Short-limb skeletal dysplasia with severe combined immunodeficiency

Short-limb skeletal dysplasia with severe combined immunodeficiency (SCID), also known as immunodeficiency with short-limbed dwarfism or cartilage-hair hypoplasia (CHH) spectrum disorder, is a rare inherited condition that affects both the skeletal system and the immune system. The condition is characterized by disproportionate short stature due to shortening of the limbs (short-limbed dwarfism), along with a profoundly compromised immune system. Affected individuals typically present at birth or in early infancy with short limbs, metaphyseal dysplasia of the long bones, and features of severe combined immunodeficiency including markedly reduced or absent T-cell and B-cell function. This leaves patients extremely vulnerable to recurrent, severe, and life-threatening infections from bacterial, viral, and fungal pathogens. The skeletal features include short limbs with metaphyseal chondrodysplasia, fine and sparse hair (hypotrichosis), and ligamentous laxity. Additional features may include anemia (particularly macrocytic anemia), Hirschsprung disease, and an increased susceptibility to certain malignancies, particularly lymphoma. The condition is most commonly associated with mutations in the RMRP gene, which encodes the RNA component of the mitochondrial RNA-processing endoribonuclease complex, essential for cell growth and division in both cartilage and immune cells. Treatment focuses on managing the immunodeficiency and skeletal complications. Hematopoietic stem cell transplantation (HSCT) is the primary curative treatment for the immune deficiency component and should be performed early in life to prevent life-threatening infections. Supportive care includes infection prophylaxis, immunoglobulin replacement therapy, and orthopedic management for skeletal abnormalities. Without immune reconstitution through transplantation, the prognosis is poor due to overwhelming infections. Long-term follow-up is essential for monitoring growth, immune function, and cancer surveillance.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Short-limb skeletal dysplasia with severe combined immunodeficiency