ICD-10-CM 2027
ICD-10 code for skull hyperostosis
From the official ICD-10-CM alphabetic index entry “Hyperostosis (monomelic) › skull”. Page updated September 29, 2026.
About coding skull hyperostosis
The ICD-10-CM code for skull hyperostosis is M85.2 (Hyperostosis of skull). The official index lists 1 more specific code, so check the documentation for details such as type, cause, site or severity before settling on M85.2.
Within M85 (other disorders of bone density and structure), M85.2 is specifically for hyperostosis of skull. Related codes cover fibrous dysplasia (monostotic) (M85.0), skeletal fluorosis (M85.1), Osteitis condensans (M85.3), Solitary bone cyst (M85.4), Aneurysmal bone cyst (M85.5), other cyst of bone (M85.6), other specified disorders of bone density and structure (M85.8) and disorder of bone density and structure, unspecified (M85.9).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 564 (Other Musculoskeletal System and Connective Tissue Diagnoses with MCC, relative weight 1.4908), DRG 565 (Other Musculoskeletal System and Connective Tissue Diagnoses with CC, relative weight 0.9783) and DRG 566 (Other Musculoskeletal System and Connective Tissue Diagnoses without CC/MCC, relative weight 0.7378), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific skull hyperostosis codes (official index)
- congenital Q75.8 — Other specified congenital malformations of skull and face bones
Common questions about skull hyperostosis ICD-10 codes
What is the ICD-10 code for skull hyperostosis?
- M85.2 — Hyperostosis of skull. More specific codes apply when the documentation supports them: Q75.8.
What is the ICD-10 code for congenital skull hyperostosis?
- Q75.8 — Other specified congenital malformations of skull and face bones.
Is M85.2 billable?
- Yes. M85.2 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can M85.2 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict M85.2 as a principal diagnosis.
Is M85.2 a CC or MCC?
- No. M85.2 is neither a CC nor an MCC under MS-DRG v44.0.