Infantile systemic hyalinosis

Infantile systemic hyalinosis is a disorder that severely affects many areas of the body, including the skin, joints, bones, and internal organs. Hyalinosis refers to the abnormal accumulation of a clear (hyaline) substance in body tissues. The signs and symptoms of this condition are present at birth or develop within the first few months of life. Infantile systemic hyalinosis is characterized by painful skin bumps that frequently appear on the hands, neck, scalp, ears, and nose. They also develop in joint creases and the genital region. These skin bumps may be large or small and often increase in number over time.

Lumps of noncancerous tissue also form in the muscles and internal organs of children with infantile systemic hyalinosis, causing pain and severe complications. Most affected individuals develop a condition called protein-losing enteropathy due to the formation of lumps in their intestines. This condition results in severe diarrhea, failure to gain weight and grow at the expected rate (failure to thrive), and general wasting and weight loss (cachexia).

Infantile systemic hyalinosis is also characterized by overgrowth of the gums (gingival hypertrophy). Additionally, people with this condition have joint deformities (contractures) that impair movement. Affected individuals may grow slowly and have bone abnormalities.

Although children with infantile systemic hyalinosis have severe physical limitations, mental development is typically normal. Affected individuals often do not survive beyond early childhood due to chronic diarrhea and recurrent infections.

The prevalence of infantile systemic hyalinosis is unknown. Fewer than 20 people with this disorder have been reported.

Mutations in the ANTXR2 gene (also known as the CMG2 gene) cause infantile systemic hyalinosis. The ANTXR2 gene provides instructions for making a protein involved in the formation of tiny blood vessels (capillaries). Researchers believe that the ANTXR2 protein is also important for maintaining the structure of basement membranes, which are thin, sheet-like structures that separate and support cells in many tissues.

The signs and symptoms of infantile systemic hyalinosis are caused by the accumulation of a hyaline substance in different parts of the body. The nature of this substance is not well known, but it is likely made up of protein and sugar molecules. Researchers suspect that mutations in the ANTXR2 gene disrupt the formation of basement membranes, allowing the hyaline substance to leak through and build up in various body tissues.

Read more about the ANTXR2 gene.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.