Keratosis follicularis spinulosa decalvans (KFSD) is an X-linked condition characterized by keratotic follicular papules and progressive alopecia, which is caused by mutations in the MBTPS2 gene. We carried out a genetic study on a child who was suspected clinically to have KFSD. Sanger sequencing was performed to detect mutations in the entire coding region of MBTPS2. A novel missense mutation (c.599C>T) was identified in the patient, confirming a diagnosis of KFSD. We reviewed related cases with MBTPS2 mutations for evidence of genotype-phenotype correlations.