The first two images (Fig 1 and Fig 2) in this case reveal widespread pulmonary interstitial disease characterized by a diffuse distribution of cystic spaces with slightly thickened walls (which produce a "honeycomb" pattern) and a fat-density mass in the liver. The diagnosis is confirmed by the second two images (Fig 3 and Fig 4), which show innumerable cysts and  fatty tumors in the kidneys along with periventricular calcifications.

Figure 3	Figure 4

Tuberous sclerosis is an uncommon inherited disease. Its mode of inheritance is autosomal dominant but at least two thirds of the cases arise from spontaneous mutations.  The abnormal genes are found on chromosomes 9 and 16; one of these is adjacent to the gene which produces autosomal dominant polycystic renal disease, and these two diseased share the feature of multiple renal cysts.

The abnormal genes are tumor suppressor genes; they lead to abnormalities of cell growth and migration which in turn lead to an extremely wide variety of abnormalities although frank malignancies are rare. Dermal lesions include facial angiofibromas, periungual fibromas, shagreen patches, cafe-au-lait spots, and hypomelanotic ("ash-leaf") spots.

This condition used to be known as Bourneville's disease, and the original diagnostic triad was adenoma sebaceum, mental retardation, and seizures. Currently, the disease is characterized by a much wider variety of lesions; several combinations of lesions suffice to make the diagnosis. 

Tuberous sclerosis is a neurocutaneous syndrome, or phacomatosis. It may be diagnosed prenatally, in childhood, or early adulthood, and is predominantly found in females. Lesions may appear in the central nervous system, skin, retina, lungs, bones, heart, kidney, liver, and uterus. The radiological diagnosis is made by observing some combination of findings, including subependymal and periventricular calcifications, cortical tubers, cardiac tumors, renal cysts, and angiomyolipomas.

Cerebral manifestations include cortical tubers, which are macroscopic nodules or protrusions which usually arise in or between the cortical gyri. These protrusions contain atypical giant astrocytes, abnormal neurons, and regions of gliosis and abnormal myelinization; uncommonly, they occur in the cerebellum.  The tubers are difficult to see on CT;  MRI reveals them even though they are nearly isointense to adjacent tissue on both T1-and T2-weighted images. They are  associated with local diminution in the normal gray-white matter differentiation.

Also present in tuberous sclerosis are subependymal hamartomatous nodules, which often calcify. Occasionally a giant cell astocytoma may appear, and this frequently causes obstruction of the foramen of Monro.

In the kidney, multiple angiomyolipomas are common, as are cysts. The cysts may predominate, and this may produce confusion when differentiating tuberous sclerosis from other polycystic renal diseases. Cysts occasionally also appear in the liver, pancreas, and spleen. The tumors are virtually always diagnosed by demonstrating internal fat with CT or MRI. Diagnostic angiography is no longer employed, but, when it was used, it revealed multiple large irregular vessels with frequent small aneurysms. The angiomyolipomas in the kidney may appear as small scattered tumors, or may be so numerous and voluminous that the kidneys are swollen and distorted almost beyond recognition. Angiomyolipomas have been reported in the liver, as can be seen in this case, but the association of hepatic angiomyolipoma with tuberous sclerosis is not well established.

Cardiac rhabdomyomas occasionally appear with this disease and they are often diagnosed perinatally. There are also skeletal lesions, which include small sclerotic regions and bone cysts. Hamartomatous polyps may appear anywhere in the GI tract from the esophagus to the rectum.

Pulmonary lymphangioleiomyomatosis may appear, either with other signs of tuberous sclerosis or as an isolated disease. It almost always appears in young women. The primary abnormality is a proliferation of abnormal smooth muscle cells, which may appear in the pulmonary interstitium, in the lymphatics, or in associated nodes. Radiologically, a reticular interstitial pattern appears which ultimately progresses until uniformly distributed small cyst-like structures occupy the entirety of the lung volume and produce a "honeycomb lung" appearance. This may be visualized both radiographically and by CT. Pulmonary function is severely compromised and sometimes requires transplantation.

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