Monogenic lupus due to spondyloenchondrodysplasia with spastic paraparesis and intracranial calcification: case-based review.

Spondyloenchondrodysplasia (SPENCD) is a rare skeletal dysplasia characterized with platyspondyly and metaphyseal lesions of the long bones mimicking enchondromatosis, resulting in short stature. SPENCD often coexists with neurologic disorders and immune dysregulation. Spasticity, developmental delay and intracranial calcification are main neurologic abnormalities. Large spectrum of immunologic abnormalities may be seen in SPENCD, including immune deficiencies and autoimmune disorders with autoimmune thrombocytopenia and systemic lupus erythematosus as the most common phenotypes. SPENCD is caused by loss of tartrate-resistant acid phosphatase (TRAP) activity, due to homozygous mutations in ACP5, playing a role in non-nucleic acid-related stimulation/regulation of the type I interferon pathway. We present two siblings, 13-year-old girl and 25-year-old boy with SPENCD, from consanguineous parents. Both patients had short stature, platyspondyly, metaphyseal changes, spastic paraparesis, mild intellectual disability, and juvenile-onset SLE. The age at disease-onset was 2 years for girl and 19 years for boy. Both had skin and mucosa involvement. The age at diagnosis of SLE was 4 years for girl, and 19 years for boy. The clinical diagnosis of SPENCD was confirmed by sequencing of ACP5 gene, which revealed a homozygous c.155A > C (p.K52T), a variant reported before as pathogenic. Juvenile-onset SLE accounts for about 15-20% of all SLE cases. But, the onset of SLE before 5-years of age and also monogenic SLE are rare. Our case report and the literature review show the importance of multisystemic evaluation in the diagnosis of SPENCD and to remind the necessity of investigating the monogenic etiology in early-onset and familial SLE cases.