Schimke Immunoosseous Dysplasia

Clinical characteristics Schimke immunoosseous dysplasia (SIOD) is an autosomal recessive multisystem disorder characterized by spondyloepiphyseal dysplasia (SED) resulting in short stature, nephropathy, and T-cell deficiency. Radiographic manifestations of SED include ovoid and mildly flattened vertebral bodies, small deformed capital femoral epiphyses, and shallow dysplastic acetabular fossae. Adult height is 136-157 cm for men and 98.5-143 cm for women. Nearly all affected individuals have progressive steroid-resistant nephropathy, usually developing within five years of the diagnosis of growth failure and terminating with end-stage renal disease (ESRD). The majority of tested individuals have T-cell deficiency and an associated risk for opportunistic infection, a common cause of death. SIOD involves a spectrum that ranges from an infantile or severe early-onset form with death early in life to a juvenile or milder later-onset form with survival into adulthood if renal disease is appropriately treated. Diagnosis/testing The diagnosis of SIOD is established in a proband with the characteristic clinical and radiographic features. Identification of biallelic pathogenic variants in SMARCAL1 on molecular genetic testing establishes the diagnosis if clinical features are inconclusive. Management Treatment of manifestations: Renal transplantation as indicated using mild immunosuppressive therapy; hip replacement as needed in older individuals; granulocyte colony-stimulating factor or granulocyte-macrophage colony-stimulating factor for neutropenia; bone marrow transplantation as indicated; immunosuppressive therapy for those with autoimmune manifestations; acyclovir for recurrent herpetic infections; imiquimod and cidofovir for severe disseminated cutaneous papilloma virus infections; agents that improve blood flow or decrease coagulability to treat transient ischemic attacks or strokes; standard treatment for hypothyroidism. Prevention of secondary complications: Vaccinations according to the protocol for other T-cell immunodeficiencies (i.e., an avoidance of live attenuated vaccines) in individuals with severe early-onset disease; prophylaxis against Pneumocystis jirovecii pneumonia; prophylactic acyclovir or valacylovir if recurrent oral herpetic infections or shingles occur. Surveillance: Regular monitoring of the hips; annual monitoring of renal, immune, and hematologic status. Agents/circumstances to avoid: Hypertension; heat, stress, and lack of sleep; live attenuated immunizations in those who are T-cell deficient; DNA damaging anti-cancer therapies. Genetic counseling SIOD is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing and prenatal testing are possible if both pathogenic variants in the family are known.