Patients are evaluated annually or biannually, depending on disease status and progression. Patients undergo a complete medical history, an extensive family pedigree, and a physical examination. Patients undergo general laboratory, imaging, physiologic, and clinical laboratory studies according to their disease type. Patients undergo specialized laboratory studies including plasma and leukocyte enzyme assays, quantitative urinary mucopolysaccharides and oligosaccharides, urine and plasma glycolipids, plasma and urine amino acids, urine organic acids, lymphoblastoid culture, DNA isolation from peripheral leukocytes, skin biopsy for fibroblast culture (if indicated), and medical photography. Patients also receive consultations with various specialties including ophthalmology, ENT, cardiology, pulmonary, gastroenterology/nutrition, hematology, neurology, orthopedics, rehabilitation medicine/physical therapy, and dermatology.