Laboratory Studies
Definitive diagnosis of sialidosis is made by demonstrating a deficiency of alpha-N -acetyl neuraminidase activity, which can be measured in amniocytes, leukocytes, and cultured fibroblasts. The finding of pathologic mutations in NEU1 is an alternate method to diagnose this disease and offers the ability for reliable detection of heterozygous carriers for genetic counseling of family members. Detection of an abnormal pattern of urinary oligosaccharides can be used as an initial screening test.
Imaging Studies
The characteristic bone changes are similar to but not as severe as those observed in the mucopolysaccharidoses. The classic radiographic finding is dysostosis multiplex. This may be observed as anterior beaking of the vertebral bodies, widening of the ribs, hypoplastic ilia, and expanded metacarpal and phalangeal shafts. Radiographs obtained early in the course of the disease may reveal only stippling of the epiphyses.
The literature has described 4 cases of femur head necrosis, which might be an early manifestation of late-onset sialidosis. [8]
Other Tests
Renal function evaluation and serial urinary protein evaluation are indicated.
Histologic Findings
Cytoplasmic vacuolation of varying degrees has been observed and reported in peripheral lymphocytes, bone marrow cells, conjunctival epithelium, Kupffer cells, hepatocytes, tissue fibroblasts, nerve biopsy specimens, myenteric plexus neurons, and brain biopsy material. Using electron microscopy, membrane-bound vacuoles containing flocculent or reticulogranular material have been described. [9]
