Any hypotrichosis in which the cause of the disease is a mutation in the APCDD1 gene. The disease is hypotrichosis 1 (MONDO_0011549). Also known as: APCDD1 hypotrichosis, HTS, HYPT1, hereditary generalised hypotrichosis simplex, hereditary generalized hypotrichosis simplex, hypotrichosis caused by mutation in APCDD1, hypotrichosis type 1.