Table 7.
| Disease | Distinct differences with HFTC |
| Calcinosis universalis | Calcium depositions in tendons and muscle tissues Normophosphatemia High hemosedimentation Microcytic and hypochromic anemia |
| Calcinosis circumscripta | Adult onset Local calcinosis Fingers symmetrically affected |
| Calcific tendinitis | Adult onset Calcification limited to tendons |
| Synovial chondromatosis | Lesions arising from synovial tissue Widespread throughout the body Not all lesions are calcified |
| Osteosarcoma | Long bone malignant tumor 2nd life decade or late adulthood No subcutaneous/skin lesions |
| Fibrodysplasia ossificans progressiva (AD; ACVR1 gene) | Hallux valgus, monophalangism and/or malformed first metatarsal Sporadic episodes of painful soft tissue swellings (flare-ups) in 1st life decade |
| Tophaceous gout | Severe form of gout Severe joint deformity, chronic pain and functional decline More prominent in Asian population (slow metabolizers) and in young men with strong genetic predisposition |
| Calcific myonecrosis | Post-traumatic (time interval of several years possible) Lower limbs only |
| NFTC (AR; SAMD9 gene) | Reddish-to-hyperpigmented skin lesions during the first year of life (preceding calcified nodules) Severe conjunctivitis and gingivitis Normophosphatemia |
| Secondary tumoral calcinosis | Renal insufficiency, hyperparathyroidism, or hypervitaminosis D |
| Rheumatological diseases | Usually normophosphatemia and - calcemia Possibly positive results in antinuclear, anti-Smith, anti-centromere and anti-scleroderma antibodies, which should all be negative |
ACVR1: Activin A receptor, type 1; AD: Autosomal dominant; AR: autosomal recessive; HFTC: Hyperphosphatemic familial tumoral calcinosis; NFTC: Normophosphatemic familial tumoral calcinosis; SAMD9: Sterile alpha motif domain-containing protein 9.