Sly syndrome, also called Mucopolysaccharidosis Type VII or MPS, was named after its discoverer William Sly in 1969. 
Sly syndrome is an autosomal recessive lysosomal storage disease characterized by a deficiency of the enzyme β-glucuronidase, a lysosomal enzyme. Sly syndrome belongs to a group of disorders known as the mucopolysaccharidoses, which are lysosomal storage diseases. In Sly syndrome, the deficiency in β-glucuronidase leads to the accumulation of certain complex carbohydrates (mucopolysaccharides) in many tissues and organs of the body.
The defective gene responsible for Sly syndrome is located on chromosome 7.
The symptoms of Sly syndrome are similar to those of Hurler syndrome (MPS I). The symptoms include:
in the head, neck, and face: coarse (Hurler-like) facies and macrocephaly, frontal prominence, premature closure of sagittal lambdoid sutures, and J-shaped sella turcica
in the eyes: corneal opacity and iris colobmata
in the nose: anteverted nostrils and a depressed nostril bridge
in the mouth and oral areas: prominent alveolar processes and cleft palate
in the thorax: usually pectus carinatum or exacavatum and oar-shaped ribs; also a protruding abdomen and inguinal or umbilical hernia
in the extremities: talipes, an underdeveloped ilium, aseptic necrosis of femoral head, and shortness of tubular bones occurs
in the spine: kyphosis or scoliosis and hook-like deformities in thoracic and lumbar vertebrate
in the bones: dysotosis multiplex
In addition recurrent pulmonary infections occur. Hepatomegaly occurs in the gastrointestinal system. Splenomegaly occurs in the hematopoietic system. Inborn mucopolysaccharide metabolic disorders due to β-glucuronidase deficiency with granular inclusions in granulocytes occurs in the biochemical and metabolic systems. Growth and motor skills are affected, and mental retardation also occurs.
MPS type VII occurs in only 1:250,000 people.
Mucopolysaccahridosis Type VII is also known as β-glucurondinase deficiency, β-glucurondinase deficiency mucopolysaccahridosis,
GUSB deficiency, mucopolysaccahride storage disease VII, MCA, and MR.
^ Sly WS, Quinton BA, McAlister WH, Rimoin DL (1973). "Beta glucuronidase deficiency: report of clinical, radiologic, and biochemical features of a new mucopolysaccharidosis". J. Pediatr.82 (2): 249–57. PMID 4265197.