presents the concrete numbers for both the indications and the diseases, and describes the role of EM. EM was performed on 24.7% of liver biopsies and demonstrated key pathologic findings in 10 cases (6%), which led to the appropriate biochemical and/or genetic testing to confirm the diagnoses. The cases included five cases of glycogen storage disease with characteristic findings with cytoplasmic glycogen accumulation, two cases of mitochondrial disorder with pleomorphic mitochondria with crystalloid inclusions and one case each of Niemann-Pick Disease with abundant myelinosomes, Alpha-1 antitrypsin deficiency with deposits in the endoplasmic reticulum and infantile Refsum disease with trilamellar inclusions and lack of peroxisomes. In this study, we describe the detailed histologic and EM findings of each case .Conclusion: EM played an important screening and diagnostic role in the challenging cases and was also used to rule out detectable pathologic conditions.

Ultrastructural examination of the axillary skin biopsy in the diagnosis of metabolic diseases

There is little information in the literature regarding the usefulness of ultrastructural examination of axillary skin biopsies in the evaluation of metabolic diseases. This is a retrospective clinicopathologic review of 143 patients who underwent axillary skin biopsies as part of evaluations for metabolic disease. Twenty-three (16%) had abnormalities, classified as follows: mitochondrial (n = 12), lysosomal (n = 6), increased glycogen (n = 3), nonspecific cytoplasmic inclusions (n = 2), ceroid lipofuscinosis (n = 1), and intradermal giant cells containing vacuoles and tubular inclusions (n = 1). Muscle biopsies were performed in 13 of the 23 patients; 11 showed abnormalities, including those related to mitochondria (n = 4) and other nonspecific changes (n = 7). Two patients underwent postmortem examination. Follow-up was available in 21 patients. A clinical or biochemical diagnosis was reached in 11 patients: metachromatic leukodystrophy (n = 2), electron transport chain abnormalities (n = 2), glutaric aciduria type II (n = 1), Unverricht disease (n = 1), Lennox-Gastaut syndrome (n = 1), ketotic hypoglycemia of childhood (n = 1), probable Leigh disease (n = 1), 5-methyl tetrahydrofolate homocystine methyltransferase deficiency (n = 1), and pyruvate dehydrogenase deficiency (n = 1). Of the 120 patients with negative skin biopsy results, 29 had abnormal findings on muscle (n = 27), nerve (n = 7), or brain (n = 3) biopsies. One patient had an abnormal heart biopsy result, and 3 patients underwent postmortem examinations. Follow-up was obtained in 27 of 29 patients. Diagnoses were achieved in 15 patients: electron transport chain abnormalities (n = 5), cortical dysplasia (n = 3), myoclonic epilepsy (n = 1), leukodystrophy (n = 2), Pallister-Killian mosaic syndrome (n = 1), Rett syndrome (n = 1), Landau-Kleffner syndrome (n = 1), and mitochondrial cardiomyopathy (n = 1). In conclusion, axillary skin biopsy is helpful in the evaluation of some causes of metabolic disease, but often the findings are nonspecific. A negative biopsy result does not rule out the possibility of metabolic disease, but a positive result may provide direction for further evaluation.

The pathologist's approach to the diagnosis of metabolic disease

Many inborn errors of metabolism have tissue changes that suggest or indicate a diagnosis on morphologic bases. This emphasizes the involvement of the pathologist in the study of tissues obtained by biopsy as part of the diagnostic workup of cases with clinical evidence suggesting a metabolic disorder. Some of these diseases involve proteins with enzymatic activity with a consequent backlog of precursor metabolites. If these metabolites are insoluble or compartmentalized in cells, they accumulate in tissues. The diagnosis in those cases rests on establishing the nature of the accumulated materials and their topographic distribution. In some storage diseases, the abnormal substance can be identified in the affected tissues by histochemistry or ultrastructure. Another group of inborn disorders of metabolism produce changes in subcellular organelles such as peroxisomes and mitochondria. A third group is expressed by rather unique tissue changes which strongly suggest the diagnosis of metabolic disease.