Ultrastructure of Leydig cells in Klinefelter’s syndrome with 48, XXYY karyotype

Abstract

The most relevant abnormal ultrastructural features of a testicular biopsy from a patient with the 48 XXYY variant of Klinefelter’s syndrome were found in the Leydig cells, in relation to the organelles involved in steroid production. The well developed smooth endoplasmic reticulum, occupying the major part of the cytoplasm, was made up of a tubular or vesicular network as well as multilayered concentric unfenestrated cisternae. These cisternae surrounded tubules or vesicles of smooth endoplasmic reticulum as well as mitochondria, lipid droplets, lysosomes and other cytoplasmic organelles. The generally numerous mitochondria varied in size, shape and inner structure. Rod-shaped or ovoid, large mitochondria, exhibiting tubular and/or lamellar cristae, were abundant. They often contained lipid droplets and myelin-like figures. Primary lysosomes were frequently seen, but secondary lysosomes and lipofuchsin pigments were not apparent. Lipid droplets and Reinke’s crystalloids were scanty. Microcrystalline inclusions were frequent. Numerous microfilaments were scattered, either singly or in bundles, in the cytoplasm. In some cells, the bundles of microfilaments were arranged in a manner simulating crystalline inclusions. Adjacent cells were joined by cytoplasmic interdigitations and gap junctions. The functional signification of the organelles in relation to steroid biosynthesis is discussed.