LAUSR

A 34-year-old woman developed severe low back pain 2 months after delivery by caesarean section, without any preceding trauma. She was a non-smoker, did not misuse alcohol, and had a history of cholecystitis and endometriosis. Her father, now 80 years old, has had autoimmune thyroiditis and severe osteoporosis with bone fractures from a young age. Her 72-year-old mother has a history of secondary osteoporosis due to primary hyperparathyroidism (parathyroid adenoma), deep vein thrombosis, pulmonary embolism, and hypertension. Her sister has been diagnosed with autoimmune thyroiditis and vitamin D deficiency. Physical examination revealed a youngwomanwithmild scoliosis but no other body abnormalities. Neurological examination was unremarkable. A lumbar spine X-ray revealed osteoporotic bones with multiple vertebral fractures of L1–L5 (Figure 1). Bone mass density (L1–L4) was measured as 0.713 g/cm with a Z-score of −3.9, which demonstrated the presence of severe vertebral osteoporosis. Thyroid and adrenal function tests, vitamin D and parathyroid hormone levels, liver function tests, autoantibodies specific for coeliac disease, and urinary 24 h calcium were all within normal limits. Since all causes that could be responsible for premenopausal osteoporosis were excluded, osteogenesis imperfecta (OI) was suspected. Whole-exome sequencing analysis with the Illumina NextSeq-500 system detected a heterozygous mutation in the collagen type II alpha-1 chain (COL2A1) gene on chromosome 12 (12q13.1), exon 45. A nucleotide replacement of c.3136C>T, which causes an amino acid replacement p. Pro1046Ser, was found (1, 2). Type II collagen provides strength to the structure and integrity of connective tissues such as muscles, joints, and skin. Collagen type II mutations are expressed in clinical syndromes called collagenopathies, which include achondrogenesis, spondyloepiphyseal dysplasia, Kniest dysplasia, and Stickler’s syndrome. Apart from severe osteoporosis and vertebral fractures, our patient did not express other characteristics of the above syndromes, such as facial deformities, short stature, deformed arms and legs, barrel-shaped chest, or hearing or visual losses. Given that the patient’s father had a history of severe osteoporosis and spontaneous fractures without an identifiable underlying cause, it is suspected that the patient’s pathology may be due to a genetic collagen defect transmitted from her father with an autosomal dominant trait. This phenotype of the collagen II mutation has not been previously correlated with only severe osteoporosis or osteogenesis imperfecta. We present this case to alert the medical community to the association of a collagen II mutation with severe