| Disease entity / subtype | Key gene(s) | Inheritance | Example pathogenic variants | Core clinical phenotype | Key diagnostics | Mechanistic pathway / notes |
|---|---|---|---|---|---|---|
| Isolated woolly hair / autosomal recessive woolly hair-hypotrichosis (classic non-syndromic ARWH; includes ARWH1/2/3) | **LIPH**, **LPAR6/P2RY5**, **KRT25**; **C3ORF52** also reported in rare cases (pqac-00000001, pqac-00000005, pqac-00000006) | Usually **autosomal recessive** (pqac-00000001, pqac-00000002, pqac-00000003) | Representative recent/recurring variants: **LIPH c.736T>A (p.Cys246Ser)**, **c.742C>A (p.His248Asn)**, **c.1101del**, **c.530T>G (p.Leu177Arg)**; **LPAR6 c.436G>A (p.Gly146Arg)** (pqac-00000002, pqac-00000006, pqac-00000015, pqac-00000017, pqac-00000027) | Congenital or first 2 years; sparse, thin, tightly curled “woolly” scalp hair; fragility, slow growth, often stops at short length, rarely **>12 cm**; other ectodermal structures usually normal (pqac-00000001, pqac-00000003, pqac-00000006) | Clinical hair exam; trichoscopy (wavy/curly shafts, broken hairs, clumping, yellow/black dots); light microscopy; SEM showing rough/irregular cuticle, grooves, oval cross-sections; confirm with exome/panel testing and segregation (pqac-00000000, pqac-00000002, pqac-00000006) | Central axis: **LIPH → LPA → LPAR6/P2RY5**; proteins co-expressed in **inner root sheath (IRS)**; pathway supports IRS development, hair growth, and can signal via **EGFR**; loss of function impairs follicular differentiation/maturation (pqac-00000010, pqac-00000012, pqac-00000014, pqac-00000016) |
| ARWH2 / LIPH-related isolated woolly hair-hypotrichosis | **LIPH** (PA-PLA1α) (pqac-00000005, pqac-00000012) | Autosomal recessive (pqac-00000000, pqac-00000002) | **c.736T>A (p.Cys246Ser)** founder/recurrent in Japan; **c.742C>A (p.His248Asn)** founder/recurrent; **c.1101del** novel frameshift; **c.530T>G (p.Leu177Arg)** with secretion defect (pqac-00000002, pqac-00000006, pqac-00000015, pqac-00000017, pqac-00000023) | Since birth or infancy; short, sparse, brittle yellowish/rough hair, easy breakage; one case limited to ~**5 cm** growth (pqac-00000000, pqac-00000002, pqac-00000006) | WES/Sanger commonly diagnostic; SEM/trichoscopy often supportive (pqac-00000000, pqac-00000002, pqac-00000006) | LIPH encodes a phospholipase producing **lysophosphatidic acid (LPA)**; pathogenic variants can reduce catalytic activity or block secretion, causing loss of downstream **P2RY5/LPAR6** activation and defective hair development (pqac-00000012, pqac-00000015, pqac-00000017) |
| ARWH1 / LPAR6-related isolated woolly hair-hypotrichosis | **LPAR6 / P2RY5** (pqac-00000001, pqac-00000011, pqac-00000013) | Autosomal recessive (pqac-00000004, pqac-00000027) | **c.436G>A (p.Gly146Arg)** reported in Pakistani families; multiple other pathogenic LPAR6 variants known (pqac-00000004, pqac-00000022, pqac-00000027) | Early-onset sparse, woolly scalp hair, usually without ectodermal abnormalities (pqac-00000004, pqac-00000013) | Gene-focused sequencing or exome sequencing with segregation; clinical recognition of isolated scalp hair phenotype (pqac-00000001, pqac-00000004) | LPAR6 encodes an **LPA-responsive GPCR** critical for hair follicle morphogenesis and hair shaft differentiation; missense changes may disrupt transmembrane helix structure and receptor signaling (pqac-00000011, pqac-00000013) |
| ARWH3 / keratin-associated recessive woolly hair-hypotrichosis | **KRT25** (rare recessive cause); keratin genes also important in broader woolly hair biology (pqac-00000001, pqac-00000005, pqac-00000032) | Autosomal recessive for classic ARWH3; distinguish from dominant keratin-related woolly hair due to other keratins (pqac-00000001, pqac-00000005, pqac-00000007) | Specific recurrent KRT25 examples not detailed in available contexts here; reported founder variants noted in review literature (pqac-00000001) | Similar congenital woolly hair/hypotrichosis phenotype with variable severity (pqac-00000001, pqac-00000005) | Genetics is key because phenotype overlaps with LIPH/LPAR6 disease (pqac-00000001, pqac-00000005) | Keratin dysfunction affects **IRS/hair shaft structural integrity** and molding of the hair shaft (pqac-00000016, pqac-00000032) |
| Rare isolated ARWH-like form | **C3ORF52** (also TTMP) (pqac-00000005, pqac-00000010, pqac-00000015) | Autosomal recessive (bi-allelic loss-of-function reported) (pqac-00000005, pqac-00000010) | Specific variants not provided in available contexts (pqac-00000005, pqac-00000010) | Localized or generalized hypotrichosis/woolly hair reported in rare cases (pqac-00000001, pqac-00000014) | Detected by exome/panel sequencing when LIPH/LPAR6/KRT25 are negative (pqac-00000001, pqac-00000005) | C3ORF52 is membrane-localized, co-expressed with **PA-PLA1α/LPA6** in the **IRS**, and supports the same lipid signaling pathway required for hair growth (pqac-00000010, pqac-00000015) |
| Important differential / not classic isolated ARWH | **ADAM17** | **Autosomal dominant** hypotrichosis with woolly hair, not the usual recessive isolated ARWH category (pqac-00000033, pqac-00000034) | **c.1939G>A (p.Asp647Asn / p.D647N)** (pqac-00000034) | Hair loss/hypotrichosis with woolly hair phenotype; distinct from classic LIPH/LPAR6 recessive disease (pqac-00000033, pqac-00000034) | Human genetics plus supportive knock-in mouse model (pqac-00000033, pqac-00000034) | Variant enhances **TRIM47-mediated ubiquitination** and degradation of ADAM17, reducing **Notch** signaling and causing hair follicle stem-cell dysfunction; mechanistically relevant but separate disease class (pqac-00000033, pqac-00000034) |
| Population / recent epidemiology highlights | Mainly **LIPH** in Japan; **LPAR6** more sporadic globally (pqac-00000021, pqac-00000023, pqac-00000024) | AR inheritance enriched in consanguineous pedigrees for some populations (pqac-00000004, pqac-00000022) | Founder/recurrent variants: Japan **LIPH c.736T>A**, **c.742C>A**; Pakistan **LIPH c.659_660del** and recurrent **LPAR6 p.Gly146Arg**; Russia exon 4 **LIPH c.527_628del**; China 12/19 reported ARWH cases linked to **LIPH c.742C>A** (pqac-00000001, pqac-00000021, pqac-00000022, pqac-00000023) | Rare disorder overall; a 2025 review screened **63 English + 22 Chinese** articles; one estimate suggests **~10,000 Japanese patients** with LIPH-related ARWH due to founder alleles (pqac-00000001, pqac-00000023) | Population-aware variant interpretation and targeted testing can improve yield (pqac-00000021, pqac-00000023) | Founder effects are strong for **LIPH** in some populations, while **LPAR6** lacks a single dominant recurrent mutation across countries (pqac-00000021, pqac-00000024) |
| Current management evidence | No established disease-modifying therapy (pqac-00000018, pqac-00000020) | Not applicable | Topical **minoxidil** tried in at least one recent LIPH case without significant improvement after ~3 months; review literature mentions anecdotal minoxidil, gentamicin, regenerative, and plant-derived approaches (pqac-00000018, pqac-00000019, pqac-00000020) | Lifelong cosmetic/quality-of-life issue more than systemic morbidity in isolated forms (pqac-00000003, pqac-00000020) | Supportive dermatologic follow-up and genetic counseling; exclude syndromic woolly hair with cardiac/ectodermal involvement (pqac-00000007, pqac-00000020) | Future therapeutic concept is pathway-directed modulation of the **LIPH/LPA/LPAR6** axis rather than any validated targeted treatment at present (pqac-00000018, pqac-00000020) |


*Table: This table condenses the main clinical, genetic, mechanistic, diagnostic, and population-level facts for isolated woolly hair/autosomal recessive woolly hair-hypotrichosis. It distinguishes classic recessive forms from related but non-classic entities such as dominant ADAM17-associated woolly hair/hypotrichosis.*